linux-kernel - RE: [PATCH v3 3/3] QEMU-AER: Qemu changes to support AER for VFIO-PCI devices

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Message-ID: <F9E001219150CB45BEDC82A650F360C9014B43DC@G9W0717.americas.hpqcorp.net>
Date:	Tue, 5 Feb 2013 10:59:41 +0000
From:	"Pandarathil, Vijaymohan R" <vijaymohan.pandarathil@...com>
To:	Gleb Natapov <gleb@...hat.com>
CC:	Blue Swirl <blauwirbel@...il.com>,
	Alex Williamson <alex.williamson@...hat.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"Ortiz, Lance E" <lance.oritz@...com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"qemu-devel@...gnu.org" <qemu-devel@...gnu.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3 3/3] QEMU-AER: Qemu changes to support AER for
 VFIO-PCI devices



> -----Original Message-----
> From: Gleb Natapov [mailto:gleb@...hat.com]
> Sent: Tuesday, February 05, 2013 1:21 AM
> To: Pandarathil, Vijaymohan R
> Cc: Blue Swirl; Alex Williamson; Bjorn Helgaas; Ortiz, Lance E;
> kvm@...r.kernel.org; qemu-devel@...gnu.org; linux-pci@...r.kernel.org;
> linux-kernel@...r.kernel.org
> Subject: Re: [PATCH v3 3/3] QEMU-AER: Qemu changes to support AER for VFIO-
> PCI devices
> 
> On Tue, Feb 05, 2013 at 09:05:19AM +0000, Pandarathil, Vijaymohan R wrote:
> >
> >
> > > -----Original Message-----
> > > From: Gleb Natapov [mailto:gleb@...hat.com]
> > > Sent: Tuesday, February 05, 2013 12:05 AM
> > > To: Blue Swirl
> > > Cc: Pandarathil, Vijaymohan R; Alex Williamson; Bjorn Helgaas; Ortiz,
> Lance
> > > E; kvm@...r.kernel.org; qemu-devel@...gnu.org; linux-
> pci@...r.kernel.org;
> > > linux-kernel@...r.kernel.org
> > > Subject: Re: [PATCH v3 3/3] QEMU-AER: Qemu changes to support AER for
> VFIO-
> > > PCI devices
> > >
> > > On Sun, Feb 03, 2013 at 04:36:11PM +0000, Blue Swirl wrote:
> > > > On Sun, Feb 3, 2013 at 2:10 PM, Pandarathil, Vijaymohan R
> > > > <vijaymohan.pandarathil@...com> wrote:
> > > > >         - Create eventfd per vfio device assigned to a guest and
> > > register an
> > > > >           event handler
> > > > >
> > > > >         - This fd is passed to the vfio_pci driver through the
> SET_IRQ
> > > ioctl
> > > > >
> > > > >         - When the device encounters an error, the eventfd is
> signalled
> > > > >           and the qemu eventfd handler gets invoked.
> > > > >
> > > > >         - In the handler decide what action to take. Current action
> > > taken
> > > > >           is to terminate the guest.
> > > >
> > > > Usually this is not OK, but I guess this is not guest triggerable.
> > > >
> > > Still not OK. Why not stop a guest with appropriate stop reason?
> >
> > The thinking was that since this is a hardware error, we would want to
> stop the guest at the earliest. The hw_error() routine which aborts the
> qemu process was suggested by Alex and that seemed appropriate. Earlier I
> was using qemu_system_shutdown_request().  Any suggestions ?
> >
> I am thinking vm_stop(). Stopping SMP guest (and UP too in fact)
> involves sending IPIs to other cpus running guest's vcpus. Both exit()
> and vm_stop() will do it, but former is implicitly in the kernel and
> later is explicitly in QEMU.

I had used vm_stop(RUN_STATE_SHUTDOWN) earlier in my code. But while testing, guest ended up in a hang rather than exiting. There seems to some cleanup work which is being done as part of vm_stop. In our case, we wanted the guest to exit immediately. So use of hw_error() seemed appropriate.

Thoughts ?

Vijay

> 
> --
> 			Gleb.
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