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

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Date:	Tue, 20 Oct 2015 07:43:44 -0600
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"John Doe" <securef33d@...il.com>,
	"Boris Ostrovsky" <boris.ostrovsky@...cle.com>
Cc:	"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 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. Sadly the story is different for HVM
guests (where the leaf handling uses black listing), but the register
dump here clearly points to a PV guest (or Dom0).

Jan

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