From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [PATCH 2/2] tcm_vhost: Initialize vq->last_used_idx when set
	endpoint
Date: Mon, 25 Mar 2013 13:16:11 +0200
Message-ID: <20130325111611.GD9221@redhat.com>
References: <1363920748-32139-1-git-send-email-asias@redhat.com>
	<1363920748-32139-3-git-send-email-asias@redhat.com>
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To: Asias He <asias@redhat.com>
Cc: kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, target-devel@vger.kernel.org, Stefan Hajnoczi <stefanha@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>
List-Id: virtualization@lists.linuxfoundation.org

On Fri, Mar 22, 2013 at 10:52:28AM +0800, Asias He wrote:
> This patch fixes guest hang when booting seabios and guest.
> 
>   [    0.576238] scsi0 : Virtio SCSI HBA
>   [    0.616754] virtio_scsi virtio1: request:id 0 is not a head!
> 
> vq->last_used_idx is initialized only when /dev/vhost-scsi is
> opened or closed.
> 
>    vhost_scsi_open -> vhost_dev_init() -> vhost_vq_reset()
>    vhost_scsi_release() -> vhost_dev_cleanup -> vhost_vq_reset()
> 
> So, when guest talks to tcm_vhost after seabios does, vq->last_used_idx
> still contains the old valule for seabios. This confuses guest.
> 
> Fix this by calling vhost_init_used() to init vq->last_used_idx when
> we set endpoint.
> 
> Signed-off-by: Asias He <asias@redhat.com>

Good catch, thanks.

Acked-by: Michael S. Tsirkin <mst@redhat.com>

Nicholas can you pick this one up for 3.9 please?

> ---
>  drivers/vhost/tcm_vhost.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
> index 099feef..0524267 100644
> --- a/drivers/vhost/tcm_vhost.c
> +++ b/drivers/vhost/tcm_vhost.c
> @@ -848,6 +848,7 @@ static int vhost_scsi_set_endpoint(
>  			/* Flushing the vhost_work acts as synchronize_rcu */
>  			mutex_lock(&vq->mutex);
>  			rcu_assign_pointer(vq->private_data, vs);
> +			vhost_init_used(vq);
>  			mutex_unlock(&vq->mutex);
>  		}
>  		ret = 0;
> -- 
> 1.8.1.4