[virtio-dev] Re: [virtio-comment] [PATCH 00/11] Introduce transitional mmr pci device

Stefan Hajnoczi
2023-04-03T19:10:25Z

[-- Attachment #1: Type: text/plain, Size: 1110 bytes --]

On Mon, Apr 03, 2023 at 10:53:29AM -0400, Parav Pandit wrote:
>
>
> On 4/3/2023 10:45 AM, Stefan Hajnoczi wrote:
> > On Fri, Mar 31, 2023 at 01:58:23AM +0300, Parav Pandit wrote:
> > > Overview:
> > > ---------
> > > The Transitional MMR device is a variant of the transitional PCI device.
> >
> > What does "MMR" mean?
> >
> memory mapped registers.
> Explained below in the design section and also in relevant patches 6 to 11.

Maybe call it "Memory-mapped Transitional"? That name would be easier to
understand.

> > Modern devices were added to Linux in 2014 and support SR-IOV.
>
> > Why is it
> > important to support Transitional (which really means Legacy devices,
> > otherwise Modern devices would be sufficient)?
> >
> To support guest VMs which only understand legacy devices and unfortunately
> they are still in much wider use by the users.

I wonder which guest software without Modern VIRTIO support will still
be supported by the time Transitional MMR software and hardware becomes
available. Are you aiming for particular guest software versions?

Stefan

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]