Messages in this thread | | | Date | Mon, 20 Feb 2012 09:10:45 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH][GIT PULL][v3.3] x86: Test saved %rip in NMI to determine nested NMI |
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* Steven Rostedt <rostedt@goodmis.org> wrote:
> On Sun, 2012-02-19 at 13:56 +0100, Ingo Molnar wrote: > > * Steven Rostedt <rostedt@goodmis.org> wrote: > > > > > Ingo, > > > > > > I found that it is possible for userspace to prevent an NMI > > > from triggering while it is running by setting its stack > > > pointer to that of the NMI stack. This tricks the NMI nested > > > algorithm in thinking that the NMI is nested. The easy > > > solution to this is to test the %rip to make sure that the NMI > > > happened in kernel mode before testing for nesting. > > > > Ouch... > > Note, it does not seem to cause any destruction, but screw up > profiling.
Except if the source of the NMI was not profiling, right?
Thanks,
Ingo
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