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

[Andy Lutomirski]

On Sat, May 3, 2014 at 3:19 PM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
> On 05/03/2014 04:24 AM, Steven Rostedt wrote:
>> On Fri, 02 May 2014 21:03:10 -0700
>> "H. Peter Anvin" <hpa@xxxxxxxxx> 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
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