| Message ID | 1473263485-17084-1-git-send-email-stefanha@redhat.com |
|---|---|
| State | New |
| Headers | show |
On Wed, Sep 7, 2016 at 11:51 AM, Stefan Hajnoczi <stefanha@redhat.com> wrote: > vq->inuse must be zeroed upon device reset like most other virtqueue > fields. > > In theory, virtio_reset() just needs assert(vq->inuse == 0) since > devices must clean up in-flight requests during reset (requests cannot > not be leaked!). > > In practice, it is difficult to achieve vq->inuse == 0 across reset > because balloon, blk, 9p, etc implement various different strategies for > cleaning up requests. Most devices call g_free(elem) directly without > telling virtio.c that the VirtQueueElement is cleaned up. Therefore > vq->inuse is not decremented during reset. > > This patch zeroes vq->inuse and trusts that devices are not leaking > VirtQueueElements across reset. > > I will send a follow-up series that refactors request life-cycle across > all devices and converts vq->inuse = 0 into assert(vq->inuse == 0) but > this more invasive approach is not appropriate for stable trees. > > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> > --- > hw/virtio/virtio.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c > index 74c085c..e8a13a5 100644 > --- a/hw/virtio/virtio.c > +++ b/hw/virtio/virtio.c > @@ -822,6 +822,7 @@ void virtio_reset(void *opaque) > vdev->vq[i].signalled_used_valid = false; > vdev->vq[i].notification = true; > vdev->vq[i].vring.num = vdev->vq[i].vring.num_default; > + vdev->vq[i].inuse = 0; > } > } > > -- > 2.7.4 CCing qemu-stable
On Wed, Sep 7, 2016 at 5:54 PM, Stefan Hajnoczi <stefanha@gmail.com> wrote: > On Wed, Sep 7, 2016 at 11:51 AM, Stefan Hajnoczi <stefanha@redhat.com> wrote: >> vq->inuse must be zeroed upon device reset like most other virtqueue >> fields. >> >> In theory, virtio_reset() just needs assert(vq->inuse == 0) since >> devices must clean up in-flight requests during reset (requests cannot >> not be leaked!). >> >> In practice, it is difficult to achieve vq->inuse == 0 across reset >> because balloon, blk, 9p, etc implement various different strategies for >> cleaning up requests. Most devices call g_free(elem) directly without >> telling virtio.c that the VirtQueueElement is cleaned up. Therefore >> vq->inuse is not decremented during reset. >> >> This patch zeroes vq->inuse and trusts that devices are not leaking >> VirtQueueElements across reset. >> >> I will send a follow-up series that refactors request life-cycle across >> all devices and converts vq->inuse = 0 into assert(vq->inuse == 0) but >> this more invasive approach is not appropriate for stable trees. >> >> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> >> --- >> hw/virtio/virtio.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c >> index 74c085c..e8a13a5 100644 >> --- a/hw/virtio/virtio.c >> +++ b/hw/virtio/virtio.c >> @@ -822,6 +822,7 @@ void virtio_reset(void *opaque) >> vdev->vq[i].signalled_used_valid = false; >> vdev->vq[i].notification = true; >> vdev->vq[i].vring.num = vdev->vq[i].vring.num_default; >> + vdev->vq[i].inuse = 0; >> } >> } >> >> -- >> 2.7.4 > > CCing qemu-stable Reviewed-by: Ladi Prosek <lprosek@redhat.com>
On Wed, 7 Sep 2016 11:51:25 -0400 Stefan Hajnoczi <stefanha@redhat.com> wrote: > vq->inuse must be zeroed upon device reset like most other virtqueue > fields. > > In theory, virtio_reset() just needs assert(vq->inuse == 0) since > devices must clean up in-flight requests during reset (requests cannot > not be leaked!). > > In practice, it is difficult to achieve vq->inuse == 0 across reset > because balloon, blk, 9p, etc implement various different strategies for > cleaning up requests. Most devices call g_free(elem) directly without > telling virtio.c that the VirtQueueElement is cleaned up. Therefore > vq->inuse is not decremented during reset. > > This patch zeroes vq->inuse and trusts that devices are not leaking > VirtQueueElements across reset. > > I will send a follow-up series that refactors request life-cycle across > all devices and converts vq->inuse = 0 into assert(vq->inuse == 0) but > this more invasive approach is not appropriate for stable trees. > > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> > --- > hw/virtio/virtio.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c > index 74c085c..e8a13a5 100644 > --- a/hw/virtio/virtio.c > +++ b/hw/virtio/virtio.c > @@ -822,6 +822,7 @@ void virtio_reset(void *opaque) > vdev->vq[i].signalled_used_valid = false; > vdev->vq[i].notification = true; > vdev->vq[i].vring.num = vdev->vq[i].vring.num_default; > + vdev->vq[i].inuse = 0; > } > } > This looks sane as a minimal change, and survives my smoketests. Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 74c085c..e8a13a5 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -822,6 +822,7 @@ void virtio_reset(void *opaque) vdev->vq[i].signalled_used_valid = false; vdev->vq[i].notification = true; vdev->vq[i].vring.num = vdev->vq[i].vring.num_default; + vdev->vq[i].inuse = 0; } }
vq->inuse must be zeroed upon device reset like most other virtqueue fields. In theory, virtio_reset() just needs assert(vq->inuse == 0) since devices must clean up in-flight requests during reset (requests cannot not be leaked!). In practice, it is difficult to achieve vq->inuse == 0 across reset because balloon, blk, 9p, etc implement various different strategies for cleaning up requests. Most devices call g_free(elem) directly without telling virtio.c that the VirtQueueElement is cleaned up. Therefore vq->inuse is not decremented during reset. This patch zeroes vq->inuse and trusts that devices are not leaking VirtQueueElements across reset. I will send a follow-up series that refactors request life-cycle across all devices and converts vq->inuse = 0 into assert(vq->inuse == 0) but this more invasive approach is not appropriate for stable trees. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> --- hw/virtio/virtio.c | 1 + 1 file changed, 1 insertion(+)