qemu-kvm/SOURCES/kvm-virtio-blk-avoid-using-ioeventfd-state-in-irqfd-cond.patch

73 lines
2.6 KiB
Diff

From f62b56c68d50a149a07e15797bf3605e63b2c501 Mon Sep 17 00:00:00 2001
From: Stefan Hajnoczi <stefanha@redhat.com>
Date: Mon, 22 Jan 2024 12:26:25 -0500
Subject: [PATCH 4/6] virtio-blk: avoid using ioeventfd state in irqfd
conditional
RH-Author: Stefan Hajnoczi <stefanha@redhat.com>
RH-MergeRequest: 224: virtio-blk: avoid using ioeventfd state in irqfd conditional
RH-Jira: RHEL-15394
RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
RH-Acked-by: Hanna Czenczek <hreitz@redhat.com>
RH-Commit: [1/1] 8f24084669db52457e55e2523b9f56f5560dd6ce (stefanha/centos-stream-qemu-kvm)
Requests that complete in an IOThread use irqfd to notify the guest
while requests that complete in the main loop thread use the traditional
qdev irq code path. The reason for this conditional is that the irq code
path requires the BQL:
if (s->ioeventfd_started && !s->ioeventfd_disabled) {
virtio_notify_irqfd(vdev, req->vq);
} else {
virtio_notify(vdev, req->vq);
}
There is a corner case where the conditional invokes the irq code path
instead of the irqfd code path:
static void virtio_blk_stop_ioeventfd(VirtIODevice *vdev)
{
...
/*
* Set ->ioeventfd_started to false before draining so that host notifiers
* are not detached/attached anymore.
*/
s->ioeventfd_started = false;
/* Wait for virtio_blk_dma_restart_bh() and in flight I/O to complete */
blk_drain(s->conf.conf.blk);
During blk_drain() the conditional produces the wrong result because
ioeventfd_started is false.
Use qemu_in_iothread() instead of checking the ioeventfd state.
Cc: qemu-stable@nongnu.org
Buglink: https://issues.redhat.com/browse/RHEL-15394
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20240122172625.415386-1-stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit bfa36802d1704fc413c590ebdcc4e5ae0eacf439)
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
hw/block/virtio-blk.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 7fdeaf2d12..2ae2f6a823 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -66,7 +66,7 @@ static void virtio_blk_req_complete(VirtIOBlockReq *req, unsigned char status)
iov_discard_undo(&req->inhdr_undo);
iov_discard_undo(&req->outhdr_undo);
virtqueue_push(req->vq, &req->elem, req->in_len);
- if (s->ioeventfd_started && !s->ioeventfd_disabled) {
+ if (qemu_in_iothread()) {
virtio_notify_irqfd(vdev, req->vq);
} else {
virtio_notify(vdev, req->vq);
--
2.39.3