Re: [Qemu-devel] [Qemu-stable] [PULL 10/25] virtio_error: don't invoke status callbacks
Am 13.02.2018 um 23:23 schrieb Michael S. Tsirkin: > On Tue, Feb 13, 2018 at 09:53:58PM +0100, Peter Lieven wrote: >> Am 21.12.2017 um 15:29 schrieb Michael S. Tsirkin: >>> Backends don't need to know what frontend requested a reset, >>> and notifying then from virtio_error is messy because >>> virtio_error itself might be invoked from backend. >>> >>> Let's just set the status directly. >>> >>> Cc: qemu-sta...@nongnu.org >>> Reported-by: Ilya Maximets >>> Signed-off-by: Michael S. Tsirkin >>> --- >>> hw/virtio/virtio.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c >>> index ad564b0..d6002ee 100644 >>> --- a/hw/virtio/virtio.c >>> +++ b/hw/virtio/virtio.c >>> @@ -2469,7 +2469,7 @@ void GCC_FMT_ATTR(2, 3) virtio_error(VirtIODevice >>> *vdev, const char *fmt, ...) >>> va_end(ap); >>> >>> if (virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) { >>> -virtio_set_status(vdev, vdev->status | >>> VIRTIO_CONFIG_S_NEEDS_RESET); >>> +vdev->status = vdev->status | VIRTIO_CONFIG_S_NEEDS_RESET; >>> virtio_notify_config(vdev); >>> } >>> >> >> Is it possible that this patch introduces a stall in I/O and a deadlock on a >> drain all? >> >> I have seen Qemu VMs being I/O stalled and deadlocking on a vm stop command >> in >> >> blk_drain_all. This happened after a longer storage outage. >> >> >> I am asking just theoretically because I have seen this behaviour first when >> we >> >> backported this patch in our stable 2.9 branch. >> >> >> Thank you, >> >> Peter > Well - this patch was introduced to fix a crash, but > a well behaved VM should not trigger VIRTIO_CONFIG_S_NEEDS_RESET - > did you see any error messages in the log when this triggered? You mean in the guest or on the host? On the host I have seen nothing. I actually did not know the reasoning behing this patch. I was just searching for an explaination for the strange I/O stalls that I have seen. And it was not only one guest but a few hundreds. So I think I have to search for another cause. Thank you, Peter
Re: [Qemu-devel] [Qemu-stable] [PULL 10/25] virtio_error: don't invoke status callbacks
On Tue, Feb 13, 2018 at 09:53:58PM +0100, Peter Lieven wrote: > > Am 21.12.2017 um 15:29 schrieb Michael S. Tsirkin: > > Backends don't need to know what frontend requested a reset, > > and notifying then from virtio_error is messy because > > virtio_error itself might be invoked from backend. > > > > Let's just set the status directly. > > > > Cc: qemu-sta...@nongnu.org > > Reported-by: Ilya Maximets > > Signed-off-by: Michael S. Tsirkin > > --- > > hw/virtio/virtio.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c > > index ad564b0..d6002ee 100644 > > --- a/hw/virtio/virtio.c > > +++ b/hw/virtio/virtio.c > > @@ -2469,7 +2469,7 @@ void GCC_FMT_ATTR(2, 3) virtio_error(VirtIODevice > > *vdev, const char *fmt, ...) > > va_end(ap); > > > > if (virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) { > > -virtio_set_status(vdev, vdev->status | > > VIRTIO_CONFIG_S_NEEDS_RESET); > > +vdev->status = vdev->status | VIRTIO_CONFIG_S_NEEDS_RESET; > > virtio_notify_config(vdev); > > } > > > > > Is it possible that this patch introduces a stall in I/O and a deadlock on a > drain all? > > I have seen Qemu VMs being I/O stalled and deadlocking on a vm stop command in > > blk_drain_all. This happened after a longer storage outage. > > > I am asking just theoretically because I have seen this behaviour first when > we > > backported this patch in our stable 2.9 branch. > > > Thank you, > > Peter Well - this patch was introduced to fix a crash, but a well behaved VM should not trigger VIRTIO_CONFIG_S_NEEDS_RESET - did you see any error messages in the log when this triggered? -- MST
Re: [Qemu-devel] [Qemu-stable] [PULL 10/25] virtio_error: don't invoke status callbacks
Am 21.12.2017 um 15:29 schrieb Michael S. Tsirkin: > Backends don't need to know what frontend requested a reset, > and notifying then from virtio_error is messy because > virtio_error itself might be invoked from backend. > > Let's just set the status directly. > > Cc: qemu-sta...@nongnu.org > Reported-by: Ilya Maximets > Signed-off-by: Michael S. Tsirkin > --- > hw/virtio/virtio.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c > index ad564b0..d6002ee 100644 > --- a/hw/virtio/virtio.c > +++ b/hw/virtio/virtio.c > @@ -2469,7 +2469,7 @@ void GCC_FMT_ATTR(2, 3) virtio_error(VirtIODevice > *vdev, const char *fmt, ...) > va_end(ap); > > if (virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) { > -virtio_set_status(vdev, vdev->status | VIRTIO_CONFIG_S_NEEDS_RESET); > +vdev->status = vdev->status | VIRTIO_CONFIG_S_NEEDS_RESET; > virtio_notify_config(vdev); > } > Is it possible that this patch introduces a stall in I/O and a deadlock on a drain all? I have seen Qemu VMs being I/O stalled and deadlocking on a vm stop command in blk_drain_all. This happened after a longer storage outage. I am asking just theoretically because I have seen this behaviour first when we backported this patch in our stable 2.9 branch. Thank you, Peter