linux-kernel - Re: [tip:x86/efi] x86/efi: Check for unsafe dealing with FPU state in irq ctxt

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Message-ID: <538F9AFA.5050806@zytor.com>
Date:	Wed, 04 Jun 2014 15:17:30 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	linux-kernel@...r.kernel.org, mingo@...nel.org,
	ricardo.neri-calderon@...ux.intel.com, tglx@...utronix.de,
	bp@...e.de, matt.fleming@...el.com,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/efi] x86/efi: Check for unsafe dealing with FPU state
 in irq ctxt

On 06/04/2014 03:15 PM, tip-bot for Borislav Petkov wrote:
> Commit-ID:  baa916f39b50ad91661534652110df40396acda0
> Gitweb:     http://git.kernel.org/tip/baa916f39b50ad91661534652110df40396acda0
> Author:     Borislav Petkov <bp@...e.de>
> AuthorDate: Fri, 25 Apr 2014 13:40:10 +0200
> Committer:  Matt Fleming <matt.fleming@...el.com>
> CommitDate: Sat, 3 May 2014 06:39:25 +0100
> 
> x86/efi: Check for unsafe dealing with FPU state in irq ctxt
> 
> efi_call can happen in an irq context (pstore) and there we really need
> to make sure we're not scribbling over FPU state while we've interrupted
> a thread or kernel mode with a live FPU state. Therefore, use the
> kernel_fpu_begin/end() variants which do that check.
> 
> Signed-off-by: Borislav Petkov <bp@...e.de>
> Cc: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
> Signed-off-by: Matt Fleming <matt.fleming@...el.com>
> ---
>  arch/x86/include/asm/efi.h | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 

I seem to have lost track of this... does this actually solve anything,
or does it just mean we'll explode hard?

	-hpa


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