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 14:44:58 +0100 [thread overview]
Message-ID: <20180222134259.GD27489@pd.tnic> (raw)
In-Reply-To: <20180222131918.GB3797@araj-mobl1.jf.intel.com>
On Thu, Feb 22, 2018 at 05:19:18AM -0800, Raj, Ashok wrote:
> This isn't a simple WRMSR like others. Microcode engine needs to do
> a bunch of validation.
So this is slowly starting to resemble a real reason why not to. That
should be part of the code comment.
> We now have new guidance that the sibling must be spinning and not
> doing other things that can introduce instability around loading
> microcode.
Why isn't *this* in the code comment?
> I think its safer...
That's not good enough - it should be:
"It is not safe because... <insert reasons here>".
So that you can justify the overhead.
--
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 13:45 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
2018-02-22 13:19 ` Raj, Ashok
2018-02-22 13:44 ` Borislav Petkov [this message]
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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