Re: [PATCH V2 4/9] vhost: reset invalidate_count in vhost_set_vring_num_addr()
From: Jason Gunthorpe <jgg@ziepe.ca>
Date: 2019-07-31 12:41:27
Also in:
kvm, linux-mm, lkml
On Wed, Jul 31, 2019 at 04:46:50AM -0400, Jason Wang wrote:
The vhost_set_vring_num_addr() could be called in the middle of invalidate_range_start() and invalidate_range_end(). If we don't reset invalidate_count after the un-registering of MMU notifier, the invalidate_cont will run out of sync (e.g never reach zero). This will in fact disable the fast accessor path. Fixing by reset the count to zero. Reported-by: Michael S. Tsirkin <mst@redhat.com>
Did Michael report this as well?
quoted hunk ↗ jump to hunk
Fixes: 7f466032dc9e ("vhost: access vq metadata through kernel virtual address") Signed-off-by: Jason Wang <jasowang@redhat.com> drivers/vhost/vhost.c | 4 ++++ 1 file changed, 4 insertions(+)diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 2a3154976277..2a7217c33668 100644 +++ b/drivers/vhost/vhost.c@@ -2073,6 +2073,10 @@ static long vhost_vring_set_num_addr(struct vhost_dev *d, d->has_notifier = false; } + /* reset invalidate_count in case we are in the middle of + * invalidate_start() and invalidate_end(). + */ + vq->invalidate_count = 0; vhost_uninit_vq_maps(vq); #endif