Re: Out-of-Process Device Emulation session at KVM Forum 2020

[Michael S. Tsirkin]

On Wed, Nov 04, 2020 at 07:50:52AM +0100, Gerd Hoffmann wrote:
>   Hi,
> 
> > > I think not. Obviously each firmware should have its own ABI no matter
> > > whether its public or proprietary. For proprietary firmware, it should
> > > be understood by the proprietary userspace counterpart.
> > 
> > Userspace does not necessarily need to interpret the contents. The
> > vendor can ship a binary blob and the driver loads the file onto the
> > device without interpreting it.
> 
> Exactly.  Neither userspace nor kernel look at the blob, except maybe
> some headers with version, size, checksum etc.  Only the device does
> something with the actual content.
> 
> Doing the same make sense for migration device state.  The kernel driver
> saves and restores the device state.  Userspace doesn't need to look at
> it.  Again, with an exception for some header fields.
> 
> So requiring userspace being able to interpret the migration data
> (except header) for all devices looks rather pointless to me.

If nothing else we need a good place where vendors can publish this
data.

> Speaking of headers: Defining a common header format makes sense.
> For standard devices (virtio, nvme, ...) it makes sense to try define
> a standard, cross-vendor migration data format.
> For vendor-specific devices (gpus for example) I absolutely don't see
> the point.
> 
> take care,
>   Gerd