Re: [Qemu-devel] [PATCH] virtio: fix descriptor counting in virtqueue_pop

[Michael S. Tsirkin]

On Fri, Nov 10, 2017 at 03:41:37PM +0000, Stefan Hajnoczi wrote:
> On Thu, Oct 05, 2017 at 08:03:35PM +0200, Alexandre DERUMIER wrote:
> > Hi,
> > 
> > has somebody reviewed this patch ?
> > 
> > I'm also able de reproduce the vm crash like the proxmox user.
> > This patch is fixing it for me too.
> 
> This patch should go through Michael Tsirkin's tree.  I have pinged him
> separately in case this email thread got buried in his inbox.
> 
> Stefan

Isn't this upstream?
I see it as commit 37ef70be6af7e9f2a6f852c68f74bd98dac2664b there.


> > 
> > Regards,
> > 
> > Alexandre
> > 
> > 
> > ----- Mail original -----
> > De: "Wolfgang Bumiller" <address@hidden>
> > À: "qemu-devel" <address@hidden>
> > Cc: "pbonzini" <address@hidden>, "Michael S. Tsirkin" <address@hidden>
> > Envoyé: Mercredi 20 Septembre 2017 08:09:33
> > Objet: [Qemu-devel] [PATCH] virtio: fix descriptor counting in virtqueue_pop
> > 
> > While changing the s/g list allocation, commit 3b3b0628 
> > also changed the descriptor counting to count iovec entries 
> > as split by cpu_physical_memory_map(). Previously only the 
> > actual descriptor entries were counted and the split into 
> > the iovec happened afterwards in virtqueue_map(). 
> > Count the entries again instead to avoid erroneous 
> > "Looped descriptor" errors. 
> > 
> > Reported-by: Hans Middelhoek <address@hidden> 
> > Link: https://forum.proxmox.com/threads/vm-crash-with-memory-hotplug.35904/ 
> > Fixes: 3b3b0628217e ("virtio: slim down allocation of VirtQueueElements") 
> > Signed-off-by: Wolfgang Bumiller <address@hidden> 
> > --- 
> > hw/virtio/virtio.c | 6 +++--- 
> > 1 file changed, 3 insertions(+), 3 deletions(-) 
> > 
> > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c 
> > index 890b4d7eb7..33bb770177 100644 
> > --- a/hw/virtio/virtio.c 
> > +++ b/hw/virtio/virtio.c 
> > @@ -834,7 +834,7 @@ void *virtqueue_pop(VirtQueue *vq, size_t sz) 
> > int64_t len; 
> > VirtIODevice *vdev = vq->vdev; 
> > VirtQueueElement *elem = NULL; 
> > - unsigned out_num, in_num; 
> > + unsigned out_num, in_num, elem_entries; 
> > hwaddr addr[VIRTQUEUE_MAX_SIZE]; 
> > struct iovec iov[VIRTQUEUE_MAX_SIZE]; 
> > VRingDesc desc; 
> > @@ -852,7 +852,7 @@ void *virtqueue_pop(VirtQueue *vq, size_t sz) 
> > smp_rmb(); 
> > 
> > /* When we start there are none of either input nor output. */ 
> > - out_num = in_num = 0; 
> > + out_num = in_num = elem_entries = 0; 
> > 
> > max = vq->vring.num; 
> > 
> > @@ -922,7 +922,7 @@ void *virtqueue_pop(VirtQueue *vq, size_t sz) 
> > } 
> > 
> > /* If we've got too many, that implies a descriptor loop. */ 
> > - if ((in_num + out_num) > max) { 
> > + if (++elem_entries > max) { 
> > virtio_error(vdev, "Looped descriptor"); 
> > goto err_undo_map; 
> > } 
> > -- 
> > 2.11.0 
> > 
> >