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virtio-scsi: protect events_dropped field

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The block layer can invoke the resize callback from any AioContext that
is processing requests. The virtqueue is already protected but the
events_dropped field also needs to be protected against races. Cover it
using the event virtqueue lock because it is closely associated with
accesses to the virtqueue.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20250311132616.1049687-7-stefanha@redhat.com>
Tested-by: Peter Krempa <pkrempa@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2025-03-11 21:26:09 +08:00 • committed by Kevin Wolf
parent b348ca2e04
commit 7d8ab5b2f7
2 changed files with 22 additions and 10 deletions
Download patch file Download diff file Expand all files Collapse all files

29
hw/scsi/virtio-scsi.c
View file

@ -948,7 +948,10 @@ static void virtio_scsi_reset(VirtIODevice *vdev)
vs->sense_size = VIRTIO_SCSI_SENSE_DEFAULT_SIZE;
vs->cdb_size = VIRTIO_SCSI_CDB_DEFAULT_SIZE;
s->events_dropped = false;
WITH_QEMU_LOCK_GUARD(&s->event_lock) {
s->events_dropped = false;
}
}
typedef struct {
@ -978,14 +981,16 @@ static void virtio_scsi_push_event(VirtIOSCSI *s,
}
req = virtio_scsi_pop_req(s, vs->event_vq, &s->event_lock);
if (!req) {
s->events_dropped = true;
return;
}
WITH_QEMU_LOCK_GUARD(&s->event_lock) {
if (!req) {
s->events_dropped = true;
return;
}
if (s->events_dropped) {
event |= VIRTIO_SCSI_T_EVENTS_MISSED;
s->events_dropped = false;
if (s->events_dropped) {
event |= VIRTIO_SCSI_T_EVENTS_MISSED;
s->events_dropped = false;
}
}
if (virtio_scsi_parse_req(req, 0, sizeof(VirtIOSCSIEvent))) {
@ -1014,7 +1019,13 @@ static void virtio_scsi_push_event(VirtIOSCSI *s,
static void virtio_scsi_handle_event_vq(VirtIOSCSI *s, VirtQueue *vq)
{
if (s->events_dropped) {
bool events_dropped;
WITH_QEMU_LOCK_GUARD(&s->event_lock) {
events_dropped = s->events_dropped;
}
if (events_dropped) {
VirtIOSCSIEventInfo info = {
.event = VIRTIO_SCSI_T_NO_EVENT,
};

3
include/hw/virtio/virtio-scsi.h
View file

@ -82,10 +82,11 @@ struct VirtIOSCSI {
SCSIBus bus;
int resetting; /* written from main loop thread, read from any thread */
QemuMutex event_lock; /* protects event_vq and events_dropped */
bool events_dropped;
QemuMutex ctrl_lock; /* protects ctrl_vq */
QemuMutex event_lock; /* protects event_vq */
/*
* TMFs deferred to main loop BH. These fields are protected by