linux-kernel - Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover from machine checks

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Date:	Sun, 27 Dec 2015 11:09:19 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Tony Luck <tony.luck@...il.com>,
	Andy Lutomirski <luto@...capital.net>
Cc:	linux-nvdimm <linux-nvdimm@...1.01.org>, X86 ML <x86@...nel.org>,
	"elliott@....com" <elliott@....com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Williams, Dan J" <dan.j.williams@...el.com>,
	Ingo Molnar <mingo@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover
 from machine checks

On Sat, Dec 26, 2015 at 10:57:26PM -0800, Tony Luck wrote:
> ... will get the right value.  Maybe this would still work out
> if the fixup is a 31-bit value plus a flag, but the external
> tool thinks it is a 32-bit value?  I'd have to ponder that.

I still fail to see why do we need to make it so complicated and can't
do something like:


fixup_exception:
	...

#ifdef CONFIG_MCE_KERNEL_RECOVERY
		if (regs->ip >= (unsigned long)__mcsafe_copy &&
		    regs->ip <= (unsigned long)__mcsafe_copy_end)
			run_special_handler();
#endif

and that special handler does all the stuff we want. And we pass
X86_TRAP* etc through fixup_exception along with whatever else we
need from the trap handler...

Hmmm?

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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