linux-kernel - Re: STI architectural question (and lretq -- I'm not even kidding)

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Date:	Wed, 23 Jul 2014 14:52:53 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Borislav Petkov <bp@...en8.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	X86 ML <x86@...nel.org>
Subject: Re: STI architectural question (and lretq -- I'm not even kidding)

On Wed, Jul 23, 2014 at 2:18 PM, Andi Kleen <andi@...stfloor.org> wrote:
> Andy Lutomirski <luto@...capital.net> writes:
>
>> I think an MCE just might be okay -- it's not
>> really recoverable anyway.
>
> That's wrong.

I think that, other than broadcast MCEs, #MC that hits in kernel mode
is non-recoverable, or at least can't safely be recovered.  (There's a
separate APIC interrupt for recoverable errors, I think, but that's a
much saner interface.)

Regardless, I put in a fixup in the patches I sent out -- they should
be just as safe as existing code if a #MC hits right after sti.  I
have no idea how to test that, though...

--Andy

>
> -Andi
>
> --
> ak@...ux.intel.com -- Speaking for myself only



-- 
Andy Lutomirski
AMA Capital Management, LLC
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