netdev - RE: [RFC net-next PATCH 1/4] pci: Add flag indicating device has been assigned by KVM

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Date:	Fri, 29 Jul 2011 09:54:56 -0700
From:	"Rose, Gregory V" <gregory.v.rose@...el.com>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Ian Campbell <ijc@...lion.org.uk>
CC:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"bhutchings@...arflare.com" <bhutchings@...arflare.com>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: RE: [RFC net-next PATCH 1/4] pci: Add flag indicating device has
 been assigned by KVM

> -----Original Message-----
> From: Jesse Barnes [mailto:jbarnes@...tuousgeek.org]
> Sent: Friday, July 29, 2011 9:52 AM
> To: Ian Campbell
> Cc: Rose, Gregory V; Konrad Rzeszutek Wilk; netdev@...r.kernel.org;
> davem@...emloft.net; bhutchings@...arflare.com; Kirsher, Jeffrey T; linux-
> pci@...r.kernel.org
> Subject: Re: [RFC net-next PATCH 1/4] pci: Add flag indicating device has
> been assigned by KVM
> 
> On Thu, 28 Jul 2011 16:11:17 +0100
> Ian Campbell <ijc@...lion.org.uk> wrote:
> 
> > On Wed, 2011-07-27 at 15:17 -0700, Greg Rose wrote:
> > > Device drivers that create and destroy SR-IOV virtual functions via
> > > calls to pci_enable_sriov() and pci_disable_sriov can cause
> catastrophic
> > > failures if they attempt to destroy VFs while they are assigned to
> > > guest virtual machines.  By adding a flag for use by the KVM module
> > > to indicate that a device is assigned a device driver can check that
> > > flag and avoid destroying VFs while they are assigned and avoid system
> > > failures.
> > >
> > > Signed-off-by: Greg Rose <gregory.v.rose@...el.com>
> > > ---
> > >
> > >  include/linux/pci.h     |    2 ++
> >
> > I added Jesse and linux-pci to CC.
> >
> > >  virt/kvm/assigned-dev.c |    2 ++
> > >  virt/kvm/iommu.c        |    4 ++++
> > >  3 files changed, 8 insertions(+), 0 deletions(-)
> >
> > I suppose this would also be useful in Xen's pciback or any other system
> > which does passthrough? (Konrad CC'd for pciback)
> >
> > Is there some common lower layer we could hook this in to? (does
> > iommu_attach/detach_device make sense?) Or shall we just add the flag
> > manipulations to pciback as well?
> >
> > Ian.
> >
> > >
> > > diff --git a/include/linux/pci.h b/include/linux/pci.h
> > > index 2d29218..a297ca2 100644
> > > --- a/include/linux/pci.h
> > > +++ b/include/linux/pci.h
> > > @@ -174,6 +174,8 @@ enum pci_dev_flags {
> > >  	PCI_DEV_FLAGS_MSI_INTX_DISABLE_BUG = (__force pci_dev_flags_t) 1,
> > >  	/* Device configuration is irrevocably lost if disabled into D3 */
> > >  	PCI_DEV_FLAGS_NO_D3 = (__force pci_dev_flags_t) 2,
> > > +	/* Provide indication device is assigned by KVM */
> > > +	PCI_DEV_FLAGS_ASSIGNED = (__force pci_dev_flags_t) 4,
> > >  };
> 
> Looks fine, but I'd make the comment less redundant with the code, e.g.
> "set when the device is assigned to a guest instance" or somesuch.

Sure, sounds good to me.

Rev 2 of the RFC patches will be out in a couple of weeks, I'm away next week.

Thanks,

- Greg

> 
> --
> Jesse Barnes, Intel Open Source Technology Center
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