[PATCH] arm64: errata: Add Cortex-A55 to the repeat tlbi list

[James Morse]

Cortex-A55 is affected by an erratum where in rare circumstances the
CPUs may not handle a race between a break-before-make sequence on one
CPU, and another CPU accessing the same page. This could allow a store
to a page that has been unmapped.

Work around this by adding the affected CPUs to the list that needs
TLB sequences to be done twice.

Signed-off-by: James Morse <james.morse at arm.com>

---
This patch is based on arm64/for-next/core - I'll post it again come rc1
as this is probably too late for next.

SDEN: https://developer.arm.com/documentation/SDEN859338/1500/
---
 Documentation/arm64/silicon-errata.rst |  2 ++
 arch/arm64/Kconfig                     | 17 +++++++++++++++++
 arch/arm64/kernel/cpu_errata.c         |  5 +++++
 3 files changed, 24 insertions(+)

diff --git a/Documentation/arm64/silicon-errata.rst b/Documentation/arm64/silicon-errata.rst
index 17d9fc5d14fb..808ade4cc008 100644
--- a/Documentation/arm64/silicon-errata.rst
+++ b/Documentation/arm64/silicon-errata.rst
@@ -76,6 +76,8 @@ stable kernels.
 +----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Cortex-A55      | #1530923        | ARM64_ERRATUM_1530923       |
 +----------------+-----------------+-----------------+-----------------------------+
+| ARM            | Cortex-A55      | #2441007        | ARM64_ERRATUM_2441007       |
++----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Cortex-A57      | #832075         | ARM64_ERRATUM_832075        |
 +----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Cortex-A57      | #852523         | N/A                         |
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 1675310f1791..20d082d54bd8 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -634,6 +634,23 @@ config ARM64_ERRATUM_1530923
 config ARM64_WORKAROUND_REPEAT_TLBI
 	bool
 
+config ARM64_ERRATUM_2441007
+	bool "Cortex-A55: Completion of affected memory accesses might not be guaranteed by completion of a TLBI"
+	default y
+	select ARM64_WORKAROUND_REPEAT_TLBI
+	help
+	  This option adds a workaround for ARM Cortex-A55 erratum #2441007.
+
+	  Under very rare circumstances, affected Cortex-A55 CPUs
+	  may not handle a race between a break-before-make sequence on one
+	  CPU, and another CPU accessing the same page. This could allow a
+	  store to a page that has been unmapped.
+
+	  Work around this by adding the affected CPUs to the list that needs
+	  TLB sequences to be done twice.
+
+	  If unsure, say Y.
+
 config ARM64_ERRATUM_1286807
 	bool "Cortex-A76: Modification of the translation table for a virtual address might lead to read-after-read ordering violation"
 	default y
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 58ca4f6b25d6..89ac00084f38 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -230,6 +230,11 @@ static const struct arm64_cpu_capabilities arm64_repeat_tlbi_list[] = {
 		ERRATA_MIDR_RANGE(MIDR_QCOM_KRYO_4XX_GOLD, 0xc, 0xe, 0xf, 0xe),
 	},
 #endif
+#ifdef CONFIG_ARM64_ERRATUM_2441007
+	{
+		ERRATA_MIDR_ALL_VERSIONS(MIDR_CORTEX_A55),
+	},
+#endif
 #ifdef CONFIG_ARM64_ERRATUM_2441009
 	{
 		/* Cortex-A510 r0p0 -> r1p1. Fixed in r1p2 */
-- 
2.30.2