Re: [PATCH V2 4/9] vhost: reset invalidate_count in vhost_set_vring_num_addr()
On 2019/8/1 上午3:32, Jason Gunthorpe wrote: On Wed, Jul 31, 2019 at 09:29:28PM +0800, Jason Wang wrote: 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 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 I'm sorry I miss this, will add your name as reported-by in the next version. Thanks
Re: [PATCH V2 4/9] vhost: reset invalidate_count in vhost_set_vring_num_addr()
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: > > > > 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 > > > 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
Re: [PATCH V2 4/9] vhost: reset invalidate_count in vhost_set_vring_num_addr()
On Wed, Jul 31, 2019 at 09:29:28PM +0800, Jason Wang wrote: > > 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 > > 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
Re: [PATCH V2 4/9] vhost: reset invalidate_count in vhost_set_vring_num_addr()
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
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
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
Re: [PATCH V2 4/9] vhost: reset invalidate_count in vhost_set_vring_num_addr()
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
Did Michael report this as well?
> Fixes: 7f466032dc9e ("vhost: access vq metadata through kernel virtual
> address")
> Signed-off-by: Jason Wang
> 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
>
[PATCH V2 4/9] vhost: reset invalidate_count in vhost_set_vring_num_addr()
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
Fixes: 7f466032dc9e ("vhost: access vq metadata through kernel virtual address")
Signed-off-by: Jason Wang
---
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
--- a/drivers/vhost/vhost.c
+++ 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
--
2.18.1
