linux-kernel - Re: [RESEND PATCH] Make Fujitsu Erratum 010001 patch can be applied on A64FX v1r0

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Date:   Mon, 18 Mar 2019 12:06:06 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     "Zhang, Lei" <zhang.lei@...fujitsu.com>,
        Catalin Marinas <catalin.marinas@....com>
Cc:     "Okamoto, Takayuki" <tokamoto@...fujitsu.com>,
        Will Deacon <will.deacon@....com>,
        James Morse <james.morse@....com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [RESEND PATCH] Make Fujitsu Erratum 010001 patch can be applied
 on A64FX v1r0

On Mon, Mar 18, 2019 at 03:05:09AM +0000, Zhang, Lei wrote:
> Thanks for your comments.
> I also have considered to use MIDR_CPU_VAR_REV macro,
> but the implication of (~MIDR_CPU_VAR_REV(1, 0)) is "NOT v1r0".
> I think it may cause confusion, so I choose the
> simple way (~(0x1 << MIDR_VARIANT_SHIFT)).

I think that either way is just as confusing, and the fact we're
assigning it to a mask (of bits to preserve) should make this clear. For
consistency, I'd prefer to use MIDR_CPU_VAR_REV().

Catalin, are you happy to take the below as a fix for v5.1?

Thanks,
Mark.

---->8----
>From 6439e9c0b1525e9d4c7be65552e6f2b1f9d1dbe0 Mon Sep 17 00:00:00 2001
From: "Okamoto, Takayuki" <tokamoto@...fujitsu.com>
Date: Fri, 15 Mar 2019 12:22:36 +0000
Subject: [PATCH] arm64: apply workaround on A64FX v1r0

Fujitsu erratum 010001 applies to A64FX v0r0 and v1r0, and we try to
handle either by masking MIDR with MIDR_FUJITSU_ERRATUM_010001_MASK
before comparing it to MIDR_FUJITSU_ERRATUM_010001.

Unfortunately, MIDR_FUJITSU_ERRATUM_010001 is constructed incorrectly
using MIDR_VARIANT(), which is intended to extract the variant field
from MIDR_EL1, rather than generate the field in-place. This results in
MIDR_FUJITSU_ERRATUM_010001 being all-ones, and we only match A64FX
v0r0.

This patch uses MIDR_CPU_VAR_REV() to generate an in-place mask for the
variant field, ensuring the we match both v0r0 and v1r0.

Fixes: 3e32131abc311a5c ("arm64: Add workaround for Fujitsu A64FX erratum 010001")
Signed-off-by: Zhang Lei <zhang.lei@...fujitsu.com>
[Mark: use MIDR_CPU_VAR_REV(), reword commit message]
Signed-off-by: Mark Rutland <mark.rutland@....com>
---
 arch/arm64/include/asm/cputype.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/cputype.h b/arch/arm64/include/asm/cputype.h
index 2afb1338b48a..f3b659587a36 100644
--- a/arch/arm64/include/asm/cputype.h
+++ b/arch/arm64/include/asm/cputype.h
@@ -129,7 +129,7 @@

 /* Fujitsu Erratum 010001 affects A64FX 1.0 and 1.1, (v0r0 and v1r0) */
 #define MIDR_FUJITSU_ERRATUM_010001		MIDR_FUJITSU_A64FX
-#define MIDR_FUJITSU_ERRATUM_010001_MASK	(~MIDR_VARIANT(1))
+#define MIDR_FUJITSU_ERRATUM_010001_MASK	(~MIDR_CPU_VAR_REV(1, 0))
 #define TCR_CLEAR_FUJITSU_ERRATUM_010001	(TCR_NFD1 | TCR_NFD0)

 #ifndef __ASSEMBLY__
-- 
2.11.0