From 116c81f427ff6c5380850963e3fb8798cc821d2b Mon Sep 17 00:00:00 2001 From: Suzuki K Poulose Date: Fri, 9 Sep 2016 14:07:16 +0100 Subject: [PATCH] arm64: Work around systems with mismatched cache line sizes Systems with differing CPU i-cache/d-cache line sizes can cause problems with the cache management by software when the execution is migrated from one to another. Usually, the application reads the cache size on a CPU and then uses that length to perform cache operations. However, if it gets migrated to another CPU with a smaller cache line size, things could go completely wrong. To prevent such cases, always use the smallest cache line size among the CPUs. The kernel CPU feature infrastructure already keeps track of the safe value for all CPUID registers including CTR. This patch works around the problem by : For kernel, dynamically patch the kernel to read the cache size from the system wide copy of CTR_EL0. For applications, trap read accesses to CTR_EL0 (by clearing the SCTLR.UCT) and emulate the mrs instruction to return the system wide safe value of CTR_EL0. For faster access (i.e, avoiding to lookup the system wide value of CTR_EL0 via read_system_reg), we keep track of the pointer to table entry for CTR_EL0 in the CPU feature infrastructure. Cc: Mark Rutland Cc: Andre Przywara Cc: Will Deacon Cc: Catalin Marinas Signed-off-by: Suzuki K Poulose Signed-off-by: Will Deacon --- arch/arm64/include/asm/assembler.h | 24 ++++++++++++++++++++++-- arch/arm64/include/asm/cpufeature.h | 3 ++- arch/arm64/include/asm/esr.h | 8 ++++++++ arch/arm64/include/asm/sysreg.h | 1 + arch/arm64/kernel/asm-offsets.c | 2 ++ arch/arm64/kernel/cpu_errata.c | 22 ++++++++++++++++++++++ arch/arm64/kernel/traps.c | 14 ++++++++++++++ 7 files changed, 71 insertions(+), 3 deletions(-) diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h index a4bb3f52d9ef..f09a5ae48a44 100644 --- a/arch/arm64/include/asm/assembler.h +++ b/arch/arm64/include/asm/assembler.h @@ -216,6 +216,20 @@ lr .req x30 // link register .macro mmid, rd, rn ldr \rd, [\rn, #MM_CONTEXT_ID] .endm +/* + * read_ctr - read CTR_EL0. If the system has mismatched + * cache line sizes, provide the system wide safe value + * from arm64_ftr_reg_ctrel0.sys_val + */ + .macro read_ctr, reg +alternative_if_not ARM64_MISMATCHED_CACHE_LINE_SIZE + mrs \reg, ctr_el0 // read CTR + nop +alternative_else + ldr_l \reg, arm64_ftr_reg_ctrel0 + ARM64_FTR_SYSVAL +alternative_endif + .endm + /* * raw_dcache_line_size - get the minimum D-cache line size on this CPU @@ -232,7 +246,10 @@ lr .req x30 // link register * dcache_line_size - get the safe D-cache line size across all CPUs */ .macro dcache_line_size, reg, tmp - raw_dcache_line_size \reg, \tmp + read_ctr \tmp + ubfm \tmp, \tmp, #16, #19 // cache line size encoding + mov \reg, #4 // bytes per word + lsl \reg, \reg, \tmp // actual cache line size .endm /* @@ -250,7 +267,10 @@ lr .req x30 // link register * icache_line_size - get the safe I-cache line size across all CPUs */ .macro icache_line_size, reg, tmp - raw_icache_line_size \reg, \tmp + read_ctr \tmp + and \tmp, \tmp, #0xf // cache line size encoding + mov \reg, #4 // bytes per word + lsl \reg, \reg, \tmp // actual cache line size .endm /* diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index 6806b86ab791..758d74fedfad 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -39,8 +39,9 @@ #define ARM64_WORKAROUND_CAVIUM_27456 12 #define ARM64_HAS_32BIT_EL0 13 #define ARM64_HYP_OFFSET_LOW 14 +#define ARM64_MISMATCHED_CACHE_LINE_SIZE 15 -#define ARM64_NCAPS 15 +#define ARM64_NCAPS 16 #ifndef __ASSEMBLY__ diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h index 9875b326a73e..d14c478976d0 100644 --- a/arch/arm64/include/asm/esr.h +++ b/arch/arm64/include/asm/esr.h @@ -149,6 +149,9 @@ ((op2) << ESR_ELx_SYS64_ISS_OP2_SHIFT) | \ ((crn) << ESR_ELx_SYS64_ISS_CRN_SHIFT) | \ ((crm) << ESR_ELx_SYS64_ISS_CRM_SHIFT)) + +#define ESR_ELx_SYS64_ISS_SYS_OP_MASK (ESR_ELx_SYS64_ISS_SYS_MASK | \ + ESR_ELx_SYS64_ISS_DIR_MASK) /* * User space cache operations have the following sysreg encoding * in System instructions. @@ -167,6 +170,11 @@ #define ESR_ELx_SYS64_ISS_EL0_CACHE_OP_VAL \ (ESR_ELx_SYS64_ISS_SYS_VAL(1, 3, 1, 7, 0) | \ ESR_ELx_SYS64_ISS_DIR_WRITE) + +#define ESR_ELx_SYS64_ISS_SYS_CTR ESR_ELx_SYS64_ISS_SYS_VAL(3, 3, 1, 0, 0) +#define ESR_ELx_SYS64_ISS_SYS_CTR_READ (ESR_ELx_SYS64_ISS_SYS_CTR | \ + ESR_ELx_SYS64_ISS_DIR_READ) + #ifndef __ASSEMBLY__ #include diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h index e91aef2bb33d..7e4ecd1d2ac9 100644 --- a/arch/arm64/include/asm/sysreg.h +++ b/arch/arm64/include/asm/sysreg.h @@ -100,6 +100,7 @@ /* SCTLR_EL1 specific flags. */ #define SCTLR_EL1_UCI (1 << 26) #define SCTLR_EL1_SPAN (1 << 23) +#define SCTLR_EL1_UCT (1 << 15) #define SCTLR_EL1_SED (1 << 8) #define SCTLR_EL1_CP15BEN (1 << 5) diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c index 05070b72fc28..4a2f0f0fef32 100644 --- a/arch/arm64/kernel/asm-offsets.c +++ b/arch/arm64/kernel/asm-offsets.c @@ -23,6 +23,7 @@ #include #include #include +#include #include #include #include @@ -145,5 +146,6 @@ int main(void) DEFINE(HIBERN_PBE_ORIG, offsetof(struct pbe, orig_address)); DEFINE(HIBERN_PBE_ADDR, offsetof(struct pbe, address)); DEFINE(HIBERN_PBE_NEXT, offsetof(struct pbe, next)); + DEFINE(ARM64_FTR_SYSVAL, offsetof(struct arm64_ftr_reg, sys_val)); return 0; } diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c index 5836b3df0094..0150394f4cab 100644 --- a/arch/arm64/kernel/cpu_errata.c +++ b/arch/arm64/kernel/cpu_errata.c @@ -30,6 +30,21 @@ is_affected_midr_range(const struct arm64_cpu_capabilities *entry, int scope) entry->midr_range_max); } +static bool +has_mismatched_cache_line_size(const struct arm64_cpu_capabilities *entry, + int scope) +{ + WARN_ON(scope != SCOPE_LOCAL_CPU || preemptible()); + return (read_cpuid_cachetype() & arm64_ftr_reg_ctrel0.strict_mask) != + (arm64_ftr_reg_ctrel0.sys_val & arm64_ftr_reg_ctrel0.strict_mask); +} + +static void cpu_enable_trap_ctr_access(void *__unused) +{ + /* Clear SCTLR_EL1.UCT */ + config_sctlr_el1(SCTLR_EL1_UCT, 0); +} + #define MIDR_RANGE(model, min, max) \ .def_scope = SCOPE_LOCAL_CPU, \ .matches = is_affected_midr_range, \ @@ -107,6 +122,13 @@ const struct arm64_cpu_capabilities arm64_errata[] = { MIDR_RANGE(MIDR_THUNDERX_81XX, 0x00, 0x00), }, #endif + { + .desc = "Mismatched cache line size", + .capability = ARM64_MISMATCHED_CACHE_LINE_SIZE, + .matches = has_mismatched_cache_line_size, + .def_scope = SCOPE_LOCAL_CPU, + .enable = cpu_enable_trap_ctr_access, + }, { } }; diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index 224f64eddd93..93445f8b530c 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -480,6 +480,14 @@ static void user_cache_maint_handler(unsigned int esr, struct pt_regs *regs) regs->pc += 4; } +static void ctr_read_handler(unsigned int esr, struct pt_regs *regs) +{ + int rt = (esr & ESR_ELx_SYS64_ISS_RT_MASK) >> ESR_ELx_SYS64_ISS_RT_SHIFT; + + regs->regs[rt] = arm64_ftr_reg_ctrel0.sys_val; + regs->pc += 4; +} + struct sys64_hook { unsigned int esr_mask; unsigned int esr_val; @@ -492,6 +500,12 @@ static struct sys64_hook sys64_hooks[] = { .esr_val = ESR_ELx_SYS64_ISS_EL0_CACHE_OP_VAL, .handler = user_cache_maint_handler, }, + { + /* Trap read access to CTR_EL0 */ + .esr_mask = ESR_ELx_SYS64_ISS_SYS_OP_MASK, + .esr_val = ESR_ELx_SYS64_ISS_SYS_CTR_READ, + .handler = ctr_read_handler, + }, {}, }; -- 2.30.2