[V2,4/9] vhost: reset invalidate_count in vhost_set_vring_num_addr()
diff mbox series

Message ID 20190731084655.7024-5-jasowang@redhat.com
State New
Headers show
Series
  • Fixes for metadata accelreation
Related show

Commit Message

Jason Wang July 31, 2019, 8:46 a.m. UTC
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>
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(+)

Comments

Jason Gunthorpe July 31, 2019, 12:41 p.m. UTC | #1
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?

> 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
>
Jason Wang July 31, 2019, 1:29 p.m. UTC | #2
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@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.

Thanks


>
>> 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
>>
Jason Gunthorpe July 31, 2019, 7:32 p.m. UTC | #3
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 <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
Michael S. Tsirkin July 31, 2019, 7:37 p.m. UTC | #4
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 <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.
Jason Wang Aug. 1, 2019, 5:03 a.m. UTC | #5
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 <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


I'm sorry I miss this, will add your name as reported-by in the next 
version.

Thanks

Patch
diff mbox series

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