[1/2] arm64: Workaround for Cavium ThunderX2 erratum 219

Commit Message

Jayachandran Chandrasekharan Nair Oct. 11, 2019, 10:35 a.m. UTC

From: Marc Zyngier <[e-mail]>

A prefetch, load or store instruction after a TTBR change but before the
corresponding context synchronization barrier can cause a spurious Data
Abort on Cavium ThunderX2.

An optimization introduced in commit c7b9adaf85f818 ("arm64: entry: Add
exception trampoline page for exceptions from EL0") for prefetching
trampoline vectors ends up triggering this issue when KPTI is enabled.

Workaround is to turn off the prefetch for ThunderX2 where it does not
have an advantage.

Signed-off-by: Marc Zyngier <[e-mail]>
[Updated commit message and erratum information - jnair]
Signed-off-by: Jayachandran Chandrasekharan Nair <[e-mail]>
Cc: [e-mail]
---
 Documentation/arm64/silicon-errata.rst |  2 ++
 arch/arm64/Kconfig                     | 12 ++++++++++++
 arch/arm64/include/asm/cpucaps.h       |  3 ++-
 arch/arm64/kernel/cpu_errata.c         | 15 +++++++++++++++
 arch/arm64/kernel/entry.S              |  2 ++
 5 files changed, 33 insertions(+), 1 deletion(-)

Patch

diff --git a/Documentation/arm64/silicon-errata.rst b/Documentation/arm64/silicon-errata.rst
index 17ea3fecddaa..ab7ed2fd072f 100644
--- a/Documentation/arm64/silicon-errata.rst
+++ b/Documentation/arm64/silicon-errata.rst
@@ -107,6 +107,8 @@  stable kernels.
 +----------------+-----------------+-----------------+-----------------------------+
 | Cavium         | ThunderX2 SMMUv3| #126            | N/A                         |
 +----------------+-----------------+-----------------+-----------------------------+
+| Cavium         | ThunderX2 Core  | #219            | CAVIUM_TX2_ERRATUM_219      |
++----------------+-----------------+-----------------+-----------------------------+
 +----------------+-----------------+-----------------+-----------------------------+
 | Freescale/NXP  | LS2080A/LS1043A | A-008585        | FSL_ERRATUM_A008585         |
 +----------------+-----------------+-----------------+-----------------------------+
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 41a9b4257b72..d2c7c9b22dae 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -617,6 +617,18 @@  config CAVIUM_ERRATUM_30115
 
 	  If unsure, say Y.
 
+config CAVIUM_TX2_ERRATUM_219
+	bool "Cavium ThunderX2 erratum 219: PRFM between TTBR change and ISB fails"
+	default y
+	help
+	  On Cavium ThunderX2, a load/store/prefetch instruction after a
+	  change to TTBR and before the corresponding context synchronization
+	  operation can cause a spurious Data Abort to be delivered to any
+	  hardware thread in the CPU core.
+
+	  Workaround is to drop the optimization which does this. If unsure
+	  say Y
+
 config QCOM_FALKOR_ERRATUM_1003
 	bool "Falkor E1003: Incorrect translation due to ASID change"
 	default y
diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index f19fe4b9acc4..a0666dcff72a 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -52,7 +52,8 @@ 
 #define ARM64_HAS_IRQ_PRIO_MASKING		42
 #define ARM64_HAS_DCPODP			43
 #define ARM64_WORKAROUND_1463225		44
+#define ARM64_WORKAROUND_CAVIUM_TX2_219		45
 
-#define ARM64_NCAPS				45
+#define ARM64_NCAPS				46
 
 #endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 1e43ba5c79b7..1bbb89d0379a 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -712,6 +712,14 @@  static const struct midr_range erratum_1418040_list[] = {
 };
 #endif
 
+#ifdef CONFIG_CAVIUM_TX2_ERRATUM_219
+static const struct midr_range tx2_family_cpus[] = {
+	MIDR_ALL_VERSIONS(MIDR_BRCM_VULCAN),
+	MIDR_ALL_VERSIONS(MIDR_CAVIUM_THUNDERX2),
+	{},
+};
+#endif
+
 const struct arm64_cpu_capabilities arm64_errata[] = {
 #ifdef CONFIG_ARM64_WORKAROUND_CLEAN_CACHE
 	{
@@ -851,6 +859,13 @@  const struct arm64_cpu_capabilities arm64_errata[] = {
 		.type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM,
 		.matches = has_cortex_a76_erratum_1463225,
 	},
+#endif
+#ifdef CONFIG_CAVIUM_TX2_ERRATUM_219
+	{
+		.desc = "ThunderX2 erratum 219",
+		.capability = ARM64_WORKAROUND_CAVIUM_TX2_219,
+		ERRATA_MIDR_RANGE_LIST(tx2_family_cpus),
+	},
 #endif
 	{
 	}
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 84a822748c84..c282e6570a5b 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -1070,7 +1070,9 @@  alternative_insn isb, nop, ARM64_WORKAROUND_QCOM_FALKOR_E1003
 #else
 	ldr	x30, =vectors
 #endif
+alternative_if_not ARM64_WORKAROUND_CAVIUM_TX2_219
 	prfm	plil1strm, [x30, #(1b - tramp_vectors)]
+alternative_else_nop_endif
 	msr	vbar_el1, x30
 	add	x30, x30, #(1b - tramp_vectors)
 	isb