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* Sun Mar 12 2023 Miroslav Rezanina <mrezanin@redhat.com> - 7.2.0-12

Browse Source 
- kvm-scsi-protect-req-aiocb-with-AioContext-lock.patch [bz#2155748]
- kvm-dma-helpers-prevent-dma_blk_cb-vs-dma_aio_cancel-rac.patch [bz#2155748]
- kvm-virtio-scsi-reset-SCSI-devices-from-main-loop-thread.patch [bz#2155748]
- kvm-qatomic-add-smp_mb__before-after_rmw.patch [bz#2175660]
- kvm-qemu-thread-posix-cleanup-fix-document-QemuEvent.patch [bz#2175660]
- kvm-qemu-thread-win32-cleanup-fix-document-QemuEvent.patch [bz#2175660]
- kvm-edu-add-smp_mb__after_rmw.patch [bz#2175660]
- kvm-aio-wait-switch-to-smp_mb__after_rmw.patch [bz#2175660]
- kvm-qemu-coroutine-lock-add-smp_mb__after_rmw.patch [bz#2175660]
- kvm-physmem-add-missing-memory-barrier.patch [bz#2175660]
- kvm-async-update-documentation-of-the-memory-barriers.patch [bz#2175660]
- kvm-async-clarify-usage-of-barriers-in-the-polling-case.patch [bz#2175660]
- Resolves: bz#2155748
  (qemu crash on void blk_drain(BlockBackend *): Assertion qemu_in_main_thread() failed)
- Resolves: bz#2175660
  (Guest hangs when starting or rebooting)
This commit is contained in:
Miroslav Rezanina 2023-03-12 23:37:54 -04:00
parent cbc169813b
commit de1852f087
13 changed files with 1574 additions and 1 deletions
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50
kvm-aio-wait-switch-to-smp_mb__after_rmw.patch Normal file
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@ -0,0 +1,50 @@
From e9a9c0b023ae0dcbb14543b74063cca931d8230f Mon Sep 17 00:00:00 2001
From: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Date: Thu, 9 Mar 2023 08:24:36 -0500
Subject: [PATCH 08/12] aio-wait: switch to smp_mb__after_rmw()
RH-Author: Emanuele Giuseppe Esposito <eesposit@redhat.com>
RH-MergeRequest: 158: qatomic: add smp_mb__before/after_rmw()
RH-Bugzilla: 2175660
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
RH-Acked-by: David Hildenbrand <david@redhat.com>
RH-Acked-by: Eric Auger <eric.auger@redhat.com>
RH-Commit: [5/9] a90c96d148fdbec340a45dc6cedf3660d8be2aab (eesposit/qemu-kvm)
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2175660
commit b532526a07ef3b903ead2e055fe6cc87b41057a3
Author: Paolo Bonzini <pbonzini@redhat.com>
Date: Fri Mar 3 11:03:52 2023 +0100
aio-wait: switch to smp_mb__after_rmw()
The barrier comes after an atomic increment, so it is enough to use
smp_mb__after_rmw(); this avoids a double barrier on x86 systems.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
include/block/aio-wait.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/block/aio-wait.h b/include/block/aio-wait.h
index dd9a7f6461..da13357bb8 100644
--- a/include/block/aio-wait.h
+++ b/include/block/aio-wait.h
@@ -85,7 +85,7 @@ extern AioWait global_aio_wait;
/* Increment wait_->num_waiters before evaluating cond. */ \
qatomic_inc(&wait_->num_waiters); \
/* Paired with smp_mb in aio_wait_kick(). */ \
- smp_mb(); \
+ smp_mb__after_rmw(); \
if (ctx_ && in_aio_context_home_thread(ctx_)) { \
while ((cond)) { \
aio_poll(ctx_, true); \
--
2.39.1

66
kvm-async-clarify-usage-of-barriers-in-the-polling-case.patch Normal file
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From 3d823dda6832b76fd3d776131008107b0b0f7166 Mon Sep 17 00:00:00 2001
From: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Date: Thu, 9 Mar 2023 08:24:36 -0500
Subject: [PATCH 12/12] async: clarify usage of barriers in the polling case
RH-Author: Emanuele Giuseppe Esposito <eesposit@redhat.com>
RH-MergeRequest: 158: qatomic: add smp_mb__before/after_rmw()
RH-Bugzilla: 2175660
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
RH-Acked-by: David Hildenbrand <david@redhat.com>
RH-Acked-by: Eric Auger <eric.auger@redhat.com>
RH-Commit: [9/9] b4ea298d75a75bb61e07a27d1296e0095fbc2bbf (eesposit/qemu-kvm)
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2175660
commit 6229438cca037d42f44a96d38feb15cb102a444f
Author: Paolo Bonzini <pbonzini@redhat.com>
Date: Mon Mar 6 10:43:52 2023 +0100
async: clarify usage of barriers in the polling case
Explain that aio_context_notifier_poll() relies on
aio_notify_accept() to catch all the memory writes that were
done before ctx->notified was set to true.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
util/async.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/util/async.c b/util/async.c
index 37d3e6036d..e0846baf93 100644
--- a/util/async.c
+++ b/util/async.c
@@ -472,8 +472,9 @@ void aio_notify_accept(AioContext *ctx)
qatomic_set(&ctx->notified, false);
/*
- * Write ctx->notified before reading e.g. bh->flags. Pairs with smp_wmb
- * in aio_notify.
+ * Order reads of ctx->notified (in aio_context_notifier_poll()) and the
+ * above clearing of ctx->notified before reads of e.g. bh->flags. Pairs
+ * with smp_wmb() in aio_notify.
*/
smp_mb();
}
@@ -496,6 +497,11 @@ static bool aio_context_notifier_poll(void *opaque)
EventNotifier *e = opaque;
AioContext *ctx = container_of(e, AioContext, notifier);
+ /*
+ * No need for load-acquire because we just want to kick the
+ * event loop. aio_notify_accept() takes care of synchronizing
+ * the event loop with the producers.
+ */
return qatomic_read(&ctx->notified);
}
--
2.39.1

111
kvm-async-update-documentation-of-the-memory-barriers.patch Normal file
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@ -0,0 +1,111 @@
From 29bcf843d796ffc2a0906dea947e4cdfe9f7ec60 Mon Sep 17 00:00:00 2001
From: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Date: Thu, 9 Mar 2023 08:24:36 -0500
Subject: [PATCH 11/12] async: update documentation of the memory barriers
RH-Author: Emanuele Giuseppe Esposito <eesposit@redhat.com>
RH-MergeRequest: 158: qatomic: add smp_mb__before/after_rmw()
RH-Bugzilla: 2175660
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
RH-Acked-by: David Hildenbrand <david@redhat.com>
RH-Acked-by: Eric Auger <eric.auger@redhat.com>
RH-Commit: [8/9] 5ca20e4c8983e0bc1ecee66bead3472777abe4d1 (eesposit/qemu-kvm)
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2175660
commit 8dd48650b43dfde4ebea34191ac267e474bcc29e
Author: Paolo Bonzini <pbonzini@redhat.com>
Date: Mon Mar 6 10:15:06 2023 +0100
async: update documentation of the memory barriers
Ever since commit 8c6b0356b539 ("util/async: make bh_aio_poll() O(1)",
2020-02-22), synchronization between qemu_bh_schedule() and aio_bh_poll()
is happening when the bottom half is enqueued in the bh_list; not
when the flags are set. Update the documentation to match.
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
util/async.c | 33 +++++++++++++++++++--------------
1 file changed, 19 insertions(+), 14 deletions(-)
diff --git a/util/async.c b/util/async.c
index 63434ddae4..37d3e6036d 100644
--- a/util/async.c
+++ b/util/async.c
@@ -73,14 +73,21 @@ static void aio_bh_enqueue(QEMUBH *bh, unsigned new_flags)
unsigned old_flags;
/*
- * The memory barrier implicit in qatomic_fetch_or makes sure that:
- * 1. idle & any writes needed by the callback are done before the
- * locations are read in the aio_bh_poll.
- * 2. ctx is loaded before the callback has a chance to execute and bh
- * could be freed.
+ * Synchronizes with atomic_fetch_and() in aio_bh_dequeue(), ensuring that
+ * insertion starts after BH_PENDING is set.
*/
old_flags = qatomic_fetch_or(&bh->flags, BH_PENDING | new_flags);
+
if (!(old_flags & BH_PENDING)) {
+ /*
+ * At this point the bottom half becomes visible to aio_bh_poll().
+ * This insertion thus synchronizes with QSLIST_MOVE_ATOMIC in
+ * aio_bh_poll(), ensuring that:
+ * 1. any writes needed by the callback are visible from the callback
+ * after aio_bh_dequeue() returns bh.
+ * 2. ctx is loaded before the callback has a chance to execute and bh
+ * could be freed.
+ */
QSLIST_INSERT_HEAD_ATOMIC(&ctx->bh_list, bh, next);
}
@@ -106,11 +113,8 @@ static QEMUBH *aio_bh_dequeue(BHList *head, unsigned *flags)
QSLIST_REMOVE_HEAD(head, next);
/*
- * The qatomic_and is paired with aio_bh_enqueue(). The implicit memory
- * barrier ensures that the callback sees all writes done by the scheduling
- * thread. It also ensures that the scheduling thread sees the cleared
- * flag before bh->cb has run, and thus will call aio_notify again if
- * necessary.
+ * Synchronizes with qatomic_fetch_or() in aio_bh_enqueue(), ensuring that
+ * the removal finishes before BH_PENDING is reset.
*/
*flags = qatomic_fetch_and(&bh->flags,
~(BH_PENDING | BH_SCHEDULED | BH_IDLE));
@@ -157,6 +161,7 @@ int aio_bh_poll(AioContext *ctx)
BHListSlice *s;
int ret = 0;
+ /* Synchronizes with QSLIST_INSERT_HEAD_ATOMIC in aio_bh_enqueue(). */
QSLIST_MOVE_ATOMIC(&slice.bh_list, &ctx->bh_list);
QSIMPLEQ_INSERT_TAIL(&ctx->bh_slice_list, &slice, next);
@@ -446,15 +451,15 @@ LuringState *aio_get_linux_io_uring(AioContext *ctx)
void aio_notify(AioContext *ctx)
{
/*
- * Write e.g. bh->flags before writing ctx->notified. Pairs with smp_mb in
- * aio_notify_accept.
+ * Write e.g. ctx->bh_list before writing ctx->notified. Pairs with
+ * smp_mb() in aio_notify_accept().
*/
smp_wmb();
qatomic_set(&ctx->notified, true);
/*
- * Write ctx->notified before reading ctx->notify_me. Pairs
- * with smp_mb in aio_ctx_prepare or aio_poll.
+ * Write ctx->notified (and also ctx->bh_list) before reading ctx->notify_me.
+ * Pairs with smp_mb() in aio_ctx_prepare or aio_poll.
*/
smp_mb();
if (qatomic_read(&ctx->notify_me)) {
--
2.39.1

127
kvm-dma-helpers-prevent-dma_blk_cb-vs-dma_aio_cancel-rac.patch Normal file
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@ -0,0 +1,127 @@
From b886411a682b56bfe674f0a35d40c67c8e9dc87a Mon Sep 17 00:00:00 2001
From: Stefan Hajnoczi <stefanha@redhat.com>
Date: Tue, 21 Feb 2023 16:22:17 -0500
Subject: [PATCH 02/12] dma-helpers: prevent dma_blk_cb() vs dma_aio_cancel()
race
RH-Author: Stefan Hajnoczi <stefanha@redhat.com>
RH-MergeRequest: 155: virtio-scsi: reset SCSI devices from main loop thread
RH-Bugzilla: 2155748
RH-Acked-by: Eric Blake <eblake@redhat.com>
RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
RH-Commit: [2/3] eeeea43c25d8f4fa84591b05547fb77e4058abff (stefanha/centos-stream-qemu-kvm)
dma_blk_cb() only takes the AioContext lock around ->io_func(). That
means the rest of dma_blk_cb() is not protected. In particular, the
DMAAIOCB field accesses happen outside the lock.
There is a race when the main loop thread holds the AioContext lock and
invokes scsi_device_purge_requests() -> bdrv_aio_cancel() ->
dma_aio_cancel() while an IOThread executes dma_blk_cb(). The dbs->acb
field determines how cancellation proceeds. If dma_aio_cancel() sees
dbs->acb == NULL while dma_blk_cb() is still running, the request can be
completed twice (-ECANCELED and the actual return value).
The following assertion can occur with virtio-scsi when an IOThread is
used:
../hw/scsi/scsi-disk.c:368: scsi_dma_complete: Assertion `r->req.aiocb != NULL' failed.
Fix the race by holding the AioContext across dma_blk_cb(). Now
dma_aio_cancel() under the AioContext lock will not see
inconsistent/intermediate states.
Cc: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20230221212218.1378734-3-stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit abfcd2760b3e70727bbc0792221b8b98a733dc32)
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
hw/scsi/scsi-disk.c | 4 +---
softmmu/dma-helpers.c | 12 +++++++-----
2 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
index 5327f93f4c..b12d8b0816 100644
--- a/hw/scsi/scsi-disk.c
+++ b/hw/scsi/scsi-disk.c
@@ -354,13 +354,12 @@ done:
scsi_req_unref(&r->req);
}
+/* Called with AioContext lock held */
static void scsi_dma_complete(void *opaque, int ret)
{
SCSIDiskReq *r = (SCSIDiskReq *)opaque;
SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
- aio_context_acquire(blk_get_aio_context(s->qdev.conf.blk));
-
assert(r->req.aiocb != NULL);
r->req.aiocb = NULL;
@@ -370,7 +369,6 @@ static void scsi_dma_complete(void *opaque, int ret)
block_acct_done(blk_get_stats(s->qdev.conf.blk), &r->acct);
}
scsi_dma_complete_noio(r, ret);
- aio_context_release(blk_get_aio_context(s->qdev.conf.blk));
}
static void scsi_read_complete_noio(SCSIDiskReq *r, int ret)
diff --git a/softmmu/dma-helpers.c b/softmmu/dma-helpers.c
index 7820fec54c..2463964805 100644
--- a/softmmu/dma-helpers.c
+++ b/softmmu/dma-helpers.c
@@ -113,17 +113,19 @@ static void dma_complete(DMAAIOCB *dbs, int ret)
static void dma_blk_cb(void *opaque, int ret)
{
DMAAIOCB *dbs = (DMAAIOCB *)opaque;
+ AioContext *ctx = dbs->ctx;
dma_addr_t cur_addr, cur_len;
void *mem;
trace_dma_blk_cb(dbs, ret);
+ aio_context_acquire(ctx);
dbs->acb = NULL;
dbs->offset += dbs->iov.size;
if (dbs->sg_cur_index == dbs->sg->nsg || ret < 0) {
dma_complete(dbs, ret);
- return;
+ goto out;
}
dma_blk_unmap(dbs);
@@ -164,9 +166,9 @@ static void dma_blk_cb(void *opaque, int ret)
if (dbs->iov.size == 0) {
trace_dma_map_wait(dbs);
- dbs->bh = aio_bh_new(dbs->ctx, reschedule_dma, dbs);
+ dbs->bh = aio_bh_new(ctx, reschedule_dma, dbs);
cpu_register_map_client(dbs->bh);
- return;
+ goto out;
}
if (!QEMU_IS_ALIGNED(dbs->iov.size, dbs->align)) {
@@ -174,11 +176,11 @@ static void dma_blk_cb(void *opaque, int ret)
QEMU_ALIGN_DOWN(dbs->iov.size, dbs->align));
}
- aio_context_acquire(dbs->ctx);
dbs->acb = dbs->io_func(dbs->offset, &dbs->iov,
dma_blk_cb, dbs, dbs->io_func_opaque);
- aio_context_release(dbs->ctx);
assert(dbs->acb);
+out:
+ aio_context_release(ctx);
}
static void dma_aio_cancel(BlockAIOCB *acb)
--
2.39.1

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kvm-edu-add-smp_mb__after_rmw.patch Normal file
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@ -0,0 +1,61 @@
From 67bbeb056f75adc6c964468d876531ab68366fe0 Mon Sep 17 00:00:00 2001
From: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Date: Thu, 9 Mar 2023 08:24:36 -0500
Subject: [PATCH 07/12] edu: add smp_mb__after_rmw()
RH-Author: Emanuele Giuseppe Esposito <eesposit@redhat.com>
RH-MergeRequest: 158: qatomic: add smp_mb__before/after_rmw()
RH-Bugzilla: 2175660
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
RH-Acked-by: David Hildenbrand <david@redhat.com>
RH-Acked-by: Eric Auger <eric.auger@redhat.com>
RH-Commit: [4/9] 2ad6fd6cb33fde39d2d017d94c0dde2152ad70c4 (eesposit/qemu-kvm)
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2175660
commit 2482aeea4195ad84cf3d4e5b15b28ec5b420ed5a
Author: Paolo Bonzini <pbonzini@redhat.com>
Date: Thu Mar 2 11:16:13 2023 +0100
edu: add smp_mb__after_rmw()
Ensure ordering between clearing the COMPUTING flag and checking
IRQFACT, and between setting the IRQFACT flag and checking
COMPUTING. This ensures that no wakeups are lost.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
hw/misc/edu.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/hw/misc/edu.c b/hw/misc/edu.c
index e935c418d4..a1f8bc77e7 100644
--- a/hw/misc/edu.c
+++ b/hw/misc/edu.c
@@ -267,6 +267,8 @@ static void edu_mmio_write(void *opaque, hwaddr addr, uint64_t val,
case 0x20:
if (val & EDU_STATUS_IRQFACT) {
qatomic_or(&edu->status, EDU_STATUS_IRQFACT);
+ /* Order check of the COMPUTING flag after setting IRQFACT. */
+ smp_mb__after_rmw();
} else {
qatomic_and(&edu->status, ~EDU_STATUS_IRQFACT);
}
@@ -349,6 +351,9 @@ static void *edu_fact_thread(void *opaque)
qemu_mutex_unlock(&edu->thr_mutex);
qatomic_and(&edu->status, ~EDU_STATUS_COMPUTING);
+ /* Clear COMPUTING flag before checking IRQFACT. */
+ smp_mb__after_rmw();
+
if (qatomic_read(&edu->status) & EDU_STATUS_IRQFACT) {
qemu_mutex_lock_iothread();
edu_raise_irq(edu, FACT_IRQ);
--
2.39.1

55
kvm-physmem-add-missing-memory-barrier.patch Normal file
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@ -0,0 +1,55 @@
From 0dd4be411e35f00d006d89a15d9161f5d8783c1d Mon Sep 17 00:00:00 2001
From: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Date: Thu, 9 Mar 2023 08:24:36 -0500
Subject: [PATCH 10/12] physmem: add missing memory barrier
RH-Author: Emanuele Giuseppe Esposito <eesposit@redhat.com>
RH-MergeRequest: 158: qatomic: add smp_mb__before/after_rmw()
RH-Bugzilla: 2175660
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
RH-Acked-by: David Hildenbrand <david@redhat.com>
RH-Acked-by: Eric Auger <eric.auger@redhat.com>
RH-Commit: [7/9] ee4875cb8c564f0510e48b00a5d95c0e6ea6301b (eesposit/qemu-kvm)
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2175660
commit 33828ca11da08436e1b32f3e79dabce3061a0427
Author: Paolo Bonzini <pbonzini@redhat.com>
Date: Fri Mar 3 14:36:32 2023 +0100
physmem: add missing memory barrier
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
softmmu/physmem.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index 1b606a3002..772c9896cd 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -3117,6 +3117,8 @@ void cpu_register_map_client(QEMUBH *bh)
qemu_mutex_lock(&map_client_list_lock);
client->bh = bh;
QLIST_INSERT_HEAD(&map_client_list, client, link);
+ /* Write map_client_list before reading in_use. */
+ smp_mb();
if (!qatomic_read(&bounce.in_use)) {
cpu_notify_map_clients_locked();
}
@@ -3309,6 +3311,7 @@ void address_space_unmap(AddressSpace *as, void *buffer, hwaddr len,
qemu_vfree(bounce.buffer);
bounce.buffer = NULL;
memory_region_unref(bounce.mr);
+ /* Clear in_use before reading map_client_list. */
qatomic_mb_set(&bounce.in_use, false);
cpu_notify_map_clients();
}
--
2.39.1

177
kvm-qatomic-add-smp_mb__before-after_rmw.patch Normal file
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@ -0,0 +1,177 @@
From 1fdc864f9ac927f3ea407f35f6771a4b2e8f509f Mon Sep 17 00:00:00 2001
From: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Date: Thu, 9 Mar 2023 08:24:36 -0500
Subject: [PATCH 04/12] qatomic: add smp_mb__before/after_rmw()
RH-Author: Emanuele Giuseppe Esposito <eesposit@redhat.com>
RH-MergeRequest: 158: qatomic: add smp_mb__before/after_rmw()
RH-Bugzilla: 2175660
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
RH-Acked-by: David Hildenbrand <david@redhat.com>
RH-Acked-by: Eric Auger <eric.auger@redhat.com>
RH-Commit: [1/9] e8d0b64670bff778d275b1fb477dcee0c109251a (eesposit/qemu-kvm)
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2175660
commit ff00bed1897c3d27adc5b0cec6f6eeb5a7d13176
Author: Paolo Bonzini <pbonzini@redhat.com>
Date: Thu Mar 2 11:10:56 2023 +0100
qatomic: add smp_mb__before/after_rmw()
On ARM, seqcst loads and stores (which QEMU does not use) are compiled
respectively as LDAR and STLR instructions. Even though LDAR is
also used for load-acquire operations, it also waits for all STLRs to
leave the store buffer. Thus, LDAR and STLR alone are load-acquire
and store-release operations, but LDAR also provides store-against-load
ordering as long as the previous store is a STLR.
Compare this to ARMv7, where store-release is DMB+STR and load-acquire
is LDR+DMB, but an additional DMB is needed between store-seqcst and
load-seqcst (e.g. DMB+STR+DMB+LDR+DMB); or with x86, where MOV provides
load-acquire and store-release semantics and the two can be reordered.
Likewise, on ARM sequentially consistent read-modify-write operations only
need to use LDAXR and STLXR respectively for the load and the store, while
on x86 they need to use the stronger LOCK prefix.
In a strange twist of events, however, the _stronger_ semantics
of the ARM instructions can end up causing bugs on ARM, not on x86.
The problems occur when seqcst atomics are mixed with relaxed atomics.
QEMU's atomics try to bridge the Linux API (that most of the developers
are familiar with) and the C11 API, and the two have a substantial
difference:
- in Linux, strongly-ordered atomics such as atomic_add_return() affect
the global ordering of _all_ memory operations, including for example
READ_ONCE()/WRITE_ONCE()
- in C11, sequentially consistent atomics (except for seq-cst fences)
only affect the ordering of sequentially consistent operations.
In particular, since relaxed loads are done with LDR on ARM, they are
not ordered against seqcst stores (which are done with STLR).
QEMU implements high-level synchronization primitives with the idea that
the primitives contain the necessary memory barriers, and the callers can
use relaxed atomics (qatomic_read/qatomic_set) or even regular accesses.
This is very much incompatible with the C11 view that seqcst accesses
are only ordered against other seqcst accesses, and requires using seqcst
fences as in the following example:
qatomic_set(&y, 1); qatomic_set(&x, 1);
smp_mb(); smp_mb();
... qatomic_read(&x) ... ... qatomic_read(&y) ...
When a qatomic_*() read-modify write operation is used instead of one
or both stores, developers that are more familiar with the Linux API may
be tempted to omit the smp_mb(), which will work on x86 but not on ARM.
This nasty difference between Linux and C11 read-modify-write operations
has already caused issues in util/async.c and more are being found.
Provide something similar to Linux smp_mb__before/after_atomic(); this
has the double function of documenting clearly why there is a memory
barrier, and avoiding a double barrier on x86 and s390x systems.
The new macro can already be put to use in qatomic_mb_set().
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
docs/devel/atomics.rst | 26 +++++++++++++++++++++-----
include/qemu/atomic.h | 17 ++++++++++++++++-
2 files changed, 37 insertions(+), 6 deletions(-)
diff --git a/docs/devel/atomics.rst b/docs/devel/atomics.rst
index 52baa0736d..10fbfc58bb 100644
--- a/docs/devel/atomics.rst
+++ b/docs/devel/atomics.rst
@@ -25,7 +25,8 @@ provides macros that fall in three camps:
- weak atomic access and manual memory barriers: ``qatomic_read()``,
``qatomic_set()``, ``smp_rmb()``, ``smp_wmb()``, ``smp_mb()``,
- ``smp_mb_acquire()``, ``smp_mb_release()``, ``smp_read_barrier_depends()``;
+ ``smp_mb_acquire()``, ``smp_mb_release()``, ``smp_read_barrier_depends()``,
+ ``smp_mb__before_rmw()``, ``smp_mb__after_rmw()``;
- sequentially consistent atomic access: everything else.
@@ -470,7 +471,7 @@ and memory barriers, and the equivalents in QEMU:
sequential consistency.
- in QEMU, ``qatomic_read()`` and ``qatomic_set()`` do not participate in
- the total ordering enforced by sequentially-consistent operations.
+ the ordering enforced by read-modify-write operations.
This is because QEMU uses the C11 memory model. The following example
is correct in Linux but not in QEMU:
@@ -486,9 +487,24 @@ and memory barriers, and the equivalents in QEMU:
because the read of ``y`` can be moved (by either the processor or the
compiler) before the write of ``x``.
- Fixing this requires an ``smp_mb()`` memory barrier between the write
- of ``x`` and the read of ``y``. In the common case where only one thread
- writes ``x``, it is also possible to write it like this:
+ Fixing this requires a full memory barrier between the write of ``x`` and
+ the read of ``y``. QEMU provides ``smp_mb__before_rmw()`` and
+ ``smp_mb__after_rmw()``; they act both as an optimization,
+ avoiding the memory barrier on processors where it is unnecessary,
+ and as a clarification of this corner case of the C11 memory model:
+
+ +--------------------------------+
+ | QEMU (correct) |
+ +================================+
+ | :: |
+ | |
+ | a = qatomic_fetch_add(&x, 2);|
+ | smp_mb__after_rmw(); |
+ | b = qatomic_read(&y); |
+ +--------------------------------+
+
+ In the common case where only one thread writes ``x``, it is also possible
+ to write it like this:
+--------------------------------+
| QEMU (correct) |
diff --git a/include/qemu/atomic.h b/include/qemu/atomic.h
index 874134fd19..f85834ee8b 100644
--- a/include/qemu/atomic.h
+++ b/include/qemu/atomic.h
@@ -245,6 +245,20 @@
#define smp_wmb() smp_mb_release()
#define smp_rmb() smp_mb_acquire()
+/*
+ * SEQ_CST is weaker than the older __sync_* builtins and Linux
+ * kernel read-modify-write atomics. Provide a macro to obtain
+ * the same semantics.
+ */
+#if !defined(QEMU_SANITIZE_THREAD) && \
+ (defined(__i386__) || defined(__x86_64__) || defined(__s390x__))
+# define smp_mb__before_rmw() signal_barrier()
+# define smp_mb__after_rmw() signal_barrier()
+#else
+# define smp_mb__before_rmw() smp_mb()
+# define smp_mb__after_rmw() smp_mb()
+#endif
+
/* qatomic_mb_read/set semantics map Java volatile variables. They are
* less expensive on some platforms (notably POWER) than fully
* sequentially consistent operations.
@@ -259,7 +273,8 @@
#if !defined(QEMU_SANITIZE_THREAD) && \
(defined(__i386__) || defined(__x86_64__) || defined(__s390x__))
/* This is more efficient than a store plus a fence. */
-# define qatomic_mb_set(ptr, i) ((void)qatomic_xchg(ptr, i))
+# define qatomic_mb_set(ptr, i) \
+ ({ (void)qatomic_xchg(ptr, i); smp_mb__after_rmw(); })
#else
# define qatomic_mb_set(ptr, i) \
({ qatomic_store_release(ptr, i); smp_mb(); })
--
2.39.1

75
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@ -0,0 +1,75 @@
From 7a9907c65e3e2bbb0c119acdbbeb4381e7f1d902 Mon Sep 17 00:00:00 2001
From: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Date: Thu, 9 Mar 2023 08:24:36 -0500
Subject: [PATCH 09/12] qemu-coroutine-lock: add smp_mb__after_rmw()
RH-Author: Emanuele Giuseppe Esposito <eesposit@redhat.com>
RH-MergeRequest: 158: qatomic: add smp_mb__before/after_rmw()
RH-Bugzilla: 2175660
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
RH-Acked-by: David Hildenbrand <david@redhat.com>
RH-Acked-by: Eric Auger <eric.auger@redhat.com>
RH-Commit: [6/9] 4b1723b1ad670ec4c85240390b4fc15ff361154f (eesposit/qemu-kvm)
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2175660
commit e3a3b6ec8169eab2feb241b4982585001512cd55
Author: Paolo Bonzini <pbonzini@redhat.com>
Date: Fri Mar 3 10:52:59 2023 +0100
qemu-coroutine-lock: add smp_mb__after_rmw()
mutex->from_push and mutex->handoff in qemu-coroutine-lock implement
the familiar pattern:
write a write b
smp_mb() smp_mb()
read b read a
The memory barrier is required by the C memory model even after a
SEQ_CST read-modify-write operation such as QSLIST_INSERT_HEAD_ATOMIC.
Add it and avoid the unclear qatomic_mb_read() operation.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
util/qemu-coroutine-lock.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/util/qemu-coroutine-lock.c b/util/qemu-coroutine-lock.c
index 45c6b57374..c5897bd963 100644
--- a/util/qemu-coroutine-lock.c
+++ b/util/qemu-coroutine-lock.c
@@ -202,10 +202,16 @@ static void coroutine_fn qemu_co_mutex_lock_slowpath(AioContext *ctx,
trace_qemu_co_mutex_lock_entry(mutex, self);
push_waiter(mutex, &w);
+ /*
+ * Add waiter before reading mutex->handoff. Pairs with qatomic_mb_set
+ * in qemu_co_mutex_unlock.
+ */
+ smp_mb__after_rmw();
+
/* This is the "Responsibility Hand-Off" protocol; a lock() picks from
* a concurrent unlock() the responsibility of waking somebody up.
*/
- old_handoff = qatomic_mb_read(&mutex->handoff);
+ old_handoff = qatomic_read(&mutex->handoff);
if (old_handoff &&
has_waiters(mutex) &&
qatomic_cmpxchg(&mutex->handoff, old_handoff, 0) == old_handoff) {
@@ -304,6 +310,7 @@ void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex)
}
our_handoff = mutex->sequence;
+ /* Set handoff before checking for waiters. */
qatomic_mb_set(&mutex->handoff, our_handoff);
if (!has_waiters(mutex)) {
/* The concurrent lock has not added itself yet, so it
--
2.39.1

146
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@ -0,0 +1,146 @@
From aa61e4c437d29a791ea09a01f7230231f1e53356 Mon Sep 17 00:00:00 2001
From: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Date: Thu, 9 Mar 2023 08:24:36 -0500
Subject: [PATCH 05/12] qemu-thread-posix: cleanup, fix, document QemuEvent
RH-Author: Emanuele Giuseppe Esposito <eesposit@redhat.com>
RH-MergeRequest: 158: qatomic: add smp_mb__before/after_rmw()
RH-Bugzilla: 2175660
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
RH-Acked-by: David Hildenbrand <david@redhat.com>
RH-Acked-by: Eric Auger <eric.auger@redhat.com>
RH-Commit: [2/9] c3bdf75f884e137c667316aaac96bb4a0b9ec2d9 (eesposit/qemu-kvm)
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2175660
commit 9586a1329f5dce6c1d7f4de53cf0536644d7e593
Author: Paolo Bonzini <pbonzini@redhat.com>
Date: Thu Mar 2 11:19:52 2023 +0100
qemu-thread-posix: cleanup, fix, document QemuEvent
QemuEvent is currently broken on ARM due to missing memory barriers
after qatomic_*(). Apart from adding the memory barrier, a closer look
reveals some unpaired memory barriers too. Document more clearly what
is going on.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
util/qemu-thread-posix.c | 69 ++++++++++++++++++++++++++++------------
1 file changed, 49 insertions(+), 20 deletions(-)
diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
index bae938c670..cc74f4ede0 100644
--- a/util/qemu-thread-posix.c
+++ b/util/qemu-thread-posix.c
@@ -379,13 +379,21 @@ void qemu_event_destroy(QemuEvent *ev)
void qemu_event_set(QemuEvent *ev)
{
- /* qemu_event_set has release semantics, but because it *loads*
+ assert(ev->initialized);
+
+ /*
+ * Pairs with both qemu_event_reset() and qemu_event_wait().
+ *
+ * qemu_event_set has release semantics, but because it *loads*
* ev->value we need a full memory barrier here.
*/
- assert(ev->initialized);
smp_mb();
if (qatomic_read(&ev->value) != EV_SET) {
- if (qatomic_xchg(&ev->value, EV_SET) == EV_BUSY) {
+ int old = qatomic_xchg(&ev->value, EV_SET);
+
+ /* Pairs with memory barrier in kernel futex_wait system call. */
+ smp_mb__after_rmw();
+ if (old == EV_BUSY) {
/* There were waiters, wake them up. */
qemu_futex_wake(ev, INT_MAX);
}
@@ -394,18 +402,19 @@ void qemu_event_set(QemuEvent *ev)
void qemu_event_reset(QemuEvent *ev)
{
- unsigned value;
-
assert(ev->initialized);
- value = qatomic_read(&ev->value);
- smp_mb_acquire();
- if (value == EV_SET) {
- /*
- * If there was a concurrent reset (or even reset+wait),
- * do nothing. Otherwise change EV_SET->EV_FREE.
- */
- qatomic_or(&ev->value, EV_FREE);
- }
+
+ /*
+ * If there was a concurrent reset (or even reset+wait),
+ * do nothing. Otherwise change EV_SET->EV_FREE.
+ */
+ qatomic_or(&ev->value, EV_FREE);
+
+ /*
+ * Order reset before checking the condition in the caller.
+ * Pairs with the first memory barrier in qemu_event_set().
+ */
+ smp_mb__after_rmw();
}
void qemu_event_wait(QemuEvent *ev)
@@ -413,20 +422,40 @@ void qemu_event_wait(QemuEvent *ev)
unsigned value;
assert(ev->initialized);
- value = qatomic_read(&ev->value);
- smp_mb_acquire();
+
+ /*
+ * qemu_event_wait must synchronize with qemu_event_set even if it does
+ * not go down the slow path, so this load-acquire is needed that
+ * synchronizes with the first memory barrier in qemu_event_set().
+ *
+ * If we do go down the slow path, there is no requirement at all: we
+ * might miss a qemu_event_set() here but ultimately the memory barrier in
+ * qemu_futex_wait() will ensure the check is done correctly.
+ */
+ value = qatomic_load_acquire(&ev->value);
if (value != EV_SET) {
if (value == EV_FREE) {
/*
- * Leave the event reset and tell qemu_event_set that there
- * are waiters. No need to retry, because there cannot be
- * a concurrent busy->free transition. After the CAS, the
- * event will be either set or busy.
+ * Leave the event reset and tell qemu_event_set that there are
+ * waiters. No need to retry, because there cannot be a concurrent
+ * busy->free transition. After the CAS, the event will be either
+ * set or busy.
+ *
+ * This cmpxchg doesn't have particular ordering requirements if it
+ * succeeds (moving the store earlier can only cause qemu_event_set()
+ * to issue _more_ wakeups), the failing case needs acquire semantics
+ * like the load above.
*/
if (qatomic_cmpxchg(&ev->value, EV_FREE, EV_BUSY) == EV_SET) {
return;
}
}
+
+ /*
+ * This is the final check for a concurrent set, so it does need
+ * a smp_mb() pairing with the second barrier of qemu_event_set().
+ * The barrier is inside the FUTEX_WAIT system call.
+ */
qemu_futex_wait(ev, EV_BUSY);
}
}
--
2.39.1

162
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@ -0,0 +1,162 @@
From 02347869410fe53d814487501fb586f7dc614375 Mon Sep 17 00:00:00 2001
From: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Date: Thu, 9 Mar 2023 08:24:36 -0500
Subject: [PATCH 06/12] qemu-thread-win32: cleanup, fix, document QemuEvent
RH-Author: Emanuele Giuseppe Esposito <eesposit@redhat.com>
RH-MergeRequest: 158: qatomic: add smp_mb__before/after_rmw()
RH-Bugzilla: 2175660
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
RH-Acked-by: David Hildenbrand <david@redhat.com>
RH-Acked-by: Eric Auger <eric.auger@redhat.com>
RH-Commit: [3/9] d228e9d6a4a75dd1f0a23a6dceaf4fea23d69192 (eesposit/qemu-kvm)
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2175660
commit 6c5df4b48f0c52a61342ecb307a43f4c2a3565c4
Author: Paolo Bonzini <pbonzini@redhat.com>
Date: Thu Mar 2 11:22:50 2023 +0100
qemu-thread-win32: cleanup, fix, document QemuEvent
QemuEvent is currently broken on ARM due to missing memory barriers
after qatomic_*(). Apart from adding the memory barrier, a closer look
reveals some unpaired memory barriers that are not really needed and
complicated the functions unnecessarily. Also, it is relying on
a memory barrier in ResetEvent(); the barrier _ought_ to be there
but there is really no documentation about it, so make it explicit.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
util/qemu-thread-win32.c | 82 +++++++++++++++++++++++++++-------------
1 file changed, 56 insertions(+), 26 deletions(-)
diff --git a/util/qemu-thread-win32.c b/util/qemu-thread-win32.c
index 69db254ac7..a7fe3cc345 100644
--- a/util/qemu-thread-win32.c
+++ b/util/qemu-thread-win32.c
@@ -272,12 +272,20 @@ void qemu_event_destroy(QemuEvent *ev)
void qemu_event_set(QemuEvent *ev)
{
assert(ev->initialized);
- /* qemu_event_set has release semantics, but because it *loads*
+
+ /*
+ * Pairs with both qemu_event_reset() and qemu_event_wait().
+ *
+ * qemu_event_set has release semantics, but because it *loads*
* ev->value we need a full memory barrier here.
*/
smp_mb();
if (qatomic_read(&ev->value) != EV_SET) {
- if (qatomic_xchg(&ev->value, EV_SET) == EV_BUSY) {
+ int old = qatomic_xchg(&ev->value, EV_SET);
+
+ /* Pairs with memory barrier after ResetEvent. */
+ smp_mb__after_rmw();
+ if (old == EV_BUSY) {
/* There were waiters, wake them up. */
SetEvent(ev->event);
}
@@ -286,17 +294,19 @@ void qemu_event_set(QemuEvent *ev)
void qemu_event_reset(QemuEvent *ev)
{
- unsigned value;
-
assert(ev->initialized);
- value = qatomic_read(&ev->value);
- smp_mb_acquire();
- if (value == EV_SET) {
- /* If there was a concurrent reset (or even reset+wait),
- * do nothing. Otherwise change EV_SET->EV_FREE.
- */
- qatomic_or(&ev->value, EV_FREE);
- }
+
+ /*
+ * If there was a concurrent reset (or even reset+wait),
+ * do nothing. Otherwise change EV_SET->EV_FREE.
+ */
+ qatomic_or(&ev->value, EV_FREE);
+
+ /*
+ * Order reset before checking the condition in the caller.
+ * Pairs with the first memory barrier in qemu_event_set().
+ */
+ smp_mb__after_rmw();
}
void qemu_event_wait(QemuEvent *ev)
@@ -304,29 +314,49 @@ void qemu_event_wait(QemuEvent *ev)
unsigned value;
assert(ev->initialized);
- value = qatomic_read(&ev->value);
- smp_mb_acquire();
+
+ /*
+ * qemu_event_wait must synchronize with qemu_event_set even if it does
+ * not go down the slow path, so this load-acquire is needed that
+ * synchronizes with the first memory barrier in qemu_event_set().
+ *
+ * If we do go down the slow path, there is no requirement at all: we
+ * might miss a qemu_event_set() here but ultimately the memory barrier in
+ * qemu_futex_wait() will ensure the check is done correctly.
+ */
+ value = qatomic_load_acquire(&ev->value);
if (value != EV_SET) {
if (value == EV_FREE) {
- /* qemu_event_set is not yet going to call SetEvent, but we are
- * going to do another check for EV_SET below when setting EV_BUSY.
- * At that point it is safe to call WaitForSingleObject.
+ /*
+ * Here the underlying kernel event is reset, but qemu_event_set is
+ * not yet going to call SetEvent. However, there will be another
+ * check for EV_SET below when setting EV_BUSY. At that point it
+ * is safe to call WaitForSingleObject.
*/
ResetEvent(ev->event);
- /* Tell qemu_event_set that there are waiters. No need to retry
- * because there cannot be a concurrent busy->free transition.
- * After the CAS, the event will be either set or busy.
+ /*
+ * It is not clear whether ResetEvent provides this barrier; kernel
+ * APIs (KeResetEvent/KeClearEvent) do not. Better safe than sorry!
+ */
+ smp_mb();
+
+ /*
+ * Leave the event reset and tell qemu_event_set that there are
+ * waiters. No need to retry, because there cannot be a concurrent
+ * busy->free transition. After the CAS, the event will be either
+ * set or busy.
*/
if (qatomic_cmpxchg(&ev->value, EV_FREE, EV_BUSY) == EV_SET) {
- value = EV_SET;
- } else {
- value = EV_BUSY;
+ return;
}
}
- if (value == EV_BUSY) {
- WaitForSingleObject(ev->event, INFINITE);
- }
+
+ /*
+ * ev->value is now EV_BUSY. Since we didn't observe EV_SET,
+ * qemu_event_set() must observe EV_BUSY and call SetEvent().
+ */
+ WaitForSingleObject(ev->event, INFINITE);
}
}
--
2.39.1

176
kvm-scsi-protect-req-aiocb-with-AioContext-lock.patch Normal file
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@ -0,0 +1,176 @@
From 0a4f5bcc2a6f8ac31431e971c1dce9e6ab2191c2 Mon Sep 17 00:00:00 2001
From: Stefan Hajnoczi <stefanha@redhat.com>
Date: Tue, 21 Feb 2023 16:22:16 -0500
Subject: [PATCH 01/12] scsi: protect req->aiocb with AioContext lock
RH-Author: Stefan Hajnoczi <stefanha@redhat.com>
RH-MergeRequest: 155: virtio-scsi: reset SCSI devices from main loop thread
RH-Bugzilla: 2155748
RH-Acked-by: Eric Blake <eblake@redhat.com>
RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
RH-Commit: [1/3] 61727297bd31dfe18220b61f1d265ced0649c60d (stefanha/centos-stream-qemu-kvm)
If requests are being processed in the IOThread when a SCSIDevice is
unplugged, scsi_device_purge_requests() -> scsi_req_cancel_async() races
with I/O completion callbacks. Both threads load and store req->aiocb.
This can lead to assert(r->req.aiocb == NULL) failures and undefined
behavior.
Protect r->req.aiocb with the AioContext lock to prevent the race.
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20230221212218.1378734-2-stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 7b7fc3d0102dafe8eb44802493036a526e921a71)
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
hw/scsi/scsi-disk.c | 23 ++++++++++++++++-------
hw/scsi/scsi-generic.c | 11 ++++++-----
2 files changed, 22 insertions(+), 12 deletions(-)
diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
index e493c28814..5327f93f4c 100644
--- a/hw/scsi/scsi-disk.c
+++ b/hw/scsi/scsi-disk.c
@@ -273,9 +273,11 @@ static void scsi_aio_complete(void *opaque, int ret)
SCSIDiskReq *r = (SCSIDiskReq *)opaque;
SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
+ aio_context_acquire(blk_get_aio_context(s->qdev.conf.blk));
+
assert(r->req.aiocb != NULL);
r->req.aiocb = NULL;
- aio_context_acquire(blk_get_aio_context(s->qdev.conf.blk));
+
if (scsi_disk_req_check_error(r, ret, true)) {
goto done;
}
@@ -357,10 +359,11 @@ static void scsi_dma_complete(void *opaque, int ret)
SCSIDiskReq *r = (SCSIDiskReq *)opaque;
SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
+ aio_context_acquire(blk_get_aio_context(s->qdev.conf.blk));
+
assert(r->req.aiocb != NULL);
r->req.aiocb = NULL;
- aio_context_acquire(blk_get_aio_context(s->qdev.conf.blk));
if (ret < 0) {
block_acct_failed(blk_get_stats(s->qdev.conf.blk), &r->acct);
} else {
@@ -393,10 +396,11 @@ static void scsi_read_complete(void *opaque, int ret)
SCSIDiskReq *r = (SCSIDiskReq *)opaque;
SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
+ aio_context_acquire(blk_get_aio_context(s->qdev.conf.blk));
+
assert(r->req.aiocb != NULL);
r->req.aiocb = NULL;
- aio_context_acquire(blk_get_aio_context(s->qdev.conf.blk));
if (ret < 0) {
block_acct_failed(blk_get_stats(s->qdev.conf.blk), &r->acct);
} else {
@@ -446,10 +450,11 @@ static void scsi_do_read_cb(void *opaque, int ret)
SCSIDiskReq *r = (SCSIDiskReq *)opaque;
SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
+ aio_context_acquire(blk_get_aio_context(s->qdev.conf.blk));
+
assert (r->req.aiocb != NULL);
r->req.aiocb = NULL;
- aio_context_acquire(blk_get_aio_context(s->qdev.conf.blk));
if (ret < 0) {
block_acct_failed(blk_get_stats(s->qdev.conf.blk), &r->acct);
} else {
@@ -530,10 +535,11 @@ static void scsi_write_complete(void * opaque, int ret)
SCSIDiskReq *r = (SCSIDiskReq *)opaque;
SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
+ aio_context_acquire(blk_get_aio_context(s->qdev.conf.blk));
+
assert (r->req.aiocb != NULL);
r->req.aiocb = NULL;
- aio_context_acquire(blk_get_aio_context(s->qdev.conf.blk));
if (ret < 0) {
block_acct_failed(blk_get_stats(s->qdev.conf.blk), &r->acct);
} else {
@@ -1737,10 +1743,11 @@ static void scsi_unmap_complete(void *opaque, int ret)
SCSIDiskReq *r = data->r;
SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
+ aio_context_acquire(blk_get_aio_context(s->qdev.conf.blk));
+
assert(r->req.aiocb != NULL);
r->req.aiocb = NULL;
- aio_context_acquire(blk_get_aio_context(s->qdev.conf.blk));
if (scsi_disk_req_check_error(r, ret, true)) {
scsi_req_unref(&r->req);
g_free(data);
@@ -1816,9 +1823,11 @@ static void scsi_write_same_complete(void *opaque, int ret)
SCSIDiskReq *r = data->r;
SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
+ aio_context_acquire(blk_get_aio_context(s->qdev.conf.blk));
+
assert(r->req.aiocb != NULL);
r->req.aiocb = NULL;
- aio_context_acquire(blk_get_aio_context(s->qdev.conf.blk));
+
if (scsi_disk_req_check_error(r, ret, true)) {
goto done;
}
diff --git a/hw/scsi/scsi-generic.c b/hw/scsi/scsi-generic.c
index 92cce20a4d..ac9fa662b4 100644
--- a/hw/scsi/scsi-generic.c
+++ b/hw/scsi/scsi-generic.c
@@ -111,10 +111,11 @@ static void scsi_command_complete(void *opaque, int ret)
SCSIGenericReq *r = (SCSIGenericReq *)opaque;
SCSIDevice *s = r->req.dev;
+ aio_context_acquire(blk_get_aio_context(s->conf.blk));
+
assert(r->req.aiocb != NULL);
r->req.aiocb = NULL;
- aio_context_acquire(blk_get_aio_context(s->conf.blk));
scsi_command_complete_noio(r, ret);
aio_context_release(blk_get_aio_context(s->conf.blk));
}
@@ -269,11 +270,11 @@ static void scsi_read_complete(void * opaque, int ret)
SCSIDevice *s = r->req.dev;
int len;
+ aio_context_acquire(blk_get_aio_context(s->conf.blk));
+
assert(r->req.aiocb != NULL);
r->req.aiocb = NULL;
- aio_context_acquire(blk_get_aio_context(s->conf.blk));
-
if (ret || r->req.io_canceled) {
scsi_command_complete_noio(r, ret);
goto done;
@@ -386,11 +387,11 @@ static void scsi_write_complete(void * opaque, int ret)
trace_scsi_generic_write_complete(ret);
+ aio_context_acquire(blk_get_aio_context(s->conf.blk));
+
assert(r->req.aiocb != NULL);
r->req.aiocb = NULL;
- aio_context_acquire(blk_get_aio_context(s->conf.blk));
-
if (ret || r->req.io_canceled) {
scsi_command_complete_noio(r, ret);
goto done;
--
2.39.1

325
kvm-virtio-scsi-reset-SCSI-devices-from-main-loop-thread.patch Normal file
View File

@ -0,0 +1,325 @@
From c64027b1ff9856031c01009f4b5c3560d92cc998 Mon Sep 17 00:00:00 2001
From: Stefan Hajnoczi <stefanha@redhat.com>
Date: Tue, 21 Feb 2023 16:22:18 -0500
Subject: [PATCH 03/12] virtio-scsi: reset SCSI devices from main loop thread
RH-Author: Stefan Hajnoczi <stefanha@redhat.com>
RH-MergeRequest: 155: virtio-scsi: reset SCSI devices from main loop thread
RH-Bugzilla: 2155748
RH-Acked-by: Eric Blake <eblake@redhat.com>
RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
RH-Commit: [3/3] 2a29cb9600709a799daadb4addb58a747ed2e3a3 (stefanha/centos-stream-qemu-kvm)
When an IOThread is configured, the ctrl virtqueue is processed in the
IOThread. TMFs that reset SCSI devices are currently called directly
from the IOThread and trigger an assertion failure in blk_drain() from
the following call stack:
virtio_scsi_handle_ctrl_req -> virtio_scsi_do_tmf -> device_code_reset
-> scsi_disk_reset -> scsi_device_purge_requests -> blk_drain
../block/block-backend.c:1780: void blk_drain(BlockBackend *): Assertion `qemu_in_main_thread()' failed.
The blk_drain() function is not designed to be called from an IOThread
because it needs the Big QEMU Lock (BQL).
This patch defers TMFs that reset SCSI devices to a Bottom Half (BH)
that runs in the main loop thread under the BQL. This way it's safe to
call blk_drain() and the assertion failure is avoided.
Introduce s->tmf_bh_list for tracking TMF requests that have been
deferred to the BH. When the BH runs it will grab the entire list and
process all requests. Care must be taken to clear the list when the
virtio-scsi device is reset or unrealized. Otherwise deferred TMF
requests could execute later and lead to use-after-free or other
undefined behavior.
The s->resetting counter that's used by TMFs that reset SCSI devices is
accessed from multiple threads. This patch makes that explicit by using
atomic accessor functions. With this patch applied the counter is only
modified by the main loop thread under the BQL but can be read by any
thread.
Reported-by: Qing Wang <qinwang@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20230221212218.1378734-4-stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit be2c42b97c3a3a395b2f05bad1b6c7de20ecf2a5)
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
hw/scsi/virtio-scsi.c | 169 +++++++++++++++++++++++++-------
include/hw/virtio/virtio-scsi.h | 11 ++-
2 files changed, 143 insertions(+), 37 deletions(-)
diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
index 6f6e2e32ba..7d27e4c2a1 100644
--- a/hw/scsi/virtio-scsi.c
+++ b/hw/scsi/virtio-scsi.c
@@ -42,13 +42,11 @@ typedef struct VirtIOSCSIReq {
QEMUSGList qsgl;
QEMUIOVector resp_iov;
- union {
- /* Used for two-stage request submission */
- QTAILQ_ENTRY(VirtIOSCSIReq) next;
+ /* Used for two-stage request submission and TMFs deferred to BH */
+ QTAILQ_ENTRY(VirtIOSCSIReq) next;
- /* Used for cancellation of request during TMFs */
- int remaining;
- };
+ /* Used for cancellation of request during TMFs */
+ int remaining;
SCSIRequest *sreq;
size_t resp_size;
@@ -293,6 +291,122 @@ static inline void virtio_scsi_ctx_check(VirtIOSCSI *s, SCSIDevice *d)
}
}
+static void virtio_scsi_do_one_tmf_bh(VirtIOSCSIReq *req)
+{
+ VirtIOSCSI *s = req->dev;
+ SCSIDevice *d = virtio_scsi_device_get(s, req->req.tmf.lun);
+ BusChild *kid;
+ int target;
+
+ switch (req->req.tmf.subtype) {
+ case VIRTIO_SCSI_T_TMF_LOGICAL_UNIT_RESET:
+ if (!d) {
+ req->resp.tmf.response = VIRTIO_SCSI_S_BAD_TARGET;
+ goto out;
+ }
+ if (d->lun != virtio_scsi_get_lun(req->req.tmf.lun)) {
+ req->resp.tmf.response = VIRTIO_SCSI_S_INCORRECT_LUN;
+ goto out;
+ }
+ qatomic_inc(&s->resetting);
+ device_cold_reset(&d->qdev);
+ qatomic_dec(&s->resetting);
+ break;
+
+ case VIRTIO_SCSI_T_TMF_I_T_NEXUS_RESET:
+ target = req->req.tmf.lun[1];
+ qatomic_inc(&s->resetting);
+
+ rcu_read_lock();
+ QTAILQ_FOREACH_RCU(kid, &s->bus.qbus.children, sibling) {
+ SCSIDevice *d1 = SCSI_DEVICE(kid->child);
+ if (d1->channel == 0 && d1->id == target) {
+ device_cold_reset(&d1->qdev);
+ }
+ }
+ rcu_read_unlock();
+
+ qatomic_dec(&s->resetting);
+ break;
+
+ default:
+ g_assert_not_reached();
+ break;
+ }
+
+out:
+ object_unref(OBJECT(d));
+
+ virtio_scsi_acquire(s);
+ virtio_scsi_complete_req(req);
+ virtio_scsi_release(s);
+}
+
+/* Some TMFs must be processed from the main loop thread */
+static void virtio_scsi_do_tmf_bh(void *opaque)
+{
+ VirtIOSCSI *s = opaque;
+ QTAILQ_HEAD(, VirtIOSCSIReq) reqs = QTAILQ_HEAD_INITIALIZER(reqs);
+ VirtIOSCSIReq *req;
+ VirtIOSCSIReq *tmp;
+
+ GLOBAL_STATE_CODE();
+
+ virtio_scsi_acquire(s);
+
+ QTAILQ_FOREACH_SAFE(req, &s->tmf_bh_list, next, tmp) {
+ QTAILQ_REMOVE(&s->tmf_bh_list, req, next);
+ QTAILQ_INSERT_TAIL(&reqs, req, next);
+ }
+
+ qemu_bh_delete(s->tmf_bh);
+ s->tmf_bh = NULL;
+
+ virtio_scsi_release(s);
+
+ QTAILQ_FOREACH_SAFE(req, &reqs, next, tmp) {
+ QTAILQ_REMOVE(&reqs, req, next);
+ virtio_scsi_do_one_tmf_bh(req);
+ }
+}
+
+static void virtio_scsi_reset_tmf_bh(VirtIOSCSI *s)
+{
+ VirtIOSCSIReq *req;
+ VirtIOSCSIReq *tmp;
+
+ GLOBAL_STATE_CODE();
+
+ virtio_scsi_acquire(s);
+
+ if (s->tmf_bh) {
+ qemu_bh_delete(s->tmf_bh);
+ s->tmf_bh = NULL;
+ }
+
+ QTAILQ_FOREACH_SAFE(req, &s->tmf_bh_list, next, tmp) {
+ QTAILQ_REMOVE(&s->tmf_bh_list, req, next);
+
+ /* SAM-6 6.3.2 Hard reset */
+ req->resp.tmf.response = VIRTIO_SCSI_S_TARGET_FAILURE;
+ virtio_scsi_complete_req(req);
+ }
+
+ virtio_scsi_release(s);
+}
+
+static void virtio_scsi_defer_tmf_to_bh(VirtIOSCSIReq *req)
+{
+ VirtIOSCSI *s = req->dev;
+
+ QTAILQ_INSERT_TAIL(&s->tmf_bh_list, req, next);
+
+ if (!s->tmf_bh) {
+ s->tmf_bh = qemu_bh_new(virtio_scsi_do_tmf_bh, s);
+ qemu_bh_schedule(s->tmf_bh);
+ }
+}
+
/* Return 0 if the request is ready to be completed and return to guest;
* -EINPROGRESS if the request is submitted and will be completed later, in the
* case of async cancellation. */
@@ -300,8 +414,6 @@ static int virtio_scsi_do_tmf(VirtIOSCSI *s, VirtIOSCSIReq *req)
{
SCSIDevice *d = virtio_scsi_device_get(s, req->req.tmf.lun);
SCSIRequest *r, *next;
- BusChild *kid;
- int target;
int ret = 0;
virtio_scsi_ctx_check(s, d);
@@ -358,15 +470,9 @@ static int virtio_scsi_do_tmf(VirtIOSCSI *s, VirtIOSCSIReq *req)
break;
case VIRTIO_SCSI_T_TMF_LOGICAL_UNIT_RESET:
- if (!d) {
- goto fail;
- }
- if (d->lun != virtio_scsi_get_lun(req->req.tmf.lun)) {
- goto incorrect_lun;
- }
- s->resetting++;
- device_cold_reset(&d->qdev);
- s->resetting--;
+ case VIRTIO_SCSI_T_TMF_I_T_NEXUS_RESET:
+ virtio_scsi_defer_tmf_to_bh(req);
+ ret = -EINPROGRESS;
break;
case VIRTIO_SCSI_T_TMF_ABORT_TASK_SET:
@@ -409,22 +515,6 @@ static int virtio_scsi_do_tmf(VirtIOSCSI *s, VirtIOSCSIReq *req)
}
break;
- case VIRTIO_SCSI_T_TMF_I_T_NEXUS_RESET:
- target = req->req.tmf.lun[1];
- s->resetting++;
-
- rcu_read_lock();
- QTAILQ_FOREACH_RCU(kid, &s->bus.qbus.children, sibling) {
- SCSIDevice *d1 = SCSI_DEVICE(kid->child);
- if (d1->channel == 0 && d1->id == target) {
- device_cold_reset(&d1->qdev);
- }
- }
- rcu_read_unlock();
-
- s->resetting--;
- break;
-
case VIRTIO_SCSI_T_TMF_CLEAR_ACA:
default:
req->resp.tmf.response = VIRTIO_SCSI_S_FUNCTION_REJECTED;
@@ -654,7 +744,7 @@ static void virtio_scsi_request_cancelled(SCSIRequest *r)
if (!req) {
return;
}
- if (req->dev->resetting) {
+ if (qatomic_read(&req->dev->resetting)) {
req->resp.cmd.response = VIRTIO_SCSI_S_RESET;
} else {
req->resp.cmd.response = VIRTIO_SCSI_S_ABORTED;
@@ -830,9 +920,12 @@ static void virtio_scsi_reset(VirtIODevice *vdev)
VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(vdev);
assert(!s->dataplane_started);
- s->resetting++;
+
+ virtio_scsi_reset_tmf_bh(s);
+
+ qatomic_inc(&s->resetting);
bus_cold_reset(BUS(&s->bus));
- s->resetting--;
+ qatomic_dec(&s->resetting);
vs->sense_size = VIRTIO_SCSI_SENSE_DEFAULT_SIZE;
vs->cdb_size = VIRTIO_SCSI_CDB_DEFAULT_SIZE;
@@ -1052,6 +1145,8 @@ static void virtio_scsi_device_realize(DeviceState *dev, Error **errp)
VirtIOSCSI *s = VIRTIO_SCSI(dev);
Error *err = NULL;
+ QTAILQ_INIT(&s->tmf_bh_list);
+
virtio_scsi_common_realize(dev,
virtio_scsi_handle_ctrl,
virtio_scsi_handle_event,
@@ -1089,6 +1184,8 @@ static void virtio_scsi_device_unrealize(DeviceState *dev)
{
VirtIOSCSI *s = VIRTIO_SCSI(dev);
+ virtio_scsi_reset_tmf_bh(s);
+
qbus_set_hotplug_handler(BUS(&s->bus), NULL);
virtio_scsi_common_unrealize(dev);
}
diff --git a/include/hw/virtio/virtio-scsi.h b/include/hw/virtio/virtio-scsi.h
index a36aad9c86..1c1cd77d6e 100644
--- a/include/hw/virtio/virtio-scsi.h
+++ b/include/hw/virtio/virtio-scsi.h
@@ -75,13 +75,22 @@ struct VirtIOSCSICommon {
VirtQueue **cmd_vqs;
};
+struct VirtIOSCSIReq;
+
struct VirtIOSCSI {
VirtIOSCSICommon parent_obj;
SCSIBus bus;
- int resetting;
+ int resetting; /* written from main loop thread, read from any thread */
bool events_dropped;
+ /*
+ * TMFs deferred to main loop BH. These fields are protected by
+ * virtio_scsi_acquire().
+ */
+ QEMUBH *tmf_bh;
+ QTAILQ_HEAD(, VirtIOSCSIReq) tmf_bh_list;
+
/* Fields for dataplane below */
AioContext *ctx; /* one iothread per virtio-scsi-pci for now */
--
2.39.1

44
qemu-kvm.spec
View File

@ -148,7 +148,7 @@ Obsoletes: %{name}-block-ssh <= %{epoch}:%{version} \
Summary: QEMU is a machine emulator and virtualizer
Name: qemu-kvm
Version: 7.2.0
Release: 11%{?rcrel}%{?dist}%{?cc_suffix}
Release: 12%{?rcrel}%{?dist}%{?cc_suffix}
# Epoch because we pushed a qemu-1.0 package. AIUI this can't ever be dropped
# Epoch 15 used for RHEL 8
# Epoch 17 used for RHEL 9 (due to release versioning offset in RHEL 8.5)
@ -376,6 +376,30 @@ Patch113: kvm-target-s390x-arch_dump-Fix-memory-corruption-in-s390.patch
Patch114: kvm-block-temporarily-hold-the-new-AioContext-of-bs_top-.patch
# For bz#2169904 - [SVVP] job 'Check SMBIOS Table Specific Requirements' failed on win2022
Patch115: kvm-hw-smbios-fix-field-corruption-in-type-4-table.patch
# For bz#2155748 - qemu crash on void blk_drain(BlockBackend *): Assertion qemu_in_main_thread() failed
Patch116: kvm-scsi-protect-req-aiocb-with-AioContext-lock.patch
# For bz#2155748 - qemu crash on void blk_drain(BlockBackend *): Assertion qemu_in_main_thread() failed
Patch117: kvm-dma-helpers-prevent-dma_blk_cb-vs-dma_aio_cancel-rac.patch
# For bz#2155748 - qemu crash on void blk_drain(BlockBackend *): Assertion qemu_in_main_thread() failed
Patch118: kvm-virtio-scsi-reset-SCSI-devices-from-main-loop-thread.patch
# For bz#2175660 - Guest hangs when starting or rebooting
Patch119: kvm-qatomic-add-smp_mb__before-after_rmw.patch
# For bz#2175660 - Guest hangs when starting or rebooting
Patch120: kvm-qemu-thread-posix-cleanup-fix-document-QemuEvent.patch
# For bz#2175660 - Guest hangs when starting or rebooting
Patch121: kvm-qemu-thread-win32-cleanup-fix-document-QemuEvent.patch
# For bz#2175660 - Guest hangs when starting or rebooting
Patch122: kvm-edu-add-smp_mb__after_rmw.patch
# For bz#2175660 - Guest hangs when starting or rebooting
Patch123: kvm-aio-wait-switch-to-smp_mb__after_rmw.patch
# For bz#2175660 - Guest hangs when starting or rebooting
Patch124: kvm-qemu-coroutine-lock-add-smp_mb__after_rmw.patch
# For bz#2175660 - Guest hangs when starting or rebooting
Patch125: kvm-physmem-add-missing-memory-barrier.patch
# For bz#2175660 - Guest hangs when starting or rebooting
Patch126: kvm-async-update-documentation-of-the-memory-barriers.patch
# For bz#2175660 - Guest hangs when starting or rebooting
Patch127: kvm-async-clarify-usage-of-barriers-in-the-polling-case.patch
%if %{have_clang}
BuildRequires: clang
@ -1406,6 +1430,24 @@ useradd -r -u 107 -g qemu -G kvm -d / -s /sbin/nologin \
%endif
%changelog
* Sun Mar 12 2023 Miroslav Rezanina <mrezanin@redhat.com> - 7.2.0-12
- kvm-scsi-protect-req-aiocb-with-AioContext-lock.patch [bz#2155748]
- kvm-dma-helpers-prevent-dma_blk_cb-vs-dma_aio_cancel-rac.patch [bz#2155748]
- kvm-virtio-scsi-reset-SCSI-devices-from-main-loop-thread.patch [bz#2155748]
- kvm-qatomic-add-smp_mb__before-after_rmw.patch [bz#2175660]
- kvm-qemu-thread-posix-cleanup-fix-document-QemuEvent.patch [bz#2175660]
- kvm-qemu-thread-win32-cleanup-fix-document-QemuEvent.patch [bz#2175660]
- kvm-edu-add-smp_mb__after_rmw.patch [bz#2175660]
- kvm-aio-wait-switch-to-smp_mb__after_rmw.patch [bz#2175660]
- kvm-qemu-coroutine-lock-add-smp_mb__after_rmw.patch [bz#2175660]
- kvm-physmem-add-missing-memory-barrier.patch [bz#2175660]
- kvm-async-update-documentation-of-the-memory-barriers.patch [bz#2175660]
- kvm-async-clarify-usage-of-barriers-in-the-polling-case.patch [bz#2175660]
- Resolves: bz#2155748
(qemu crash on void blk_drain(BlockBackend *): Assertion qemu_in_main_thread() failed)
- Resolves: bz#2175660
(Guest hangs when starting or rebooting)
* Mon Mar 06 2023 Miroslav Rezanina <mrezanin@redhat.com> - 7.2.0-11
- kvm-hw-smbios-fix-field-corruption-in-type-4-table.patch [bz#2169904]
- Resolves: bz#2169904