linux-kernel - Re: [PATCH AUTOSEL 5.15 11/12] x86/barrier: Do not serialize MSR accesses on AMD

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Message-ID: <Z0iRzPpGvpeYzA4H@sashalap>
Date: Thu, 28 Nov 2024 10:52:44 -0500
From: Sasha Levin <sashal@...nel.org>
To: Borislav Petkov <bp@...en8.de>
Cc: linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	tglx@...utronix.de, mingo@...hat.com, dave.hansen@...ux.intel.com,
	x86@...nel.org, puwen@...on.cn, seanjc@...gle.com,
	kim.phillips@....com, jmattson@...gle.com, babu.moger@....com,
	peterz@...radead.org, rick.p.edgecombe@...el.com, brgerst@...il.com,
	ashok.raj@...el.com, mjguzik@...il.com, jpoimboe@...nel.org,
	nik.borisov@...e.com, aik@....com, vegard.nossum@...cle.com,
	daniel.sneddon@...ux.intel.com, acdunlap@...gle.com,
	Erwan Velu <erwanaliasr1@...il.com>, pavel@...x.de
Subject: Re: [PATCH AUTOSEL 5.15 11/12] x86/barrier: Do not serialize MSR
 accesses on AMD

On Thu, Nov 28, 2024 at 12:59:24PM +0100, Borislav Petkov wrote:
>Hey folks,
>
>On Mon, Jan 15, 2024 at 06:26:56PM -0500, Sasha Levin wrote:
>> From: "Borislav Petkov (AMD)" <bp@...en8.de>
>>
>> [ Upstream commit 04c3024560d3a14acd18d0a51a1d0a89d29b7eb5 ]
>>
>> AMD does not have the requirement for a synchronization barrier when
>> acccessing a certain group of MSRs. Do not incur that unnecessary
>> penalty there.
>
>Erwan just mentioned that this one is not in 6.1 and in 5.15. And I have mails
>about it getting picked up by AUTOSEL.
>
>Did the AI reconsider in the meantime?

You've missed the 5.10 mail :)

Pavel objected to it so I've dropped it: https://lore.kernel.org/all/Zbli7QIGVFT8EtO4@sashalap/

-- 
Thanks,
Sasha