RE: [PATCH V1 vfio 9/9] vfio/virtio: Introduce a vfio driver over virtio devices

From: Parav Pandit <parav@nvidia.com>
To: "Michael S. Tsirkin" <mst@redhat.com>, Yishai Hadas <yishaih@nvidia.com>
Cc: Alex Williamson <alex.williamson@redhat.com>,
	"jasowang@redhat.com" <jasowang@redhat.com>,
	Jason Gunthorpe <jgg@nvidia.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"virtualization@lists.linux-foundation.org" 
	<virtualization@lists.linux-foundation.org>,
	Feng Liu <feliu@nvidia.com>, Jiri Pirko <jiri@nvidia.com>,
	"kevin.tian@intel.com" <kevin.tian@intel.com>,
	"joao.m.martins@oracle.com" <joao.m.martins@oracle.com>,
	"si-wei.liu@oracle.com" <si-wei.liu@oracle.com>,
	Leon Romanovsky <leonro@nvidia.com>,
	Maor Gottlieb <maorg@nvidia.com>
Subject: RE: [PATCH V1 vfio 9/9] vfio/virtio: Introduce a vfio driver over virtio devices
Date: Thu, 26 Oct 2023 12:40:04 +0000	[thread overview]
Message-ID: <PH0PR12MB5481E1AF869C1296B987A34BDCDDA@PH0PR12MB5481.namprd12.prod.outlook.com> (raw)
In-Reply-To: <20231026081033-mutt-send-email-mst@kernel.org>

> From: Michael S. Tsirkin <mst@redhat.com>
> Sent: Thursday, October 26, 2023 5:42 PM
> 
> On Thu, Oct 26, 2023 at 03:08:12PM +0300, Yishai Hadas wrote:
> > > > Makes sense ?
> > > So do I understand correctly that virtio dictates the subsystem
> > > device ID for all subsystem vendor IDs that implement a legacy
> > > virtio interface?  Ok, but this device didn't actually implement a
> > > legacy virtio interface.  The device itself is not tranistional,
> > > we're imposing an emulated transitional interface onto it.  So did
> > > the subsystem vendor agree to have their subsystem device ID managed
> > > by the virtio committee or might we create conflicts?  I imagine we
> > > know we don't have a conflict if we also virtualize the subsystem vendor ID.
> > >
> > The non transitional net device in the virtio spec defined as the
> > below tuple.
> > T_A: VID=0x1AF4, DID=0x1040, Subsys_VID=FOO, Subsys_DID=0x40.
> >
> > And transitional net device in the virtio spec for a vendor FOO is
> > defined
> > as:
> > T_B: VID=0x1AF4,DID=0x1000,Subsys_VID=FOO, subsys_DID=0x1
> >
> > This driver is converting T_A to T_B, which both are defined by the
> > virtio spec.
> > Hence, it does not conflict for the subsystem vendor, it is fine.
> 
> You are talking about legacy guests, what 1.X spec says about them is much less
> important than what guests actually do.
> Check the INF of the open source windows drivers and linux code, at least.

Linux legacy guest has,

static struct pci_device_id virtio_pci_id_table[] = {
        { 0x1af4, PCI_ANY_ID, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0 },
        { 0 },
};
Followed by an open coded driver check for 0x1000 to 0x103f range.
Do you mean windows driver expects specific subsystem vendor id of 0x1af4?