Re: [Xen-devel] [PATCH v2 1/4] xen/libxc: Allow changes to hypervisor CPUID leaf from config file

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 11.03.14 at 04:54, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> wrote:
> Currently only "real" cpuid leaves can be overwritten by users via
> 'cpuid' option in the configuration file. This patch provides ability to
> do the same for hypervisor leaves (those in the 0x40000000 range).

And honestly I'm not certain we want to go that far. Limiting the
number of leaves seems reasonable (even CPU vendors had to
introduce this), but altering other hypervisor CPUID output seems
to only call for trouble.

> +struct xen_sysctl_cpuid {
> +     uint32_t input[2];
> +     uint32_t eax;
> +     uint32_t ebx;
> +     uint32_t ecx;
> +     uint32_t edx;
> +};

Having just the four register fields here would be enough - eax
and ecx would simply be IN/OUT (and if need be in the future,
ebx/edx could become IN/OUT too without altering the structure
layout).

Jan


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