From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: Getting the XSAVE size from userspace
Date: Thu, 5 Nov 2015 10:49:33 +0000
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To: Razvan Cojocaru <rcojocaru@bitdefender.com>
Cc: Jan Beulich <JBeulich@suse.com>, "xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
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On 05/11/15 10:42, Jan Beulich wrote:
>>>> On 05.11.15 at 10:52, <rcojocaru@bitdefender.com> 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