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Subject[PATCH] [stable 4.14] arm64: Add work around for Arm Cortex-A55 Erratum 1024718
Date
commit ece1397cbc89c51914fae1aec729539cfd8bd62b upstream

Some variants of the Arm Cortex-55 cores (r0p0, r0p1, r1p0) suffer
from an erratum 1024718, which causes incorrect updates when DBM/AP
bits in a page table entry is modified without a break-before-make
sequence. The work around is to disable the hardware DBM feature
on the affected cores. The hardware Access Flag management features
is not affected.

The hardware DBM feature is a non-conflicting capability, i.e, the
kernel could handle cores using the feature and those without having
the features running at the same time. So this work around is detected
at early boot time, rather than delaying it until the CPUs are brought
up into the kernel with MMU turned on. This also avoids other complexities
with late CPUs turning online, with or without the hardware DBM features.

Cc: stable@vger.kernel.org # v4.14
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
Note: The upstream commit is on top of a reworked capability
infrastructure for arm64 heterogeneous systems, which allows
delaying the CPU model checks. This backport is based on the
original version of the patch [0], which checks the affected
CPU models during the early boot.

[0] https://lkml.kernel.org/r/20180116102323.3470-1-suzuki.poulose@arm.com
---

Documentation/arm64/silicon-errata.txt | 1 +
arch/arm64/Kconfig | 14 ++++++++++++
arch/arm64/include/asm/assembler.h | 40 ++++++++++++++++++++++++++++++++++
arch/arm64/include/asm/cputype.h | 2 ++
arch/arm64/mm/proc.S | 5 +++++
5 files changed, 62 insertions(+)

diff --git a/Documentation/arm64/silicon-errata.txt b/Documentation/arm64/silicon-errata.txt
index f3d0d31..e4fe6ad 100644
--- a/Documentation/arm64/silicon-errata.txt
+++ b/Documentation/arm64/silicon-errata.txt
@@ -55,6 +55,7 @@ stable kernels.
| ARM | Cortex-A57 | #834220 | ARM64_ERRATUM_834220 |
| ARM | Cortex-A72 | #853709 | N/A |
| ARM | Cortex-A73 | #858921 | ARM64_ERRATUM_858921 |
+| ARM | Cortex-A55 | #1024718 | ARM64_ERRATUM_1024718 |
| ARM | MMU-500 | #841119,#826419 | N/A |
| | | | |
| Cavium | ThunderX ITS | #22375, #24313 | CAVIUM_ERRATUM_22375 |
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index c2abb4e..2d5f7ac 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -443,6 +443,20 @@ config ARM64_ERRATUM_843419

If unsure, say Y.

+config ARM64_ERRATUM_1024718
+ bool "Cortex-A55: 1024718: Update of DBM/AP bits without break before make might result in incorrect update"
+ default y
+ help
+ This option adds work around for Arm Cortex-A55 Erratum 1024718.
+
+ Affected Cortex-A55 cores (r0p0, r0p1, r1p0) could cause incorrect
+ update of the hardware dirty bit when the DBM/AP bits are updated
+ without a break-before-make. The work around is to disable the usage
+ of hardware DBM locally on the affected cores. CPUs not affected by
+ erratum will continue to use the feature.
+
+ If unsure, say Y.
+
config CAVIUM_ERRATUM_22375
bool "Cavium erratum 22375, 24313"
default y
diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index 463619d..25b2a41 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -25,6 +25,7 @@

#include <asm/asm-offsets.h>
#include <asm/cpufeature.h>
+#include <asm/cputype.h>
#include <asm/page.h>
#include <asm/pgtable-hwdef.h>
#include <asm/ptrace.h>
@@ -495,4 +496,43 @@ alternative_endif
and \phys, \pte, #(((1 << (48 - PAGE_SHIFT)) - 1) << PAGE_SHIFT)
.endm

+/*
+ * Check the MIDR_EL1 of the current CPU for a given model and a range of
+ * variant/revision. See asm/cputype.h for the macros used below.
+ *
+ * model: MIDR_CPU_MODEL of CPU
+ * rv_min: Minimum of MIDR_CPU_VAR_REV()
+ * rv_max: Maximum of MIDR_CPU_VAR_REV()
+ * res: Result register.
+ * tmp1, tmp2, tmp3: Temporary registers
+ *
+ * Corrupts: res, tmp1, tmp2, tmp3
+ * Returns: 0, if the CPU id doesn't match. Non-zero otherwise
+ */
+ .macro cpu_midr_match model, rv_min, rv_max, res, tmp1, tmp2, tmp3
+ mrs \res, midr_el1
+ mov_q \tmp1, (MIDR_REVISION_MASK | MIDR_VARIANT_MASK)
+ mov_q \tmp2, MIDR_CPU_MODEL_MASK
+ and \tmp3, \res, \tmp2 // Extract model
+ and \tmp1, \res, \tmp1 // rev & variant
+ mov_q \tmp2, \model
+ cmp \tmp3, \tmp2
+ cset \res, eq
+ cbz \res, .Ldone\@ // Model matches ?
+
+ .if (\rv_min != 0) // Skip min check if rv_min == 0
+ mov_q \tmp3, \rv_min
+ cmp \tmp1, \tmp3
+ cset \res, ge
+ .endif // \rv_min != 0
+ /* Skip rv_max check if rv_min == rv_max && rv_min != 0 */
+ .if ((\rv_min != \rv_max) || \rv_min == 0)
+ mov_q \tmp2, \rv_max
+ cmp \tmp1, \tmp2
+ cset \tmp2, le
+ and \res, \res, \tmp2
+ .endif
+.Ldone\@:
+ .endm
+
#endif /* __ASM_ASSEMBLER_H */
diff --git a/arch/arm64/include/asm/cputype.h b/arch/arm64/include/asm/cputype.h
index be7bd19..30da091 100644
--- a/arch/arm64/include/asm/cputype.h
+++ b/arch/arm64/include/asm/cputype.h
@@ -78,6 +78,7 @@

#define ARM_CPU_PART_AEM_V8 0xD0F
#define ARM_CPU_PART_FOUNDATION 0xD00
+#define ARM_CPU_PART_CORTEX_A55 0xD05
#define ARM_CPU_PART_CORTEX_A57 0xD07
#define ARM_CPU_PART_CORTEX_A72 0xD08
#define ARM_CPU_PART_CORTEX_A53 0xD03
@@ -98,6 +99,7 @@
#define QCOM_CPU_PART_KRYO 0x200

#define MIDR_CORTEX_A53 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_CORTEX_A53)
+#define MIDR_CORTEX_A55 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_CORTEX_A55)
#define MIDR_CORTEX_A57 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_CORTEX_A57)
#define MIDR_CORTEX_A72 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_CORTEX_A72)
#define MIDR_CORTEX_A73 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_CORTEX_A73)
diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index 139320a..e338165 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -438,6 +438,11 @@ ENTRY(__cpu_setup)
cbz x9, 2f
cmp x9, #2
b.lt 1f
+#ifdef CONFIG_ARM64_ERRATUM_1024718
+ /* Disable hardware DBM on Cortex-A55 r0p0, r0p1 & r1p0 */
+ cpu_midr_match MIDR_CORTEX_A55, MIDR_CPU_VAR_REV(0, 0), MIDR_CPU_VAR_REV(1, 0), x1, x2, x3, x4
+ cbnz x1, 1f
+#endif
orr x10, x10, #TCR_HD // hardware Dirty flag update
1: orr x10, x10, #TCR_HA // hardware Access flag update
2:
--
2.7.4
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