Re: [Xen-devel] Getting the XSAVE size from userspace

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 05/11/15 10:42, Jan Beulich wrote:
>>>> On 05.11.15 at 10:52, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
>> I need to get the XSAVE size from userspace. The easiest way seems to be
>> to use the XEN_DOMCTL_getvcpuextstate hypercall, but that hypercall is
>> not public / there's no xenctrl.h wrapper for it.
> Before going into any detail of the rest of your mail - any reason you
> can't just consult CPUID output?

It depends on precisely what you want.

CPUID.0xD[0].ecx gives you the maximum xsave area on this processor
CPUID.0xD[0].ebx gives you the current size for the value in xcr0, but
that is not very useful from userspace.

~Andrew

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