Messages in this thread | | | Date | Mon, 21 Nov 2016 09:16:44 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [patch 4/8] x86/tsc: Verify TSC_ADJUST from idle |
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On Sun, 20 Nov 2016, Peter Zijlstra wrote: > On Sat, Nov 19, 2016 at 01:47:37PM -0000, Thomas Gleixner wrote: > > When entering idle, it's a good oportunity to verify that the TSC_ADJUST > > MSR has not been tampered with (BIOS hiding SMM cycles). If tampering is > > detected, emit a warning and restore it to the previous value. > > > +++ b/arch/x86/kernel/process.c > > @@ -277,6 +277,7 @@ void exit_idle(void) > > > > void arch_cpu_idle_enter(void) > > { > > + tsc_verify_tsc_adjust(); > > local_touch_nmi(); > > enter_idle(); > > } > > Doing a RDMSR on the idle path isn't going to be popular. That path is > already way too slow.
Of course we can ratelimit that MSR read with jiffies, but do you have any better suggestion aside of doing it timer based?
Thanks,
tglx
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