linux-kernel - Re: [PATCH v2] x86: Return to kernel without IRET

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Message-ID: <82c35a60-0c7e-4e17-896e-8094d10df689@email.android.com>
Date:	Sat, 03 May 2014 19:14:07 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andy Lutomirski <luto@...capital.net>
CC:	Steven Rostedt <rostedt@...dmis.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	X86 ML <x86@...nel.org>, Gleb Natapov <gleb@...nel.org>,
	Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH v2] x86: Return to kernel without IRET

Not for return from NMIs themselves, to be sure

On May 3, 2014 4:51:37 PM PDT, Andy Lutomirski <luto@...capital.net> wrote:
>On Sat, May 3, 2014 at 3:19 PM, H. Peter Anvin <hpa@...or.com> wrote:
>> On 05/03/2014 04:24 AM, Steven Rostedt wrote:
>>> On Fri, 02 May 2014 21:03:10 -0700
>>> "H. Peter Anvin" <hpa@...or.com> wrote:
>>>
>>>>
>>>> I'd really like to see a workload which would genuinely benefit
>before
>>>> adding more complexity.  Now... if we can determine that it doesn't
>harm
>>>> anything and would solve the NMI nesting problem cleaner than the
>>>> current solution, that would justify things, too...
>>>>
>>>
>>> As I stated before. It doesn't solve the NMI nesting problem. It
>only
>>> handles page faults. We would have to implement this for breakpoint
>>> return paths too. Is that a plan as well?
>>>
>>
>> I would assume we would do it for *ALL* the IRETs.  There are only
>three
>> IRETs in the kernel last I checked...
>
>I think we should carefully avoid doing it for returns from NMI, though
>:)
>
>If you want a realistic benchmark that will speed up, packet
>forwarding might be a good place to look.
>
>--Andy

-- 
Sent from my mobile phone.  Please pardon brevity and lack of formatting.
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