Re: [PATCH V2 4/9] vhost: reset invalidate_count in vhost_set_vring_num_addr()
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2019-07-31 19:37:42
Also in:
kvm, linux-mm, lkml
On Wed, Jul 31, 2019 at 04:32:52PM -0300, Jason Gunthorpe wrote:
On Wed, Jul 31, 2019 at 09:29:28PM +0800, Jason Wang wrote:quoted
On 2019/7/31 下午8:41, Jason Gunthorpe wrote:quoted
On Wed, Jul 31, 2019 at 04:46:50AM -0400, Jason Wang wrote:quoted
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?Correct me if I was wrong. I think it's point 4 described in https://lkml.org/lkml/2019/7/21/25.I'm not sure what that is talking about But this fixes what I described: https://lkml.org/lkml/2019/7/22/554 Jason
These are two reasons for a possible counter imbalance. Unsurprisingly they are both fixed if you reset the counter to 0. -- MST