Re: [Xen-devel] [PATCH] Fix etherboot option ROM loading

[Gianni Tedesco <gianni.tedesco@xxxxxxxxxx>]

On Mon, 2010-06-28 at 19:57 +0100, Keir Fraser wrote:
> On 28/06/2010 19:07, "Gianni Tedesco" <gianni.tedesco@xxxxxxxxxx> wrote:
> 
> > I am working on improved fix for this by building a gPXE ROM with
> > support for both rtl8139 and e1000
> 
> Which is what we do already, right? Or do we actually end up with two
> separate ROMs, one for rtl8139 and one for e1000?

No there's two separate ROM's. When I installed the rtl8139 ROM on an
e1000 machine it didn't recognize any network devices. That's what
prompted me to this patch.

And as for fixing for one kind of e1000 and breaking for other cases we
care about, I'm afraid that the answer is "yes we are." At least
assuming other qemu's out there with different PCI ID's?

> Hm, anyway, presumably internally gpxe has a list of vendor_id:device_id
> pairs for each NIC type that it supports? Shouldn't we just patch it so that
> the entire list gets exposed in the option ROM headers? That seems the
> simple straightforward fix, or is it more complex than that?

Yeah, I mean, if we load a ROM for e1000, then all types of e1000 will
work but the problem is that I'm not sure how we can get a list in to
the ROM headers. The spec was designed for loading a ROM from a specific
card. If we simply ignore the PCI ID's in the ROM header and load the
first blob then we may end up loading rtl8139 on e1000 machines or vice
versa just based on which ROM comes first... 

I suppose we could use a custom protocol to export a list of ID's for a
ROM. I would suggest a header that goes before the ROM so as not to
interfere with the standards-conforming bits. We'd just have to
special-case ethernet ROM handling a bit more in hvmloader.

Ideally we want 1 ROM with support for both chipsets and therefore all
known variants of those chipsets. That would allow for HVM's with card
of multiple types. But not figured out how to get gPXE to play like that
yet.

> -- Keir

Gianni


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