linux-kernel - Re: [PATCH v4] arm64: errata: Work around AmpereOne's erratum AC04_CPU

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Message-ID: <aDCDGZ-G-nCP3hJI@finisterre.sirena.org.uk>
Date: Fri, 23 May 2025 15:15:53 +0100
From: Mark Brown <broonie@...nel.org>
To: D Scott Phillips <scott@...amperecomputing.com>
Cc: Catalin Marinas <catalin.marinas@....com>,
	James Clark <james.clark@...aro.org>,
	James Morse <james.morse@....com>, Joey Gouly <joey.gouly@....com>,
	Kevin Brodsky <kevin.brodsky@....com>,
	Marc Zyngier <maz@...nel.org>, Mark Rutland <mark.rutland@....com>,
	Oliver Upton <oliver.upton@...ux.dev>,
	"Rob Herring  (Arm)" <robh@...nel.org>,
	Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>,
	Shiqi Liu <shiqiliu@...t.edu.cn>, Will Deacon <will@...nel.org>,
	Yicong Yang <yangyicong@...ilicon.com>, kvmarm@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] arm64: errata: Work around AmpereOne's erratum
 AC04_CPU_23

On Tue, May 13, 2025 at 11:45:14AM -0700, D Scott Phillips wrote:
> On AmpereOne AC04, updates to HCR_EL2 can rarely corrupt simultaneous
> translations for data addresses initiated by load/store instructions.
> Only instruction initiated translations are vulnerable, not translations
> from prefetches for example. A DSB before the store to HCR_EL2 is
> sufficient to prevent older instructions from hitting the window for
> corruption, and an ISB after is sufficient to prevent younger
> instructions from hitting the window for corruption.

This patch, which is in -next as fed55f49fad181be9dfb93c0, breaks the
build of at least the vDSO selftests:

$ make -C tools/testing/selftests ARCH=arm64 LLVM=1 TARGETS=vDSO

  CC       vdso_test_chacha
In file included from vgetrandom-chacha.S:9:
In file included from ./../../../../arch/arm64/kernel/vdso/vgetrandom-chacha.S:5:
In file included from /home/broonie/git/bisect/tools/testing/selftests/../../../arch/arm64/include/asm/assembler.h:21:
In file included from /home/broonie/git/bisect/tools/testing/selftests/../../../arch/arm64/include/asm/cpufeature.h:13:
/home/broonie/git/bisect/tools/testing/selftests/../../../arch/arm64/include/asm/sysreg.h:1097:5: error: function-like macro 'IS_ENABLED' is not defined
 1097 | #if IS_ENABLED(CONFIG_AMPERE_ERRATUM_AC04_CPU_23)
      |     ^
1 error generated.

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