Re: [Xen-devel] [PATCH v3 08/28] xen/x86: Annotate VM applicability in featureset

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 15.03.16 at 16:35, <andrew.cooper3@xxxxxxxxxx> wrote:
> v3:
>  * Rebase over the new namespaceing changes.
>  * Expand commit message.
>  * Correct PSE36 to being a HAP-only feature.

As Tim has pointed out on IRC, this may need revisiting.

> +XEN_CPUFEATURE(MCE,           0*32+ 7) /*A  Machine Check Architecture */

Exposing MCA makes sense, but do we really need to expose MCE
too?

> +XEN_CPUFEATURE(MTRR,          0*32+12) /*S  Memory Type Range Registers */

I thin I've said so before - this alters current behavior, and is pretty
certainly wrong for PV Dom0.

>  XEN_CPUFEATURE(DS,            0*32+21) /*   Debug Store */

Is leaving this unexposed compatible with vPMU (would then
presumably also apply to DTES64 and DSCPL)?

> +XEN_CPUFEATURE(X2APIC,        1*32+21) /*A  Extended xAPIC */

Does this make sense for PV?

> +XEN_CPUFEATURE(HYPERVISOR,    1*32+31) /*A  Running under some hypervisor */

Wouldn't this better be one of the special ones?

> +XEN_CPUFEATURE(LM,            2*32+29) /*A  Long Mode (x86-64) */

I think I had asked before, but doesn't the customization needed
for 32-bit PV guests also rather make this a special one? Or if not,
perhaps the commit message could be made say a word on the
intention regarding runtime overrides to these statically determine
sets?

> +XEN_CPUFEATURE(LWP,           3*32+15) /*A  Light Weight Profiling */

Right now this gets cleared by pv_cpuid(), so I think this needs to
be S.

Jan


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