Re: [RFC] QEMU KVM target -> Anthony

Anthony Liguori
2007-03-19T01:39:33Z

Dâniel Fraga wrote:
> On Sun, 18 Mar 2007 16:08:21 -0700
> "Ed Swierk" <eswierk-t4QvRbHP2kpBDgjK7y7TUQ@public.gmane.org> wrote:
>
>
>> Please read this email thread if you want to know why your assumption
>> is incorrect:
>> http://lists.gnu.org/archive/html/qemu-devel/2006-10/msg00175.html
>>
>
> I read everything. The last message by Paul Brook:
>
> "- qemu makes assumptions about the layout of the code gcc generates.
> This works by chance on older gcc. This effects all hosts, and is not a gcc bug.
>
> - qemu reserves several registers for its own use. On architecturally crippled
> hosts (ie. x86) this means we hit really obscure gcc bugs on x86 because gcc
> runs out of registers. This is a gcc bug, but is also relatively easy to
> workaround".
>
> He even proposes a solution:
>
> https://nowt.dyndns.org/
>
> And even this way, nobody agreed with each other...
>
> So I ask: if Paul Brook could fix this, why it isn't merged? A
> solution should be applied. What we can't do is keep discussing forever
> this and the previous message is realy annoying:
>

This is qops which is why I said "qops is the right solution" in my
previous note. It's a huge, fundamental change to QEMU so it needs some
time being developed outside of the main tree.

I understand that it's frustrating to depend on gcc3. Please realize
though that if it was simple to fix than it would be fixed and more
importantly, that the work is being done to fix the situation.

Regards,

Anthony Liguori

> "Basically, gcc changed in a way that broke qemu. There's been an open
> bug report in gcc ever since, but the GCC developers really aren't interested in
> backwards compatability. (Heck, gcc 4.0 breaks building bash 2.05b). The
> qemu developers aren't interested in applying ugly patches to support gcc 4.x
> until gcc 3.x becomes so obsolete nobody ships it anymore. (And considering
> that there are still some niche embedded boards that have hacked up versions
> of gcc 2.95 targeting them and nothing else, I wouldn't be surprised if in
> five years we have your main compiler and the compiler to build qemu, ala
> kgcc under Red Hat 7. *shrug*)"
>
> It's like saying: "we don't care. Keep using gcc3". :(