Re: [Xen-devel] [PATCH 0/3] x86/paravirt: Fix baremetal paravirt MSR ops
From: Andrew Cooper
Date: Thu Sep 17 2015 - 11:33:01 EST
On 17/09/15 16:27, Borislav Petkov wrote:
> On Thu, Sep 17, 2015 at 01:39:26PM +0200, Paolo Bonzini wrote:
>> That's not a big deal, that's what *_safe is for. The problem is that
>> there are definitely some cases where the *_safe version is not being used.
> I mean to do feature checks which assure you that those MSRs are
> there so you don't need the safe variants. And that is not always
> easy/possible.
>
There are plenty of non-architectural MSRs in use which don't have
feature bits.
Xen used to have problems booting when using the masking MSRs when
booting virtualised. Nowadays it uses a cpu vendor check and _safe()
probe to detect support.
~Andrew
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