linux-kernel - Re: [Xen-devel] PROBLEM: kernel panic xsave

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Date:	Tue, 20 Oct 2015 08:41:02 -0600
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"Boris Ostrovsky" <boris.ostrovsky@...cle.com>
Cc:	"John Doe" <securef33d@...il.com>,
	"Ingo Molnar" <mingo@...nel.org>, <x86@...nel.org>,
	<xen-devel@...ts.xen.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [Xen-devel] PROBLEM: kernel panic xsave_init

>>> On 20.10.15 at 16:27, <boris.ostrovsky@...cle.com> wrote:
> On 10/20/2015 09:43 AM, Jan Beulich wrote:
>>>>> On 20.10.15 at 15:22, <boris.ostrovsky@...cle.com> wrote:
>>> The reason I think its this commit is that RAX, RDX and RCX look very
>>> much like arguments to xsetbv (which xstate_enable_boot_cpu() executes)
>>> and RAX value is 0x1f, which has two new bits that this commit defined.
>> That would be the two MPX related bits, yet us (luckily) white listing
>> leaf 7 in pv_cpuid(), it is quite easy to validate that we don't expose
>> this feature to PV(H) guests.
> 
> Oh, so something like
> 
> cpuid=['0x7:ebx=xxxxxxxxxxxxxxxxx0xxxxxxxxxxxxxx']
> 
> (bit 14 as zero) for John to try then.

He might try it, but as per what I've said this shouldn't make a
difference for PV(H) guests.

Jan

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