[PATCH] virtio-scsi: set dataplane_started to false upon failure

[Stefan Hajnoczi <stefanha@redhat.com>]

Commit e24a47c5b73e ("virtio-scsi: do not use vring in dataplane") set
dataplane_started to true when virtio_scsi_dataplane_start() fails. This
is likely a typo since dataplane is not functional after failure.

The non-ioeventfd fallback is broken because dataplane_started is true
after virtio_scsi_dataplane_start() failure. As a result, the following
assertion failure occurs when a virtio-scsi device exceeds the open file
descriptor ulimit when setting up notifiers (eventfds):

  $ ulimit -n 104 # exact number can vary based on QEMU version
  $ qemu-system-x86_64 -M q35,accel=kvm -m 1G -cpu host -smp 14 \
         --blockdev file,node-name=drive0,filename=test.img,cache.direct=on,aio=native \
         --blockdev file,node-name=drive1,filename=data01.img,cache.direct=on,aio=native \
         --device virtio-scsi-pci,id=virtio-scsi-pci0 \
         --device scsi-hd,drive=drive0,bus=virtio-scsi-pci0.0 \
         --device virtio-scsi-pci,id=virtio-scsi-pci1 \
         --device scsi-hd,drive=drive1,bus=virtio-scsi-pci1.0
  qemu: virtio-scsi: Failed to set guest notifiers (-24), ensure -accel kvm is set.
  qemu: virtio_bus_start_ioeventfd: failed. Fallback to userspace (slower).
  qemu-system-x86_64: ../hw/scsi/virtio-scsi.c:1017: virtio_scsi_reset: Assertion `!s->dataplane_started' failed.
  Aborted                    (core dumped)

Cc: Paolo Bonzini <pbonzini@redhat.com>
Fixes: e24a47c5b73e ("virtio-scsi: do not use vring in dataplane")
Buglink: https://redhat.atlassian.net/browse/RHEL-193328
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 hw/scsi/virtio-scsi-dataplane.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/scsi/virtio-scsi-dataplane.c b/hw/scsi/virtio-scsi-dataplane.c
index 95f13fb7c28..bcb6e441335 100644
--- a/hw/scsi/virtio-scsi-dataplane.c
+++ b/hw/scsi/virtio-scsi-dataplane.c
@@ -230,7 +230,7 @@ fail_host_notifiers:
 fail_guest_notifiers:
     s->dataplane_fenced = true;
     s->dataplane_starting = false;
-    s->dataplane_started = true;
+    s->dataplane_started = false;
     return -ENOSYS;
 }
 
-- 
2.55.0