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

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Date: Thu, 10 Aug 2023 11:54:44 -0600
From: Alex Williamson <alex.williamson@...hat.com>
To: Jason Gunthorpe <jgg@...dia.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, 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,

Alex