netdev - Re: [PATCH v2] vhost: fix IOTLB locking

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Message-Id: <20181203.155317.2179703794307611009.davem@davemloft.net>
Date:   Mon, 03 Dec 2018 15:53:17 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     jean-philippe.brucker@....com
Cc:     mst@...hat.com, jasowang@...hat.com, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        xiangxia.m.yue@...il.com
Subject: Re: [PATCH v2] vhost: fix IOTLB locking

From: Jean-Philippe Brucker <jean-philippe.brucker@....com>
Date: Fri, 30 Nov 2018 16:05:53 +0000

> Commit 78139c94dc8c ("net: vhost: lock the vqs one by one") moved the vq
> lock to improve scalability, but introduced a possible deadlock in
> vhost-iotlb. vhost_iotlb_notify_vq() now takes vq->mutex while holding
> the device's IOTLB spinlock. And on the vhost_iotlb_miss() path, the
> spinlock is taken while holding vq->mutex.
> 
> Since calling vhost_poll_queue() doesn't require any lock, avoid the
> deadlock by not taking vq->mutex.
> 
> Fixes: 78139c94dc8c ("net: vhost: lock the vqs one by one")
> Acked-by: Jason Wang <jasowang@...hat.com>
> Acked-by: Michael S. Tsirkin <mst@...hat.com>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@....com>

Applied, thank you.