On 2019/7/31 下午8:41, Jason Gunthorpe wrote:
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@xxxxxxxxxx>
Did Michael report this as well?
Correct me if I was wrong. I think it's point 4 described in
https://lkml.org/lkml/2019/7/21/25.
Thanks
Fixes: 7f466032dc9e ("vhost: access vq metadata through kernel virtual address")
Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
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
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