linux-kernel - Re: [RFC] x86_64: A real proposal for iret-less return to kernel

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Message-ID: <CALCETrWY4OW0FF3vsS+ntALU_kmmcEB9wf0RMg-H5kSO7jQ-wQ@mail.gmail.com>
Date:	Wed, 21 May 2014 15:20:50 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Borislav Petkov <bp@...en8.de>
Cc:	"Luck, Tony" <tony.luck@...el.com>, Jiri Kosina <jkosina@...e.cz>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Andi Kleen <andi@...stfloor.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>
Subject: Re: [RFC] x86_64: A real proposal for iret-less return to kernel

On Wed, May 21, 2014 at 3:17 PM, Borislav Petkov <bp@...en8.de> wrote:
> On Wed, May 21, 2014 at 03:13:16PM -0700, Andy Lutomirski wrote:
>> Why is this necessary?
>>
>> If the MCE hit kernel code, then we're going to die anyway.  If the
>> MCE hit user code, then we should be in a completely sensible context
>> and we can just send the signal.
>
> Are we guaranteed that the first thing the process will execute when
> scheduled back in are the signal handlers?

It's not even scheduled out, right?  This should be just like a signal
from a failed page fault, I think.

>
> And besides, maybe we don't even want to allow to do the switch_to() but
> kill it while it is sleeping.

What switch_to?

--Andy
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