[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <87k2bwxwza.fsf@tassilo.jf.intel.com>
Date: Mon, 21 Nov 2016 14:57:13 -0800
From: Andi Kleen <andi@...stfloor.org>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: LKML <linux-kernel@...r.kernel.org>,
Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
Borislav Petkov <bp@...en8.de>, Yinghai Lu <yinghai@...nel.org>
Subject: Re: [patch 4/8] x86/tsc: Verify TSC_ADJUST from idle
Thomas Gleixner <tglx@...utronix.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
Powered by blists - more mailing lists