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Date: Mon, 14 Dec 2015 09:36:25 +0100
From: Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCHV2 3/3] x86, ras: Add mcsafe_memcpy() function to recover
 from machine checks
Message-ID: <20151214083625.GA28073@gmail.com>
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To: Andy Lutomirski <luto@amacapital.net>
Cc: "Luck, Tony" <tony.luck@intel.com>, "Williams, Dan J" <dan.j.williams@intel.com>, Borislav Petkov <bp@alien8.de>, Andrew Morton <akpm@linux-foundation.org>, Andy Lutomirski <luto@kernel.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "linux-mm@kvack.org" <linux-mm@kvack.org>, linux-nvdimm <linux-nvdimm@ml01.01.org>, X86 ML <x86@kernel.org>


* Andy Lutomirski <luto@amacapital.net> wrote:

> I still think it would be better if you get rid of BIT(63) and use a
> pair of landing pads, though.  They could be as simple as:
> 
> .Lpage_fault_goes_here:
>     xorq %rax, %rax
>     jmp .Lbad
> 
> .Lmce_goes_here:
>     /* set high bit of rax or whatever */
>     /* fall through */
> 
> .Lbad:
>     /* deal with it */
> 
> That way the magic is isolated to the function that needs the magic.

Seconded - this is the usual pattern we use in all assembly functions.

Thanks,

	Ingo

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