Re: [Xen-devel] [PATCH RFC v1 40/74] xen/x86: report domain id on cpuid

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 04.01.18 at 14:05, <wei.liu2@xxxxxxxxxx> wrote:
> --- a/xen/include/public/arch-x86/cpuid.h
> +++ b/xen/include/public/arch-x86/cpuid.h
> @@ -57,7 +57,8 @@
>   * Leaf 2 (0x40000x01)
>   * EAX[31:16]: Xen major version.
>   * EAX[15: 0]: Xen minor version.
> - * EBX-EDX: Reserved (currently all zeroes).
> + * EBX: Domain id.
> + * ECX-EDX: Reserved (currently all zeroes).
>   */

There's one issue here, as I've noticed only now: How does a
caller distinguish domid being zero from the information not
being provided by an older hypervisor? I think there needs to
be a qualifying bit elsewhere.

Jan


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