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

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Date:	Tue, 25 Nov 2014 19:24:10 +0100
From:	Borislav Petkov <bp@...e.de>
To:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Richard Hendershot <rshendershot@...si.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.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 01:12:10PM -0500, Boris Ostrovsky wrote:
> On 11/19/2014 03:52 PM, Greg Kroah-Hartman wrote:
> >3.17-stable review patch.  If anyone has any objections, please let me know.
> 
> 
> This breaks PV on Xen.
> 
> -boris
> 
> >
> >------------------
> >
> >From: Borislav Petkov <bp@...e.de>
> >
> >commit 85be07c32496dc264661308e4d9d4e9ccaff8072 upstream.
> >
> >We should be accessing it through a pointer, like on the BSP.
> >
> >Tested-by: Richard Hendershot <rshendershot@...si.com>
> >Fixes: 65cef1311d5d ("x86, microcode: Add a disable chicken bit")
> >Signed-off-by: Borislav Petkov <bp@...e.de>
> >Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> >
> >---
> >  arch/x86/kernel/cpu/microcode/core_early.c |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> >--- a/arch/x86/kernel/cpu/microcode/core_early.c
> >+++ b/arch/x86/kernel/cpu/microcode/core_early.c
> >@@ -124,7 +124,7 @@ void __init load_ucode_bsp(void)
> >  static bool check_loader_disabled_ap(void)
> >  {
> >  #ifdef CONFIG_X86_32
> >-	return __pa_nodebug(dis_ucode_ldr);
> >+	return *((bool *)__pa_nodebug(&dis_ucode_ldr));

And practically the same line in check_loader_disabled_bsp() doesn't?

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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