Messages in this thread | | | Date | Mon, 15 Jun 2009 11:55:16 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [tip:perfcounters/core] perf_counter: x86: Fix call-chain support to use NMI-safe methods |
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Ingo Molnar wrote: >>> >> I wouldn't actually expect that, *as long as* there is >> serialization between the cr2 write and the cr2 read. > > Well, is there any OS that heavily relies on cr2 writes and which > uses them from NMI context, and which CPU makers care about? > (Meaning: Windows, pretty much.) > > If not then i agree that in theory it should work fine, but in > practice we only know that we dont know the unknown risk here ;-) >
I think you can drop "uses them from NMI context" from that statement; writing to %cr2 is independent of the context.
I can try to find out internally what Intel's position on writing %cr2 is, but it'll take a while; however, KVM should be able to tell you if any random OS uses %cr2 writes (as should a static disassembly of their kernel.)
-hpa
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