174 lines
5.5 KiB
Diff
174 lines
5.5 KiB
Diff
From c2d7633ead6e19d4b6af5552ca907ae071b8734b Mon Sep 17 00:00:00 2001
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From: Stefan Hajnoczi <stefanha@redhat.com>
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Date: Tue, 5 Dec 2023 13:19:58 -0500
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Subject: [PATCH 081/101] virtio-scsi: replace AioContext lock with tmf_bh_lock
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RH-Author: Kevin Wolf <kwolf@redhat.com>
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RH-MergeRequest: 214: Remove AioContext lock
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RH-Jira: RHEL-15965
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Commit: [12/26] 8fb375bfd72a491d47321c78078577071a4e90fb (kmwolf/centos-qemu-kvm)
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Protect the Task Management Function BH state with a lock. The TMF BH
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runs in the main loop thread. An IOThread might process a TMF at the
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same time as the TMF BH is running. Therefore tmf_bh_list and tmf_bh
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must be protected by a lock.
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Run TMF request completion in the IOThread using aio_wait_bh_oneshot().
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This avoids more locking to protect the virtqueue and SCSI layer state.
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Reviewed-by: Eric Blake <eblake@redhat.com>
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Reviewed-by: Kevin Wolf <kwolf@redhat.com>
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Message-ID: <20231205182011.1976568-2-stefanha@redhat.com>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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---
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hw/scsi/virtio-scsi.c | 62 ++++++++++++++++++++++-----------
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include/hw/virtio/virtio-scsi.h | 3 +-
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2 files changed, 43 insertions(+), 22 deletions(-)
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diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
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index 9c751bf296..4f8d35facc 100644
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--- a/hw/scsi/virtio-scsi.c
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+++ b/hw/scsi/virtio-scsi.c
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@@ -123,6 +123,30 @@ static void virtio_scsi_complete_req(VirtIOSCSIReq *req)
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virtio_scsi_free_req(req);
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}
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+static void virtio_scsi_complete_req_bh(void *opaque)
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+{
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+ VirtIOSCSIReq *req = opaque;
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+
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+ virtio_scsi_complete_req(req);
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+}
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+
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+/*
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+ * Called from virtio_scsi_do_one_tmf_bh() in main loop thread. The main loop
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+ * thread cannot touch the virtqueue since that could race with an IOThread.
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+ */
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+static void virtio_scsi_complete_req_from_main_loop(VirtIOSCSIReq *req)
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+{
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+ VirtIOSCSI *s = req->dev;
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+
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+ if (!s->ctx || s->ctx == qemu_get_aio_context()) {
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+ /* No need to schedule a BH when there is no IOThread */
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+ virtio_scsi_complete_req(req);
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+ } else {
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+ /* Run request completion in the IOThread */
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+ aio_wait_bh_oneshot(s->ctx, virtio_scsi_complete_req_bh, req);
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+ }
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+}
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+
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static void virtio_scsi_bad_req(VirtIOSCSIReq *req)
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{
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virtio_error(VIRTIO_DEVICE(req->dev), "wrong size for virtio-scsi headers");
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@@ -338,10 +362,7 @@ static void virtio_scsi_do_one_tmf_bh(VirtIOSCSIReq *req)
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out:
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object_unref(OBJECT(d));
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-
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- virtio_scsi_acquire(s);
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- virtio_scsi_complete_req(req);
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- virtio_scsi_release(s);
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+ virtio_scsi_complete_req_from_main_loop(req);
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}
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/* Some TMFs must be processed from the main loop thread */
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@@ -354,18 +375,16 @@ static void virtio_scsi_do_tmf_bh(void *opaque)
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GLOBAL_STATE_CODE();
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- virtio_scsi_acquire(s);
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+ WITH_QEMU_LOCK_GUARD(&s->tmf_bh_lock) {
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+ QTAILQ_FOREACH_SAFE(req, &s->tmf_bh_list, next, tmp) {
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+ QTAILQ_REMOVE(&s->tmf_bh_list, req, next);
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+ QTAILQ_INSERT_TAIL(&reqs, req, next);
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+ }
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- QTAILQ_FOREACH_SAFE(req, &s->tmf_bh_list, next, tmp) {
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- QTAILQ_REMOVE(&s->tmf_bh_list, req, next);
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- QTAILQ_INSERT_TAIL(&reqs, req, next);
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+ qemu_bh_delete(s->tmf_bh);
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+ s->tmf_bh = NULL;
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}
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- qemu_bh_delete(s->tmf_bh);
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- s->tmf_bh = NULL;
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-
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- virtio_scsi_release(s);
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-
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QTAILQ_FOREACH_SAFE(req, &reqs, next, tmp) {
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QTAILQ_REMOVE(&reqs, req, next);
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virtio_scsi_do_one_tmf_bh(req);
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@@ -379,8 +398,7 @@ static void virtio_scsi_reset_tmf_bh(VirtIOSCSI *s)
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GLOBAL_STATE_CODE();
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- virtio_scsi_acquire(s);
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-
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+ /* Called after ioeventfd has been stopped, so tmf_bh_lock is not needed */
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if (s->tmf_bh) {
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qemu_bh_delete(s->tmf_bh);
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s->tmf_bh = NULL;
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@@ -393,19 +411,19 @@ static void virtio_scsi_reset_tmf_bh(VirtIOSCSI *s)
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req->resp.tmf.response = VIRTIO_SCSI_S_TARGET_FAILURE;
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virtio_scsi_complete_req(req);
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}
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-
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- virtio_scsi_release(s);
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}
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static void virtio_scsi_defer_tmf_to_bh(VirtIOSCSIReq *req)
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{
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VirtIOSCSI *s = req->dev;
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- QTAILQ_INSERT_TAIL(&s->tmf_bh_list, req, next);
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+ WITH_QEMU_LOCK_GUARD(&s->tmf_bh_lock) {
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+ QTAILQ_INSERT_TAIL(&s->tmf_bh_list, req, next);
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- if (!s->tmf_bh) {
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- s->tmf_bh = qemu_bh_new(virtio_scsi_do_tmf_bh, s);
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- qemu_bh_schedule(s->tmf_bh);
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+ if (!s->tmf_bh) {
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+ s->tmf_bh = qemu_bh_new(virtio_scsi_do_tmf_bh, s);
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+ qemu_bh_schedule(s->tmf_bh);
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+ }
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}
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}
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@@ -1235,6 +1253,7 @@ static void virtio_scsi_device_realize(DeviceState *dev, Error **errp)
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Error *err = NULL;
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QTAILQ_INIT(&s->tmf_bh_list);
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+ qemu_mutex_init(&s->tmf_bh_lock);
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virtio_scsi_common_realize(dev,
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virtio_scsi_handle_ctrl,
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@@ -1277,6 +1296,7 @@ static void virtio_scsi_device_unrealize(DeviceState *dev)
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qbus_set_hotplug_handler(BUS(&s->bus), NULL);
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virtio_scsi_common_unrealize(dev);
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+ qemu_mutex_destroy(&s->tmf_bh_lock);
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}
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static Property virtio_scsi_properties[] = {
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diff --git a/include/hw/virtio/virtio-scsi.h b/include/hw/virtio/virtio-scsi.h
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index 779568ab5d..da8cb928d9 100644
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--- a/include/hw/virtio/virtio-scsi.h
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+++ b/include/hw/virtio/virtio-scsi.h
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@@ -85,8 +85,9 @@ struct VirtIOSCSI {
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/*
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* TMFs deferred to main loop BH. These fields are protected by
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- * virtio_scsi_acquire().
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+ * tmf_bh_lock.
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*/
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+ QemuMutex tmf_bh_lock;
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QEMUBH *tmf_bh;
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QTAILQ_HEAD(, VirtIOSCSIReq) tmf_bh_list;
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--
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2.39.3
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