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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.11.15 at 11:47, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
> On 11/05/2015 12:42 PM, 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?
> 
> That's because the userspace application doesn't live in dom0, but in a
> dedicated privileged domain, and I'm unsure if a CPUID issued there
> yields the same results as a CPUID issued in dom0. So I thought the
> safest way is to get the information directly from the hypervisor. Is
> this assumption incorrect?

See my other reply (to Andrew) - as long as there's no problem with
using the maximum possible size, I don't see why you couldn't use
just CPUID.

Jan


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