diff options
Diffstat (limited to 'arch/arm64/kernel/cpufeature.c')
| -rw-r--r-- | arch/arm64/kernel/cpufeature.c | 36 |
1 files changed, 36 insertions, 0 deletions
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 515975f42d03..bdabfc98226a 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -2056,6 +2056,34 @@ static bool can_use_gic_priorities(const struct arm64_cpu_capabilities *entry, return enable_pseudo_nmi; } + +static bool has_gic_prio_relaxed_sync(const struct arm64_cpu_capabilities *entry, + int scope) +{ + /* + * If we're not using priority masking then we won't be poking PMR_EL1, + * and there's no need to relax synchronization of writes to it, and + * ICC_CTLR_EL1 might not be accessible and we must avoid reads from + * that. + * + * ARM64_HAS_GIC_PRIO_MASKING has a lower index, and is a boot CPU + * feature, so will be detected earlier. + */ + BUILD_BUG_ON(ARM64_HAS_GIC_PRIO_RELAXED_SYNC <= ARM64_HAS_GIC_PRIO_MASKING); + if (!cpus_have_cap(ARM64_HAS_GIC_PRIO_MASKING)) + return false; + + /* + * When Priority Mask Hint Enable (PMHE) == 0b0, PMR is not used as a + * hint for interrupt distribution, a DSB is not necessary when + * unmasking IRQs via PMR, and we can relax the barrier to a NOP. + * + * Linux itself doesn't use 1:N distribution, so has no need to + * set PMHE. The only reason to have it set is if EL3 requires it + * (and we can't change it). + */ + return (gic_read_ctlr() & ICC_CTLR_EL1_PMHE_MASK) == 0; +} #endif #ifdef CONFIG_ARM64_BTI @@ -2546,6 +2574,14 @@ static const struct arm64_cpu_capabilities arm64_features[] = { .type = ARM64_CPUCAP_STRICT_BOOT_CPU_FEATURE, .matches = can_use_gic_priorities, }, + { + /* + * Depends on ARM64_HAS_GIC_PRIO_MASKING + */ + .capability = ARM64_HAS_GIC_PRIO_RELAXED_SYNC, + .type = ARM64_CPUCAP_STRICT_BOOT_CPU_FEATURE, + .matches = has_gic_prio_relaxed_sync, + }, #endif #ifdef CONFIG_ARM64_E0PD { |