linux-kernel - Re: [PATCH] arm64: apply ARM64_ERRATUM_845719 workaround for Brahma-B53 core

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Message-ID: <4c0bdd76-25c9-7171-4543-17a5fbdda31b@gmail.com>
Date:   Thu, 31 Oct 2019 10:18:42 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Will Deacon <will@...nel.org>,
        Florian Fainelli <f.fainelli@...il.com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        bcm-kernel-feedback-list@...adcom.com,
        Doug Berger <opendmb@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Vladimir Murzin <vladimir.murzin@....com>,
        John Garry <john.garry@...wei.com>,
        Zhang Lei <zhang.lei@...fujitsu.com>,
        Marc Zyngier <maz@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>, Qian Cai <cai@....pw>,
        Hanjun Guo <guohanjun@...wei.com>,
        Jeremy Linton <jeremy.linton@....com>,
        Andre Przywara <andre.przywara@....com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: apply ARM64_ERRATUM_845719 workaround for
 Brahma-B53 core

On 10/31/19 6:21 AM, Will Deacon wrote:
> On Tue, Oct 29, 2019 at 12:16:19PM -0700, Florian Fainelli wrote:
>> From: Doug Berger <opendmb@...il.com>
>>
>> The Broadcom Brahma-B53 core is susceptible to the issue described by
>> ARM64_ERRATUM_845719 so this commit enables the workaround to be applied
>> when executing on that core.
>>
>> Since there are now multiple entries to match, we must convert the
>> existing ARM64_ERRATUM_845719 into an erratum list.
> 
> Looks fine to me, but I have to ask: are you sure you don't want to select
> any of ARM64_ERRATUM_{826319, 827319, 824069, 819472, 843419} ?

Out of this list, we are only subject to 843419 (and 845719) since I am
told that only r0p4 (inclusive) and beyond are relevant.

Good thing that you mentioned 843419 because in our downstream kernel
(4.9) this is a "static" workaround in that once enabled, it just is
unconditionally active, whereas in later kernels there is some
additional run time determination of whether this is really needed, thanks!

> 
> Also, please can you update Documentation/arm64/silicon-errata.rst ?

Absolutely.
-- 
Florian