Re: [patch 1/2] x86_64 page fault NMI-safe

[Andi Kleen]

On Thu, Jul 15, 2010 at 04:23:20PM -0700, Linus Torvalds wrote:
> On Thu, Jul 15, 2010 at 4:20 PM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
> > On 07/15/2010 03:58 PM, Andi Kleen wrote:
> >>> Why do we force IST use for NMI, btw? Maybe we shouldn't, and just use
> >>> the normal kernel stack mechanisms?
> >>
> >> If you don't use IST the SYSCALL entry is racy during the window
> >> when RSP is not set up yet (same for MCE etc.)
> >>
> >
> > Right, the kernel stack is not ready.
> 
> Well, it may not be ready for the _current_ NMI handler, but if we're
> going to do a stack switch in sw on NMI anyway... ?

The CPU written initial stack frame would still go on the wrong stack.

-Andi

-- 
ak@xxxxxxxxxxxxxxx -- Speaking for myself only.
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