Re: [patch 2/2] x86 NMI-safe INT3 and Page Fault

[Avi Kivity]

On 07/16/2010 09:05 PM, H. Peter Anvin wrote:
> > Module loading can certainly take a vmalloc_sync_all() (though I agree
> > it's unpleasant).  Anything else?
> >
> > Note perf is not modular at this time, but could be made so with
> > preempt/sched notifiers to hook the context switch.
> >
> >      
> Actually, module loading is already a performance problem; a lot of
> distros load sometimes hundreds of modules on startup, and it's heavily
> serialized, so I can see this being desirable to skip.
>    

There aren't that many processes at this time (or there shouldn't be, 
don't know how fork-happy udev is at this stage), so the sync should be 
pretty fast.  In any case, we can sync only modules that contain NMI 
handlers.

> I really hope noone ever gets the idea of touching user space from an
> NMI handler, though, and expecting it to work...
>    

I think the concern here is about an NMI handler's code running in 
vmalloc space, or is it something else?

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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