Re: [Xen-devel] tools/libxc/xc_cpuid_x86.c:cpuid()'s inline asm

[Keir Fraser <keir.xen@xxxxxxxxx>]

On 02/12/2011 08:54, "Jan Beulich" <JBeulich@xxxxxxxx> wrote:

> Keir,
> 
> do you recall what it was that 20976:f8692cc67d67 was supposed to fix?
> The code is clearly wrong now on x86-64 - inline asm that uses push/pop
> (or other stack pointer manipulation instructions) and memory accesses
> that may reference the stack (even if not through %rsp) can't be
> expected to work without -mno-red-zone.

I totally missed the red-zone constraint. :-(

> The question is whether to use that command line option, or whether to
> correct the inline assembly (besides the purpose of your change, I also
> wonder why this isn't coded the obvious way, with rBX and rDX explicitly
> named in the constraints - on 32-bit this may be to reduce register
> pressure, but on 64-bit it's entirely unclear).

I think reg constraint failures had only been reported on 32-bit. So how
about the attached patch?

 -- Keir

> Thanks, Jan
>

Attachment: 00-cpuid-asm
Description: Binary data

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel