From: Amit Shah <amit.shah@redhat.com>
Date: Wed, 16 Mar 2011 13:42:10 +0000 (+0530)
Subject: virtio: Decrement avail idx on buffer detach
X-Git-Tag: v2.6.39-rc5~28^2~2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b3258ff1d6086bd2b9eeb556844a868ad7d49bc8;p=pandora-kernel.git

virtio: Decrement avail idx on buffer detach

When detaching a buffer from a vq, the avail.idx value should be
decremented as well.

This was noticed by hot-unplugging a virtio console port and then
plugging in a new one on the same number (re-using the vqs which were
just 'disowned').  qemu reported

   'Guest moved used index from 0 to 256'

when any IO was attempted on the new port.

CC: stable@kernel.org
Reported-by: juzhang <juzhang@redhat.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---

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