Re: [Xen-devel] [PATCH] x86/amd: fix crash as Xen Dom0 on AMD Trinity systems

[Borislav Petkov <bp@alien8.de>]

On Thu, May 31, 2012 at 08:39:15AM +0100, Jan Beulich wrote:
> >>> On 30.05.12 at 20:17, Borislav Petkov <bp@alien8.de> wrote:
> > On Wed, May 30, 2012 at 11:00:23AM -0700, H. Peter Anvin wrote:
> > The other place where we use the amd_safe variants is an obscure K8,
> > revC and earlier fix for _some_ BIOSen and this hasn't bitten us yet
> > so I'm assuming people haven't run xen on such boxes yet. Does it need
> > fixing? Probably, if we really really have to.
> 
> This again is something that shouldn't even be attempted under
> Xen. The hypervisor, unless really old, does this (and wouldn't
> allow the write by any domain - privileged or not - anyway).
> 
> There's one more user though - the code triggered by the
> "show_msr=" command line option. This one indeed requires
> rdmsr_safe_regs to be functional (albeit under Xen, once
> again, this won't work currently anyway for those MRS on
> old CPUs where the special key in %edi is required, which the
> emulation code in Xen doesn't support).

This doesn't look right. Yinghai, why does generic x86 code use
rdmsrl_amd_safe - it should simply use rdmsrl_safe.

-- 
Regards/Gruss,
Boris.