Re: [Qemu-devel] [RFC-v2 1/6] msix: Work-around for vhost-scsi with KVM in-kernel MSI injection

["Nicholas A. Bellinger" <nab@linux-iscsi.org>]

On Mon, 2012-08-13 at 21:17 +0300, Michael S. Tsirkin wrote:
> On Mon, Aug 13, 2012 at 08:06:17PM +0200, Jan Kiszka wrote:
> > On 2012-08-13 20:03, Michael S. Tsirkin wrote:
> > > On Mon, Aug 13, 2012 at 02:06:10PM +0200, Jan Kiszka wrote:
> > >> On 2012-08-13 10:35, Nicholas A. Bellinger wrote:
> > >>> From: Nicholas Bellinger <nab@linux-iscsi.org>
> > >>>
> > >>> This is required to get past the following assert with:
> > >>>
> > >>> commit 1523ed9e1d46b0b54540049d491475ccac7e6421
> > >>> Author: Jan Kiszka <jan.kiszka@siemens.com>
> > >>> Date:   Thu May 17 10:32:39 2012 -0300
> > >>>
> > >>>     virtio/vhost: Add support for KVM in-kernel MSI injection
> > >>>
> > >>> Cc: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
> > >>> Cc: Jan Kiszka <jan.kiszka@siemens.com>
> > >>> Cc: Paolo Bonzini <pbonzini@redhat.com>
> > >>> Cc: Anthony Liguori <aliguori@us.ibm.com>
> > >>> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
> > >>> ---
> > >>>  hw/msix.c |    3 +++
> > >>>  1 files changed, 3 insertions(+), 0 deletions(-)
> > >>>
> > >>> diff --git a/hw/msix.c b/hw/msix.c
> > >>> index 800fc32..c1e6dc3 100644
> > >>> --- a/hw/msix.c
> > >>> +++ b/hw/msix.c
> > >>> @@ -544,6 +544,9 @@ void msix_unset_vector_notifiers(PCIDevice *dev)
> > >>>  {
> > >>>      int vector;
> > >>>  
> > >>> +    if (!dev->msix_vector_use_notifier && !dev->msix_vector_release_notifier)
> > >>> +        return;
> > >>> +
> > >>>      assert(dev->msix_vector_use_notifier &&
> > >>>             dev->msix_vector_release_notifier);
> > >>>  
> > >>>
> > >>
> > >> I think to remember pointing out that there is a bug somewhere in the
> > >> reset code which deactivates a non-active vhost instance, no?
> > >>
> > >> Jan
> > > 
> > > Could not find it. Could you dig it up pls?
> > 
> > http://thread.gmane.org/gmane.linux.scsi.target.devel/2277/focus=2309
> > 
> > Jan
> 
> Ah yes. So let's not work around, need to get to the bottom of that.
> 

Ok, so the assert being triggered in msix_unset_vector_notifiers()
appears to have been a side effect of the memory corruption bug in
virtio-scsi fixed in Patch #6, and is no longer required to start
vhost-scsi with the bugfix in place.

That said, dropping this patch for RFC-v3..