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Date: Thu, 5 Sep 2013 15:58:54 +0200
From: Stefan Hajnoczi <stefanha@gmail.com>
Message-ID: <20130905135854.GA5190@stefanha-thinkpad.redhat.com>
References: <1378296975-17661-1-git-send-email-cornelia.huck@de.ibm.com>
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In-Reply-To: <1378296975-17661-1-git-send-email-cornelia.huck@de.ibm.com>
Subject: Re: [Qemu-devel] [PATCH RFC] dataplane: Fix startup race.
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To: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: qemu-devel@nongnu.org

On Wed, Sep 04, 2013 at 02:16:15PM +0200, Cornelia Huck wrote:
> Avoid trying to setup dataplane again if dataplane setup is already in
> progress. This may happen if an eventfd is triggered during setup.
> 
> I saw this occasionally with an experimental s390 irqfd implementation:
> 
> virtio_blk_handle_output
> -> virtio_blk_data_plane_start
> -> virtio_ccw_set_host_notifier
> ...
> -> virtio_queue_set_host_notifier_fd_handler
> -> virtio_queue_host_notifier_read
> -> virtio_queue_notify_vq
> -> virtio_blk_handle_output
> -> virtio_blk_data_plane_start
> -> vring_setup
> -> hostmem_init
> -> memory_listener_register
> -> BOOM
> 
> As virtio-ccw tries to follow what virtio-pci does, it might be triggerable
> for other platforms as well.
> 
> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
> ---
>  hw/block/dataplane/virtio-blk.c | 9 +++++++++
>  1 file changed, 9 insertions(+)

Thanks, applied to my block tree:
https://github.com/stefanha/qemu/commits/block

Stefan