[SeaBIOS] RFC: Add support for virt machine to Seabios

[Rob Bradford]

Hi Gerd, thanks for you prompt reply,

On Fri, 2018-11-30 at 14:48 +0100, Gerd Hoffmann wrote:
> On Thu, Nov 29, 2018 at 05:37:41PM +0000, Rob Bradford wrote:
> > The virt machine in the NEMU project has the ambition to be a
> > platform
> > that has no emulated legacy hardware. This patch series enables
> > support
> > for that machine type in Seabios.
> 
> What exactly does "no legacy hardware" mean?  Does that include lpc
> devices such as pit and pic?
> 

That is correct, the host Linux kernel does provide some emulation of
devices as part of KVM though.

> What will seabios use as time source with -M virt?
> Seems there is no pmtimer ...
> 

That is correct. There does not appear to negative side effects with
lack of a time source when running Seabios against virt

(In the OVMF port I implement MicroSleep/NanoSleep with a KVM pvclock
and TSC based solution but i'm currently evaluating if this can be a
no-op as sleeping in a firmware is usually part of programming physical
hardware which is something that is not required with the virt machine
type.)

> > The impact that this has for a Seabios port is that the CMOS is not
> > available to query details of CPUs or memory configuration; instead
> > this
> > patch series modifies the code that queries those details to prefer
> > those from QEMU FW CFG over CMOS.
> 
> Doing that makes sense anyway, I'd say these three patches can be
> merged.  The other two should wait until the qemu patches are merged,
> to be sure the pci ids are the final ones.
> 

This PCI ID (0x8086 / 0x0d57) is from our internal registry which is
allocated exclusively for the use of the PCI host bridge on the virt
platform.

> cheers,
>   Gerd
> 

Cheers,

Rob