From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:55476)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <famz@redhat.com>) id 1YVy0o-00077z-AI
	for qemu-devel@nongnu.org; Thu, 12 Mar 2015 03:58:35 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <famz@redhat.com>) id 1YVy0l-0000Et-26
	for qemu-devel@nongnu.org; Thu, 12 Mar 2015 03:58:34 -0400
Received: from mx1.redhat.com ([209.132.183.28]:38079)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <famz@redhat.com>) id 1YVy0k-0000Em-Qe
	for qemu-devel@nongnu.org; Thu, 12 Mar 2015 03:58:30 -0400
Received: from int-mx11.intmail.prod.int.phx2.redhat.com
	(int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24])
	by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id t2C7wTIx012433
	(version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256
	verify=FAIL)
	for <qemu-devel@nongnu.org>; Thu, 12 Mar 2015 03:58:29 -0400
Date: Thu, 12 Mar 2015 15:58:26 +0800
From: Fam Zheng <famz@redhat.com>
Message-ID: <20150312075826.GB12433@ad.nay.redhat.com>
References: <1426142455-3739-1-git-send-email-famz@redhat.com>
	<20150312082047-mutt-send-email-mst@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20150312082047-mutt-send-email-mst@redhat.com>
Subject: Re: [Qemu-devel] [PATCH] virtio-pci: Clear IRQ at reset
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: qemu-devel@nongnu.org

On Thu, 03/12 08:22, Michael S. Tsirkin wrote:
> On Thu, Mar 12, 2015 at 02:40:55PM +0800, Fam Zheng wrote:
> > Currently we could leave PCI IRQ asserted even after reset, it is safer
> > to clear it.
> > 
> > In the case that a buggy driver has disabled MSI-X unintentially, we may
> > have already injected IRQ in previous virtio_pci_notify, which will not
> > be cleared by guest because it doesn't expect it (i.e. no irq handler).
> > However the driver may eventually notice the unresponsiveness and reset
> > the device, at that point, clearing the irq is meaningful.
> > 
> > Signed-off-by: Fam Zheng <famz@redhat.com>
> 
> I don't get it. interrupts are de-asserted
> in pci core:
> 
> static void pci_do_device_reset(PCIDevice *dev)
> {   
>     int r;
>     
>     pci_device_deassert_intx(dev);
> 
> ...
> }
> 
> why isn't this sufficient?

Becuase it's not called by virtio_pci_reset.

Fam