linux-kernel - Re: [PATCH 3.17 100/141] x86, microcode: Fix accessing dis_ucode

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Message-ID: <20141125203634.GA6433@laptop.dumpdata.com>
Date:	Tue, 25 Nov 2014 15:36:34 -0500
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Borislav Petkov <bp@...e.de>
Cc:	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Richard Hendershot <rshendershot@...si.com>,
	David Vrabel <david.vrabel@...rix.com>
Subject: Re: [PATCH 3.17 100/141] x86, microcode: Fix accessing dis_ucode_ldr
 on 32-bit

On Tue, Nov 25, 2014 at 09:26:28PM +0100, Borislav Petkov wrote:
> On Tue, Nov 25, 2014 at 02:28:46PM -0500, Boris Ostrovsky wrote:
> > You'd have to decide at runtime --- many baremetal systems are
> > compiled with PARAVIRT.
> 
> Right, but the microcode loader is not used at all on PV, right?

Is there an use-case for this in virtualization at all?
> 
> If so, I'd like to add a arch_something_blabla_disabled_loader()
> function which is run in the loader init path and returns false on
> baremetal and a true when running as a xen guest. I'm not sure how the
> detection should be done, though... CPUID with the hypervisor leaf?

Why not make it in general then? Like:

if (cpu_has_hypervisor)
	return;

?

> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> Sent from a fat crate under my desk. Formatting is fine.
> --
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