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From: "Michael S. Tsirkin" <mst@redhat.com>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jason Wang <jasowang@redhat.com>,
	kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org
Subject: Re: [PATCH V2 4/9] vhost: reset invalidate_count in vhost_set_vring_num_addr()
Date: Wed, 31 Jul 2019 15:37:34 -0400	[thread overview]
Message-ID: <20190731153640-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20190731193252.GH3946@ziepe.ca>

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.

-- 
MST

  reply	other threads:[~2019-07-31 19:37 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-31  8:46 [PATCH V2 0/9] Fixes for metadata accelreation Jason Wang
2019-07-31  8:46 ` [PATCH V2 1/9] vhost: don't set uaddr for invalid address Jason Wang
2019-07-31  8:46 ` [PATCH V2 2/9] vhost: validate MMU notifier registration Jason Wang
2019-07-31  8:46 ` [PATCH V2 3/9] vhost: fix vhost map leak Jason Wang
2019-07-31  8:46 ` [PATCH V2 4/9] vhost: reset invalidate_count in vhost_set_vring_num_addr() Jason Wang
2019-07-31 12:41   ` Jason Gunthorpe
2019-07-31 13:29     ` Jason Wang
2019-07-31 19:32       ` Jason Gunthorpe
2019-07-31 19:37         ` Michael S. Tsirkin [this message]
2019-08-01  5:03         ` Jason Wang
2019-07-31  8:46 ` [PATCH V2 5/9] vhost: mark dirty pages during map uninit Jason Wang
2019-07-31  8:46 ` [PATCH V2 6/9] vhost: don't do synchronize_rcu() in vhost_uninit_vq_maps() Jason Wang
2019-07-31  8:46 ` [PATCH V2 7/9] vhost: do not use RCU to synchronize MMU notifier with worker Jason Wang
2019-07-31  8:50   ` Jason Wang
2019-07-31 12:39   ` Jason Gunthorpe
2019-07-31 13:28     ` Jason Wang
2019-07-31 19:30       ` Jason Gunthorpe
2019-08-01  5:02         ` Jason Wang
2019-08-01 14:15           ` Jason Gunthorpe
2019-08-02  9:40             ` Jason Wang
2019-08-02 12:46               ` Jason Gunthorpe
2019-08-02 14:27                 ` Michael S. Tsirkin
2019-08-02 17:24                   ` Jason Gunthorpe
2019-08-03 21:36                     ` Michael S. Tsirkin
2019-08-04  0:14                       ` Jason Gunthorpe
2019-08-04  8:07                         ` Michael S. Tsirkin
2019-08-05  4:39                           ` Jason Wang
2019-08-06 11:53                           ` Jason Gunthorpe
2019-08-06 13:36                             ` Michael S. Tsirkin
2019-08-06 13:40                               ` Jason Gunthorpe
2019-08-05  4:36                   ` Jason Wang
2019-08-05  4:41                     ` Jason Wang
2019-08-05  6:40                       ` Michael S. Tsirkin
2019-08-05  8:24                         ` Jason Wang
2019-08-05  6:30                     ` Michael S. Tsirkin
2019-08-05  8:22                       ` Jason Wang
2019-08-05  4:20                 ` Jason Wang
2019-08-06 12:04                   ` Jason Gunthorpe
2019-08-07  6:49                     ` Jason Wang
2019-08-02 14:03               ` Michael S. Tsirkin
2019-08-05  4:33                 ` Jason Wang
2019-08-05  6:28                   ` Michael S. Tsirkin
2019-08-05  8:21                     ` Jason Wang
2019-07-31 18:29   ` Michael S. Tsirkin
2019-08-01  8:06     ` Jason Wang
2019-08-03 21:54       ` Michael S. Tsirkin
2019-08-05  8:18         ` Jason Wang
2019-07-31  8:46 ` [PATCH V2 8/9] vhost: correctly set dirty pages in MMU notifiers callback Jason Wang
2019-07-31  8:46 ` [PATCH V2 9/9] vhost: do not return -EAGIAN for non blocking invalidation too early Jason Wang
2019-07-31  9:59   ` Stefano Garzarella
2019-07-31 10:05     ` Jason Wang

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