linux-kernel - Re: [Qemu-devel] [Patch V2 1/2] x86, mce: Basic support to add LMCE support to QEMU

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Date:	Mon, 14 Dec 2015 16:32:14 -0200
From:	Eduardo Habkost <ehabkost@...hat.com>
To:	"Raj, Ashok" <ashok.raj@...el.com>
Cc:	Borislav Petkov <bp@...e.de>, kvm@...r.kernel.org,
	Tony Luck <tony.luck@...el.com>,
	Gong Chen <gong.chen@...el.com>,
	Gleb Natapov <gleb@...nel.org>, linux-kernel@...r.kernel.org,
	qemu-devel@...gnu.org, Andi Kleen <andi.kleen@...el.com>,
	Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [Qemu-devel] [Patch V2 1/2] x86, mce: Basic support to add LMCE
 support to QEMU

On Mon, Dec 14, 2015 at 02:11:46PM -0500, Raj, Ashok wrote:
> On Mon, Dec 14, 2015 at 05:37:38PM +0100, Borislav Petkov wrote:
> > 
> > ... and obviously LMCE is vendor-specific so it cannot be enabled on
> > !Intel guests with a define like that. mce_init() in qemu should check
> > vendor too.
> > 
> > The same mistake was done with SER_P but that's much harder to change,
> > as we discussed previously.
> > 
> 
> This is mostly harmless.. since the MCG_CAP space is shared and has no
> conflict between vendors. Also just the CAP being set has no effect.
> 
> The Guest OS needs to opt-in and the SIGBUS indicating SRAR are the only 
> ones that are treated special treatment. Also Intel was the only one
> broadcasting MCE's.. so we are like the rest now :-)

If the feature won't be enabled by default, I believe it will be
OK to not make it conditional on CPUID vendor (as we would be
simply doing that the user asked for).

But if it's going to be enabled by default, I would like to get
some assurance that there won't be conflicts between vendors in
the MCG_CAP bits.

-- 
Eduardo
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