From: Borislav Petkov <bp@suse.de>
To: "Raj, Ashok" <ashok.raj@intel.com>
Cc: X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>, Tony Luck <tony.luck@intel.com>,
Andi Kleen <andi.kleen@intel.com>,
Tom Lendacky <thomas.lendacky@amd.com>,
Arjan Van De Ven <arjan.van.de.ven@intel.com>
Subject: Re: [v2 1/3] x86/microcode/intel: Check microcode revision before updating sibling threads
Date: Thu, 22 Feb 2018 13:15:06 +0100 [thread overview]
Message-ID: <20180222121506.GC27489@pd.tnic> (raw)
In-Reply-To: <20180222115554.GA3797@araj-mobl1.jf.intel.com>
On Thu, Feb 22, 2018 at 03:55:54AM -0800, Raj, Ashok wrote:
> The current code wasn't trying to enforce checking the loaded microcode revision on a thread
> before attempting to load the microcode. While you comeback from resume, if C0T0 already
> is up, and we loaded the early microcode, then when handling C0T1 there is no need to
> do a wrmsrl to reapply microcode since its already loaded as part of C0T0.
And I'm asking exactly this: is it simply "we don't need to do WRMSR" or
"we should not"?
Because avoiding the WRMSR costs more than simply doing it and letting
the HT thread ignore the supplied microcode.
If it is "we don't need to but there's nothing wrong when we do it" then
we don't need this patch. And I'm pretty sure "nothing wrong when we do
it" would be the answer. Otherwise we have bigger problems.
--
Regards/Gruss,
Boris.
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--
next prev parent reply other threads:[~2018-02-22 12:15 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-22 6:33 [v2 0/3] Patches to address some limitations in OS microcode loading Ashok Raj
2018-02-22 6:33 ` [v2 1/3] x86/microcode/intel: Check microcode revision before updating sibling threads Ashok Raj
2018-02-22 11:00 ` Borislav Petkov
2018-02-22 11:55 ` Raj, Ashok
2018-02-22 12:15 ` Borislav Petkov [this message]
2018-02-22 13:19 ` Raj, Ashok
2018-02-22 13:44 ` Borislav Petkov
2018-02-22 15:46 ` Henrique de Moraes Holschuh
2018-02-22 15:49 ` Van De Ven, Arjan
2018-02-22 17:51 ` Henrique de Moraes Holschuh
2018-02-22 6:33 ` [v2 2/3] x86/microcode/intel: Perform a cache flush before ucode update Ashok Raj
2018-02-22 6:33 ` [v2 3/3] x86/microcode: Quiesce all threads before a microcode update Ashok Raj
2018-02-22 11:44 ` Borislav Petkov
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