[Qemu-devel] Re: [PATCH] Seabios irq override v3

[Jes Sorensen <jes@sgi.com>]

On 07/30/2009 01:27 AM, Kevin O'Connor wrote:
> I made some cleanups and committed a modified patch.
>
> I'd like to see what the dynamic irq0override code looks like.  The
> kvm on my machine is a little older and it fails when irq0override is
> set.
>
> Also, there is a set of irq overrides in the acpi madt code for kvm
> that set irq 5,9,10,11 to level triggered interrupts.  I don't see
> this in the latest kvm - can this now be removed?

Hi Kevin,

I justed tested your version and it works fine here. If I got some of
the formatting wrong, please let me know and I'll try to get it right
in the next set.

The tricky part with the irqoverride is that it is used by recent KVM,
but not older versions. qemu-kvm has a fw_cfg flag it uses to set (and
not set it when it detects an older version of KVM), however upstream
QEMU relies on the irqoverride unconditionally.

As the BIOS cannot detect which version of KVM it is running on, there
are two options, either we port the irqoverride fw_cfg to upstream QEMU,
or accept that Seabios will not work on older versions of KVM. I don't
think Anthony is super excited about adding this to upstream QEMU since
it is for legacy support, and I don't anticipate any distros starting
to ship Seabios with older version of KVM. I think it would be simpler
to just accept it won't work with the older KVM.

I thought about how to best do the dynamic override thing, and I think
the best thing is to just set it when we detect we are running on QEMU,
be it QEMU, KVM, or KQEMU. I have a patch that allows me to remove all
instances of CONFIG_KVM in Seabios, by using a new fw_cfg that tells the
bios what emulator it is running on. It would be interesting to see if
we could come up with a way for Coreboot to flag as well, so we can
share a single BIOS binary.

For the MADT stuff, I really don't know. Maybe Avi or Anthony can
comment?

I will post this patch shortly, I just need to make a few more minor
tweaks to it.

Cheers,
Jes