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From: Borislav Petkov <bp@alien8.de>
To: Mathieu Chouquet-Stringer <me@mathieu.digital>
Cc: Matthew Garrett <mjg59@google.com>,
	Chris Down <chris@chrisdown.name>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	sean.j.christopherson@intel.com, tony.luck@intel.com,
	Linus Torvalds <torvalds@linux-foundation.org>,
	the arch/x86 maintainers <x86@kernel.org>,
	kernel-team@fb.com
Subject: Re: [PATCH -v2.1] x86/msr: Filter MSR writes
Date: Tue, 17 Nov 2020 22:20:16 +0100	[thread overview]
Message-ID: <20201117212016.GQ5719@zn.tnic> (raw)
In-Reply-To: <20201117210018.GA4247@weirdfishes>

On Tue, Nov 17, 2020 at 10:00:18PM +0100, Mathieu Chouquet-Stringer wrote:
> I'm late to the party but it seems allowing MSR_IA32_ENERGY_PERF_BIAS
> has the downside of flagging the kernel as tainted without telling you
> why if you use something like x86_energy_perf_policy (from
> tools/power/x86/x86_energy_perf_policy) which itself is used by tuned.

Not for long:

https://git.kernel.org/tip/fe0a5788624c8b8f113a35bbe4636e37f9321241

> So while both documentation and tools should be updated as to be clearer
> and to not taint the kernel respectively, there's something that remains
> to be done to explain why or how the kernel got tainted because of
> poking into MSRs...

Because if you poke at random MSRs and you manage to "configure" your
CPU to run "out of spec" - this is what the taint flag is called:
TAINT_CPU_OUT_OF_SPEC - then this is exactly the case you've created: a
CPU executing outside of specifications.

I agree with the update-the-documentation aspect - S does not mean only
SMP kernel on !SMP-capable CPU but the more general, CPU is out of spec.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

  reply	other threads:[~2020-11-17 21:20 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-12 10:50 [RFC PATCH] x86/msr: Filter MSR writes Borislav Petkov
2020-06-12 16:34 ` Sean Christopherson
2020-06-12 16:46   ` Borislav Petkov
2020-06-12 16:57     ` Sean Christopherson
2020-06-12 17:03       ` Borislav Petkov
2020-06-12 17:43         ` Sean Christopherson
2020-06-12 17:52           ` Borislav Petkov
2020-06-12 17:20 ` Linus Torvalds
2020-06-12 17:48   ` Borislav Petkov
2020-06-12 19:47     ` Borislav Petkov
2020-06-12 20:39     ` Peter Zijlstra
2020-06-13  5:40       ` Tony Luck
2020-06-13  9:39       ` Borislav Petkov
2020-06-13 15:48 ` [PATCH -v2] " Borislav Petkov
2020-06-15  6:38   ` [PATCH -v2.1] " Borislav Petkov
2020-06-25  5:51     ` Sean Christopherson
2020-06-25  8:37       ` Borislav Petkov
2020-07-14 12:19     ` Chris Down
2020-07-14 15:47       ` Borislav Petkov
2020-07-14 16:04         ` Chris Down
2020-07-14 16:46           ` Luck, Tony
2020-07-14 16:58             ` Borislav Petkov
2020-07-14 17:02             ` Chris Down
2020-07-14 16:56           ` Borislav Petkov
2020-07-14 17:04             ` Chris Down
2020-07-14 18:52             ` Srinivas Pandruvada
2020-07-15  4:26               ` Borislav Petkov
2020-07-14 19:17           ` Matthew Garrett
2020-11-17 21:00             ` Mathieu Chouquet-Stringer
2020-11-17 21:20               ` Borislav Petkov [this message]
2020-11-18  8:58                 ` Mathieu Chouquet-Stringer
2020-11-18  9:09                 ` Mathieu Chouquet-Stringer
2020-11-18 11:50                   ` Borislav Petkov
2020-11-18 14:04                     ` [PATCH] " Mathieu Chouquet-Stringer
2020-11-18 17:50                       ` Borislav Petkov
2020-11-19 10:53                         ` Mathieu Chouquet-Stringer
2020-11-25 21:41                           ` Mathieu Chouquet-Stringer
2020-11-26 10:03                           ` Borislav Petkov
2020-11-17 21:21               ` [PATCH -v2.1] " Matthew Garrett
2020-11-17 21:22                 ` Matthew Garrett
2020-11-18  9:02                   ` Mathieu Chouquet-Stringer
2020-06-17 15:06 ` [tip: x86/misc] " tip-bot2 for Borislav Petkov
2020-06-25  8:45 ` tip-bot2 for Borislav Petkov

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