Messages in this thread | | | From | Andi Kleen <> | Subject | Re: [PATCH UPDATE] x86: ignore spurious faults | Date | Fri, 25 Jan 2008 10:11:36 +0100 |
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On Friday 25 January 2008 09:38:38 Nick Piggin wrote: > On Friday 25 January 2008 19:15, Jan Beulich wrote: > > Actually, another thought: permitting (and handling) spurious faults for > > kernel mappings conflicts with NMI handling, i.e. great care would be > > needed to ensure the NMI path cannot touch any such mapping. So > > even the present Xen/Linux Dom0 implementation may have some > > (perhaps unlikely) problems here, and it would get worse if we added > > e.g. a virtual watchdog NMI (something I am considering, which would > > then extend the problem to DomU-s). > > Can you explain how they conflict?
NMI is blocked by the hardware until IRET and when a page fault happens inside the NMI handler the early IRET unblocks it and then NMIs can nest, which will lead to stack corruption.
-Andi
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