linux-kernel - [PATCH 2/2] arm64: errata: Work around AmpereOne's erratum AC04_CPU

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Message-ID: <20250415154711.1698544-2-scott@os.amperecomputing.com>
Date: Tue, 15 Apr 2025 08:47:11 -0700
From: D Scott Phillips <scott@...amperecomputing.com>
To: 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 Brown <broonie@...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 (open list)
Subject: [PATCH 2/2] arm64: errata: Work around AmpereOne's erratum AC04_CPU_23

Updates to HCR_EL2 can rarely corrupt simultaneous translations from
either earlier translations (back to the previous dsb) or later
translations (up to the next isb). Put a dsb before and isb after writes
to HCR_EL2.

Signed-off-by: D Scott Phillips <scott@...amperecomputing.com>
---
 arch/arm64/Kconfig              | 13 +++++++++++++
 arch/arm64/include/asm/sysreg.h |  7 +++++++
 arch/arm64/kernel/cpu_errata.c  | 14 ++++++++++++++
 arch/arm64/tools/cpucaps        |  1 +
 4 files changed, 35 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index e5fd87446a3b8..2a2e1c8de6a16 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -481,6 +481,19 @@ config AMPERE_ERRATUM_AC03_CPU_38
 
 	  If unsure, say Y.
 
+config AMPERE_ERRATUM_AC04_CPU_23
+        bool "AmpereOne: AC04_CPU_23:  Failure to synchronize writes to HCR_EL2 may corrupt address translations."
+	default y
+	help
+	  This option adds an alternative code sequence to work around Ampere
+	  errata AC04_CPU_23 on AmpereOne.
+
+	  Updates to HCR_EL2 can rarely corrupt simultaneous translations from
+	  either earlier translations (back to the previous dsb) or later
+	  translations (up to the next isb).
+
+	  If unsure, say Y.
+
 config ARM64_WORKAROUND_CLEAN_CACHE
 	bool
 
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index e7781f7e7f7a7..253de5bc68834 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -1142,6 +1142,10 @@
 	(IS_ENABLED(CONFIG_AMPERE_ERRATUM_AC03_CPU_36) &&	\
 	 __sysreg_is_hcr_el2(r) &&				\
 	 alternative_has_cap_unlikely(ARM64_WORKAROUND_AMPERE_AC03_CPU_36))
+#define __hcr_el2_ac04_cpu_23(r)				\
+	(IS_ENABLED(CONFIG_AMPERE_ERRATUM_AC04_CPU_23) &&	\
+	 __sysreg_is_hcr_el2(r) &&				\
+	 alternative_has_cap_unlikely(ARM64_WORKAROUND_AMPERE_AC04_CPU_23))
 
 /*
  * The "Z" constraint normally means a zero immediate, but when combined with
@@ -1154,6 +1158,9 @@
 		asm volatile("mrs %0, daif; msr daifset, #0xf;"	\
 			     "msr hcr_el2, %x1; msr daif, %0"	\
 		: "=&r"(__daif) : "rZ" (__val));		\
+	} else if (__hcr_el2_ac04_cpu_23(r)) {			\
+		asm volatile("dsb nsh; msr hcr_el2, %x0; isb"	\
+			     : : "rZ" (__val));			\
 	} else {						\
 		asm volatile("msr " __stringify(r) ", %x0"	\
 			     : : "rZ" (__val));			\
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 89be85bf631fd..bdb92872791f3 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -564,6 +564,13 @@ static const struct midr_range erratum_ac03_cpu_38_list[] = {
 };
 #endif
 
+#ifdef CONFIG_AMPERE_ERRATUM_AC04_CPU_23
+static const struct midr_range erratum_ac04_cpu_23_list[] = {
+	MIDR_ALL_VERSIONS(MIDR_AMPERE1A),
+	{},
+};
+#endif
+
 const struct arm64_cpu_capabilities arm64_errata[] = {
 #ifdef CONFIG_ARM64_WORKAROUND_CLEAN_CACHE
 	{
@@ -889,6 +896,13 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
 		.capability = ARM64_WORKAROUND_AMPERE_AC03_CPU_38,
 		ERRATA_MIDR_RANGE_LIST(erratum_ac03_cpu_38_list),
 	},
+#endif
+#ifdef CONFIG_AMPERE_ERRATUM_AC04_CPU_23
+	{
+		.desc = "AmpereOne erratum AC04_CPU_23",
+		.capability = ARM64_WORKAROUND_AMPERE_AC04_CPU_23,
+		ERRATA_MIDR_RANGE_LIST(erratum_ac04_cpu_23_list),
+	},
 #endif
 	{
 		.desc = "Broken CNTVOFF_EL2",
diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
index f430fd5900d15..2b3afe4421af9 100644
--- a/arch/arm64/tools/cpucaps
+++ b/arch/arm64/tools/cpucaps
@@ -95,6 +95,7 @@ WORKAROUND_2645198
 WORKAROUND_2658417
 WORKAROUND_AMPERE_AC03_CPU_36
 WORKAROUND_AMPERE_AC03_CPU_38
+WORKAROUND_AMPERE_AC04_CPU_23
 WORKAROUND_TRBE_OVERWRITE_FILL_MODE
 WORKAROUND_TSB_FLUSH_FAILURE
 WORKAROUND_TRBE_WRITE_OUT_OF_RANGE
-- 
2.48.1