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Subject: Re: [Xen-devel] [PATCH v2 3/3] paravirt: rename paravirt_enabled to
 paravirt_legacy
To: Borislav Petkov <bp@alien8.de>, Andrew Cooper <andrew.cooper3@citrix.com>
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From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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Date: Mon, 8 Feb 2016 11:52:51 -0500
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On 02/08/2016 11:45 AM, Borislav Petkov wrote:
> On Mon, Feb 08, 2016 at 04:38:40PM +0000, Andrew Cooper wrote:
>> Does the early loader have extable support?  If so, this is fairly easy
>> to fix.  If not, we have a problem.
> It doesn't and regardless, you want to have this CPUID querying as
> simple as possible. No special handling, no special prefixes as it
> should be able to run on other hypervisors too.
>
> If one can't execute a simple CPUID(0x4...) on a xen guest and get the
> results back, then for early, we will have to do what we've done until
> now and simply emulate the MSR accesses.

I think xen_hypervisor check can be done in microcode_init() as this is 
first time PV kernel deals with microcode.

Let me try it --- I want to see what happens on hotplug and resume but I 
am reasonably certain this should work during boot.

-boris

>
> Later code can use then xen_cpuid() and all is fine. We should still get
> rid of paravirt_enabled() though.
>