When software issues a Cache Maintenance Operation (CMO) targeting a dirty cache line, the CPU and DSU cluster may optimize the operation by combining the CopyBack Write and CMO into a single combined CopyBack Write plus CMO transaction presented to the interconnect (MCN). For these combined transactions, the MCN splits the operation into two separate transactions, one Write and one CMO, and then propagates the write and optionally the CMO to the downstream memory system or external Point of Serialization (PoS). However, the MCN may return an early CompCMO response to the DSU cluster before the corresponding Write and CMO transactions have completed at the external PoS or downstream memory. As a result, stale data may be observed by external observers that are directly connected to the external PoS or downstream memory.
This erratum affects any system topology in which the following conditions apply: - The Point of Serialization (PoS) is located downstream of the interconnect. - A downstream observer accesses memory directly, bypassing the interconnect.
Conditions: This erratum occurs only when all of the following conditions are met: 1. Software executes a data cache maintenance operation, specifically, a clean or invalidate by virtual address (DC CVAC, DC CIVAC, or DC IVAC), that hits on unique dirty data in the CPU or DSU cache. This results in a combined CopyBack and CMO being issued to the interconnect. 2. The interconnect splits the combined transaction into separate Write and CMO transactions and returns an early completion response to the CPU or DSU before the write has completed at the downstream memory or PoS. 3. A downstream observer accesses the affected memory address after the early completion response is issued but before the actual memory write has completed. This allows the observer to read stale data that has not yet been updated at the PoS or downstream memory.
The implementation of workaround put a second loop of CMOs at the same virtual address whose operation meet erratum conditions to wait until cache data be cleaned to PoC.. This way of implementation mitigates performance panalty compared to purly duplicate orignial CMO.
Cc: stable@vger.kernel.org # 6.12.x Signed-off-by: Lucas Wei lucaswei@google.com --- Documentation/arch/arm64/silicon-errata.rst | 3 ++ arch/arm64/Kconfig | 19 +++++++++++++ arch/arm64/include/asm/assembler.h | 10 +++++++ arch/arm64/kernel/cpu_errata.c | 31 +++++++++++++++++++++ arch/arm64/mm/cache.S | 13 ++++++++- arch/arm64/tools/cpucaps | 1 + 6 files changed, 76 insertions(+), 1 deletion(-)
diff --git a/Documentation/arch/arm64/silicon-errata.rst b/Documentation/arch/arm64/silicon-errata.rst index a7ec57060f64..98efdf528719 100644 --- a/Documentation/arch/arm64/silicon-errata.rst +++ b/Documentation/arch/arm64/silicon-errata.rst @@ -213,6 +213,9 @@ stable kernels. | ARM | GIC-700 | #2941627 | ARM64_ERRATUM_2941627 | +----------------+-----------------+-----------------+-----------------------------+ +----------------+-----------------+-----------------+-----------------------------+ +| ARM | SI L1 | #4311569 | ARM64_ERRATUM_4311569 | ++----------------+-----------------+-----------------+-----------------------------+ ++----------------+-----------------+-----------------+-----------------------------+ | Broadcom | Brahma-B53 | N/A | ARM64_ERRATUM_845719 | +----------------+-----------------+-----------------+-----------------------------+ | Broadcom | Brahma-B53 | N/A | ARM64_ERRATUM_843419 | diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 93173f0a09c7..89326bb26f48 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -1155,6 +1155,25 @@ config ARM64_ERRATUM_3194386
If unsure, say Y.
+config ARM64_ERRATUM_4311569 + bool "SI L1: 4311569: workaround for premature CMO completion erratum" + default y + help + This option adds the workaround for ARM SI L1 erratum 4311569. + + The erratum of SI L1 can cause an early response to a combined write + and cache maintenance operation (WR+CMO) before the operation is fully + completed to the Point of Serialization (POS). + This can result in a non-I/O coherent agent observing stale data, + potentially leading to system instability or incorrect behavior. + + Enabling this option implements a software workaround by inserting a + second loop of Cache Maintenance Operation (CMO) immediately following the + end of function to do CMOs. This ensures that the data is correctly serialized + before the buffer is handed off to a non-coherent agent. + + 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 f0ca7196f6fa..d3d46e5f7188 100644 --- a/arch/arm64/include/asm/assembler.h +++ b/arch/arm64/include/asm/assembler.h @@ -381,6 +381,9 @@ alternative_endif .macro dcache_by_myline_op op, domain, start, end, linesz, tmp, fixup sub \tmp, \linesz, #1 bic \start, \start, \tmp +alternative_if ARM64_WORKAROUND_4311569 + mov \tmp, \start +alternative_else_nop_endif .Ldcache_op@: .ifc \op, cvau __dcache_op_workaround_clean_cache \op, \start @@ -402,6 +405,13 @@ alternative_endif add \start, \start, \linesz cmp \start, \end b.lo .Ldcache_op@ +alternative_if ARM64_WORKAROUND_4311569 + .ifnc \op, cvau + mov \start, \tmp + mov \tmp, xzr + cbnz \start, .Ldcache_op@ + .endif +alternative_else_nop_endif dsb \domain
_cond_uaccess_extable .Ldcache_op@, \fixup diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c index 8cb3b575a031..c69678c512f1 100644 --- a/arch/arm64/kernel/cpu_errata.c +++ b/arch/arm64/kernel/cpu_errata.c @@ -141,6 +141,30 @@ has_mismatched_cache_type(const struct arm64_cpu_capabilities *entry, return (ctr_real != sys) && (ctr_raw != sys); }
+#ifdef CONFIG_ARM64_ERRATUM_4311569 +DEFINE_STATIC_KEY_FALSE(arm_si_l1_workaround_4311569); +static int __init early_arm_si_l1_workaround_4311569_cfg(char *arg) +{ + static_branch_enable(&arm_si_l1_workaround_4311569); + pr_info("Enabling cache maintenance workaround for ARM SI-L1 erratum 4311569\n"); + + return 0; +} +early_param("arm_si_l1_workaround_4311569", early_arm_si_l1_workaround_4311569_cfg); + +/* + * We have some earlier use cases to call cache maintenance operation functions, for example, + * dcache_inval_poc() and dcache_clean_poc() in head.S, before making decision to turn on this + * workaround. Since the scope of this workaround is limited to non-coherent DMA agents, its + * safe to have the workaround off by default. + */ +static bool +need_arm_si_l1_workaround_4311569(const struct arm64_cpu_capabilities *entry, int scope) +{ + return static_branch_unlikely(&arm_si_l1_workaround_4311569); +} +#endif + static void cpu_enable_trap_ctr_access(const struct arm64_cpu_capabilities *cap) { @@ -870,6 +894,13 @@ const struct arm64_cpu_capabilities arm64_errata[] = { ERRATA_MIDR_RANGE_LIST(erratum_spec_ssbs_list), }, #endif +#ifdef CONFIG_ARM64_ERRATUM_4311569 + { + .capability = ARM64_WORKAROUND_4311569, + .type = ARM64_CPUCAP_SYSTEM_FEATURE, + .matches = need_arm_si_l1_workaround_4311569, + }, +#endif #ifdef CONFIG_ARM64_WORKAROUND_SPECULATIVE_UNPRIV_LOAD { .desc = "ARM errata 2966298, 3117295", diff --git a/arch/arm64/mm/cache.S b/arch/arm64/mm/cache.S index 503567c864fd..ddf0097624ed 100644 --- a/arch/arm64/mm/cache.S +++ b/arch/arm64/mm/cache.S @@ -143,9 +143,14 @@ SYM_FUNC_END(dcache_clean_pou) * - end - kernel end address of region */ SYM_FUNC_START(__pi_dcache_inval_poc) +alternative_if ARM64_WORKAROUND_4311569 + mov x4, x0 + mov x5, x1 + mov x6, #1 +alternative_else_nop_endif dcache_line_size x2, x3 sub x3, x2, #1 - tst x1, x3 // end cache line aligned? +again: tst x1, x3 // end cache line aligned? bic x1, x1, x3 b.eq 1f dc civac, x1 // clean & invalidate D / U line @@ -158,6 +163,12 @@ SYM_FUNC_START(__pi_dcache_inval_poc) 3: add x0, x0, x2 cmp x0, x1 b.lo 2b +alternative_if ARM64_WORKAROUND_4311569 + mov x0, x4 + mov x1, x5 + sub x6, x6, #1 + cbz x6, again +alternative_else_nop_endif dsb sy ret SYM_FUNC_END(__pi_dcache_inval_poc) diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps index 0fac75f01534..856b6cf6e71e 100644 --- a/arch/arm64/tools/cpucaps +++ b/arch/arm64/tools/cpucaps @@ -103,6 +103,7 @@ WORKAROUND_2077057 WORKAROUND_2457168 WORKAROUND_2645198 WORKAROUND_2658417 +WORKAROUND_4311569 WORKAROUND_AMPERE_AC03_CPU_38 WORKAROUND_AMPERE_AC04_CPU_23 WORKAROUND_TRBE_OVERWRITE_FILL_MODE