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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 30.05.12 at 20:17, Borislav Petkov <bp@xxxxxxxxx> 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).

Jan


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