netdev - Re: [PATCH V2 4/9] vhost: reset invalidate_count in vhost_set_vring_num

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Message-ID: <0a4deb4e-92e8-44e1-b20e-05767641b6ba@redhat.com>
Date:   Thu, 1 Aug 2019 13:03:24 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     mst@...hat.com, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: 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 <mst@...hat.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