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From: "Nicholas A. Bellinger" <nab@linux-iscsi.org>
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Date: Wed, 27 Mar 2013 16:24:22 -0700
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Subject: Re: [Qemu-devel] [PATCH 2/3] vhost-scsi: new device supporting the
 tcm_vhost Linux kernel module
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: kvm-devel <kvm@vger.kernel.org>, qemu-devel <qemu-devel@nongnu.org>, lf-virt <virtualization@lists.linux-foundation.org>, Anthony Liguori <aliguori@linux.vnet.ibm.com>, target-devel <target-devel@vger.kernel.org>, Stefan Hajnoczi <stefanha@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Asias He <asias@redhat.com>

On Thu, 2013-03-28 at 00:53 +0200, Michael S. Tsirkin wrote:
> On Thu, Mar 28, 2013 at 12:50:21AM +0200, Michael S. Tsirkin wrote:
> > On Wed, Mar 27, 2013 at 03:45:42PM -0700, Nicholas A. Bellinger wrote:
> > > On Thu, 2013-03-28 at 00:28 +0200, Michael S. Tsirkin wrote:
> > > > On Wed, Mar 27, 2013 at 09:59:45PM +0000, Nicholas A. Bellinger wrote:
> > > > > From: Paolo Bonzini <pbonzini@redhat.com>
> > > > > 
> > > > > The WWPN specified in configfs is passed to "-device vhost-scsi-pci".
> > > > > The tgpt field of the SET_ENDPOINT ioctl is obsolete now, so it is not
> > > > > available from the QEMU command-line.  Instead, I hardcode it to zero.
> > > > > 
> > > > > Changes in V4:
> > > > >    - Set event_idx=off by default (nab, thanks asias)
> > > > 
> > > > Why? What's going on here?
> > > > 
> > > 
> > > Not disabling event_idx by default, or disabling from the command line
> > > ends up resulting in ->handle_kick() not getting called for subsequent
> > > commands..
> > > 
> > > I spent some time trying to track this down recently with no luck, and
> > > AFAICT it's always been required in order for vhost-scsi to function.
> > 
> > Hmm this is a bug in kernel then. A better work-around is
> > to disable EVENT_IDX in kernel. Let's do it for 3.9?
> 
> But before we do, can you check that SET_FEATURES is
> called with this bit set if you enable event_idx?
> If not that's your bug then ...
> 

Ok, SET_FEATURES is currently not setting any bits at all based upon
vhost_dev->features, so it looks like a vhost-scsi-pci bug..