| From | Andi Kleen <> | Subject | Re: [patch 4/8] x86/tsc: Verify TSC_ADJUST from idle | Date | Mon, 21 Nov 2016 14:57:13 -0800 |
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Thomas Gleixner <tglx@linutronix.de> writes:
> 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.
idle entry is a time critical code path too, because idle periods are often very short. rdmsr is a us+ at least. You'll likely make workloads that do a lot of short sleeps noticeable slower.
If anything load limit it aggressively.
BTW I don't think this situation of SMM tampering with TSC is common anyways, so it may be simply not worth checking, or perhaps only with a debug boot option.
-Andi
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