Re: [RFC][PATCH 2/3] docs/specs: Add specification of ivshmem device revision 2

From: "Daniel P. Berrangé" <berrange@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: liang yan <lyan@suse.com>,
	Jailhouse <jailhouse-dev@googlegroups.com>,
	Claudio Fontana <claudio.fontana@gmail.com>,
	Jan Kiszka <jan.kiszka@siemens.com>,
	Markus Armbruster <armbru@redhat.com>,
	qemu-devel <qemu-devel@nongnu.org>,
	Hannes Reinecke <hare@suse.de>,
	Stefan Hajnoczi <stefanha@redhat.com>
Subject: Re: [RFC][PATCH 2/3] docs/specs: Add specification of ivshmem device revision 2
Date: Mon, 11 Nov 2019 15:27:43 +0000	[thread overview]
Message-ID: <20191111152743.GM814211@redhat.com> (raw)
In-Reply-To: <20191111100607-mutt-send-email-mst@kernel.org>

On Mon, Nov 11, 2019 at 10:08:20AM -0500, Michael S. Tsirkin wrote:
> On Mon, Nov 11, 2019 at 02:59:07PM +0100, Jan Kiszka wrote:
> > On 11.11.19 14:45, Michael S. Tsirkin wrote:
> > > On Mon, Nov 11, 2019 at 01:57:11PM +0100, Jan Kiszka wrote:
> > > > +| Offset | Register               | Content                                              |
> > > > +|-------:|:-----------------------|:-----------------------------------------------------|
> > > > +|    00h | Vendor ID              | 1AF4h                                                |
> > > > +|    02h | Device ID              | 1110h                                                |
> > > 
> > > Given it's a virtio vendor ID, please reserve a device ID
> > > with the virtio TC.
> > 
> > Yeah, QEMU's IVSHMEM was always using that. I'm happy to make this finally
> > official.
> > 
> 
> And I guess we will just mark it reserved or something right?
> Since at least IVSHMEM 1 isn't a virtio device.
> And will you be reusing same ID for IVSHMEM 2 or a new one?

1110h isn't under either of the virtio PCI device ID allowed ranges
according to the spec:

  "Any PCI device with PCI Vendor ID 0x1AF4, and PCI Device
   ID 0x1000 through 0x107F inclusive is a virtio device.
   ...
   Additionally, devices MAY utilize a Transitional PCI Device 
   ID range, 0x1000 to 0x103F depending on the device type. "

So there's no need to reserve 0x1110h from the virtio spec POV.

I have, however, ensured it is assigned to ivshmem from POV of
Red Hat's own internal tracking of allocated device IDs, under
its vendor ID.

If ivshmem 2 is now a virtio device, then it is a good thing that
it will get a new/different PCI device ID, to show that it is not
compatible with the old device impl.

Regards,
Daniel
-- 
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