netdev - Re: [PATCH v14 vfio 6/8] vfio/pds: Add support for dirty page tracking

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Date: Thu, 10 Aug 2023 15:11:43 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Alex Williamson <alex.williamson@...hat.com>
Cc: Christoph Hellwig <hch@....de>, "Tian, Kevin" <kevin.tian@...el.com>,
	Brett Creeley <bcreeley@....com>,
	Brett Creeley <brett.creeley@....com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"yishaih@...dia.com" <yishaih@...dia.com>,
	"shameerali.kolothum.thodi@...wei.com" <shameerali.kolothum.thodi@...wei.com>,
	"horms@...nel.org" <horms@...nel.org>,
	"shannon.nelson@....com" <shannon.nelson@....com>
Subject: Re: [PATCH v14 vfio 6/8] vfio/pds: Add support for dirty page
 tracking

On Thu, Aug 10, 2023 at 11:54:44AM -0600, Alex Williamson wrote:
> On Thu, 10 Aug 2023 14:43:04 -0300
> Jason Gunthorpe <jgg@...dia.com> wrote:
> 
> > On Thu, Aug 10, 2023 at 11:40:08AM -0600, Alex Williamson wrote:
> > 
> > > PCI Express® Base Specification Revision 6.0.1, pg 1461:
> > > 
> > >   9.3.3.11 VF Device ID (Offset 1Ah)
> > > 
> > >   This field contains the Device ID that should be presented for every VF to the SI.
> > > 
> > >   VF Device ID may be different from the PF Device ID...
> > > 
> > > That?  Thanks,  
> > 
> > NVMe matches using the class code, IIRC there is language requiring
> > the class code to be the same.
> 
> Ok, yes:
> 
>   7.5.1.1.6 Class Code Register (Offset 09h)
>   ...
>   The field in a PF and its associated VFs must return the same value
>   when read.
> 
> Seems limiting, but it's indeed there.  We've got a lot of cleanup to
> do if we're going to start rejecting drivers for devices with PCI
> spec violations though ;)  Thanks,

Well.. If we defacto say that Linux is endorsing ignoring this part of
the spec then I predict we will see more vendors follow this approach.

Jason