linux-kernel - RE: [PATCH] PCI: Support SRIOV on Legacy EndPoint device

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Message-ID: <CY1PR12MB026259439AA9689B7326F4B5FED20@CY1PR12MB0262.namprd12.prod.outlook.com>
Date:	Fri, 5 Feb 2016 16:50:11 +0000
From:	"Zytaruk, Kelly" <Kelly.Zytaruk@....com>
To:	Bjorn Helgaas <helgaas@...nel.org>
CC:	"bhelgaas@...gle.com" <bhelgaas@...gle.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Alex Williamson <alex.williamson@...hat.com>,
	Yu Zhao <yuzhao@...gle.com>
Subject: RE: [PATCH] PCI: Support SRIOV on Legacy EndPoint device



> -----Original Message-----
> From: Bjorn Helgaas [mailto:helgaas@...nel.org]
> Sent: Friday, February 05, 2016 11:47 AM
> To: Zytaruk, Kelly
> Cc: bhelgaas@...gle.com; linux-pci@...r.kernel.org; linux-
> kernel@...r.kernel.org; Alex Williamson; Yu Zhao
> Subject: Re: [PATCH] PCI: Support SRIOV on Legacy EndPoint device
> 
> On Thu, Feb 04, 2016 at 04:21:08PM +0000, Zytaruk, Kelly wrote:
> > > -----Original Message-----
> > > From: Bjorn Helgaas [mailto:helgaas@...nel.org]
> > > Sent: Thursday, February 04, 2016 10:14 AM
> > > To: Zytaruk, Kelly
> > > Cc: bhelgaas@...gle.com; linux-pci@...r.kernel.org; linux-
> > > kernel@...r.kernel.org; Alex Williamson; Yu Zhao
> > > Subject: Re: [PATCH] PCI: Support SRIOV on Legacy EndPoint device
> > >
> > > [+cc Alex, Yu (participants in previous discussion)]
> > >
> > > Hi Kelly,
> > >
> > > On Thu, Feb 04, 2016 at 09:48:26AM -0500, Kelly Zytaruk wrote:
> > > > Some AMD GPUs have hardware support for grapics SRIOV.
> > > > If the GPU has a display output then the GPU needs to support
> > > > Legacy VGA
> > > operation.
> > > > If CLASS_CODE = VGA then the device should have a Port Type =
> > > > Legacy
> > > EndPoint.
> > > > Therefore in order to enable SRIOV on a GPU with a display output
> > > LEGACY_END_POINT is supported as a valid Port Type.
> > > >
> > > > Signed-off-by: Kelly Zytaruk <kelly.zytaruk@....com>
> > >
> > > We had an interesting discussion about this two years ago:
> > >
> http://lkml.kernel.org/r/B756807489D6244883AC0B799A6EEC15EAB2E8@stor
> > > e
> > > xdag02.amd.com
> >
> > Unfortunately 2 years ago I couldn't complete your request as it would
> > have disclosed Information about an unannounced technology that we
> > were working on.  We have recently made that technology public and I
> > can now send you the requested information.
> 
> > > Please include a reference to that discussion in your changelog.  In
> > > that discussion, I also asked for some details (dmesg and lspci
> > > info) that motivate the change, so please collect and add a reference to
> them as well.
> >
> > The information that you ask for is included below.  I have
> > abbreviated it so that this does not become a huge email.  I can send
> > full logs if you want them.
> 
> Can you open a bugzilla at http://bugzilla.kernel.org and attach the full logs
> there?  Then we can include the URL in your patch changelog.

I have never worked with bugzilla before but I will check it out.  So you want me to take the bugzilla URL and paste it into the comments of my patch? Or is this something that you will do?

> 
> > > It's not clear to me why we check the device type at all.  If
> > > there's no spec restriction on the types of devices that can have an
> > > SR-IOV capability, we should consider removing the test altogether
> > > (Alex mentioned this possiblity in the earlier discussion).
> >
> > I am as well not clear why the check is in there.  I would be just as
> > happy either adding TYPE_LEG_END or removing the check all together.
> > I don't know what the side effects of removing the check would be. I
> > don't have any sriov devices other than a graphics card to test with
> > so I wouldn't be able to test other scenarios.
> 
> If we don't have a reason to do the check, I think we should just remove it
> altogether.

So instead of my proposed change do you want me to just remove the check completely and submit a patch for that?

> 
> Bjorn