linux-kernel - RE: [PATCH 3/4] VFIO: pci: amend vfio-pci for explicit binding via sysfs only

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Date:	Tue, 29 Oct 2013 03:38:50 +0000
From:	Bhushan Bharat-R65777 <R65777@...escale.com>
To:	Wood Scott-B07421 <B07421@...escale.com>,
	Alex Williamson <alex.williamson@...hat.com>
CC:	Kim Phillips <kim.phillips@...aro.org>,
	Yoder Stuart-B08248 <B08248@...escale.com>,
	"christoffer.dall@...aro.org" <christoffer.dall@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"a.motakis@...tualopensystems.com" <a.motakis@...tualopensystems.com>,
	"agraf@...e.de" <agraf@...e.de>,
	Sethi Varun-B16395 <B16395@...escale.com>,
	"peter.maydell@...aro.org" <peter.maydell@...aro.org>,
	"santosh.shukla@...aro.org" <santosh.shukla@...aro.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
Subject: RE: [PATCH 3/4] VFIO: pci: amend vfio-pci for explicit binding via
 sysfs only



> -----Original Message-----
> From: Wood Scott-B07421
> Sent: Monday, October 28, 2013 11:40 PM
> To: Alex Williamson
> Cc: Kim Phillips; Bhushan Bharat-R65777; Wood Scott-B07421; Yoder Stuart-B08248;
> christoffer.dall@...aro.org; linux-kernel@...r.kernel.org;
> a.motakis@...tualopensystems.com; agraf@...e.de; Sethi Varun-B16395;
> peter.maydell@...aro.org; santosh.shukla@...aro.org; kvm@...r.kernel.org;
> gregkh@...uxfoundation.org
> Subject: Re: [PATCH 3/4] VFIO: pci: amend vfio-pci for explicit binding via
> sysfs only
> 
> On Mon, 2013-10-28 at 13:00 -0500, Scott Wood wrote:
> > On Mon, 2013-10-28 at 11:47 -0600, Alex Williamson wrote:
> > > On Fri, 2013-10-11 at 01:27 -0500, Kim Phillips wrote:
> > > > Force the vfio-pci driver to only be bound explicitly via sysfs to
> > > > avoid conflics with other drivers in the event of a hotplug.
> > >
> > > We can't break userspace, so we can't disable the current method of
> > > binding devices to vfio-pci.  We can add a new method and perhaps
> > > deprecate the existing mechanism to be removed at some point in the
> > > future.  Thanks,
> >
> > I thought the existing method involved using sysfs bind, and this was
> > just eliminating a race.  How does the bind get triggered currently?
> 
> OK, so it seems it's relying on the write to new_id calling driver_attach().
> Sigh.  I guess we could make driver-sysfs-bind-only be settable via sysfs, and
> have new-userspace set both that and PCI_ANY_ID (or the specific ID if userspace
> prefers) via new_id.  The platform bus patches could continue as is, since
> there's no existing mechanism to break.

What about changing the store_new_id() to bypass exact ids check if driver have PCI_ANY_ID?

-Bharat

> 
> -Scott
>