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

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Date:	Tue, 25 Nov 2014 13:12:10 -0500
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org
CC:	stable@...r.kernel.org,
	Richard Hendershot <rshendershot@...si.com>,
	Borislav Petkov <bp@...e.de>,
	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 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));
>   #else
>   	return dis_ucode_ldr;
>   #endif
>
>
> --
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