From: Xie XiuQi xiexiuqi@huawei.com

hulk inclusion category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I4JBSJ CVE: NA

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LSE atomic instruction might introduce performance regression on specific benchmark or business. So add a cmdline option to disable/enable it.

"lse=off" cmdline option means disable LSE atomic instruction.

Signed-off-by: Xie XiuQi xiexiuqi@huawei.com [liwei: Fix compile warning with CONFIG_ARM64_LSE_ATOMICS=n] Signed-off-by: Wei Li liwei391@huawei.com --- arch/arm64/kernel/cpufeature.c | 32 +++++++++++++++++++++++++++++++- 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 3517dd2b0358..6d12bbc54728 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -1431,6 +1431,22 @@ u64 __read_sysreg_by_encoding(u32 sys_id)

#include <linux/irqchip/arm-gic-v3.h>

+#ifdef CONFIG_ARM64_LSE_ATOMICS +static bool lse_disabled; + +static int __init parse_lse(char *str) +{ + if (str == NULL) + return 1; + + if (!strncmp(str, "off", 3)) + lse_disabled = true; + + return 0; +} +early_param("lse", parse_lse); +#endif + static bool has_always(const struct arm64_cpu_capabilities *entry, int scope) { @@ -1539,6 +1555,20 @@ static bool has_32bit_el0(const struct arm64_cpu_capabilities *entry, int scope) return true; }

+#ifdef CONFIG_ARM64_LSE_ATOMICS +static bool has_cpuid_feature_lse(const struct arm64_cpu_capabilities *entry, + int scope) +{ + if (lse_disabled) { + pr_info_once("%s forced OFF by command line option\n", + entry->desc); + return false; + } + + return has_cpuid_feature(entry, scope); +} +#endif + static bool has_useable_gicv3_cpuif(const struct arm64_cpu_capabilities *entry, int scope) { bool has_sre; @@ -2316,7 +2346,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = { .desc = "LSE atomic instructions", .capability = ARM64_HAS_LSE_ATOMICS, .type = ARM64_CPUCAP_SYSTEM_FEATURE, - .matches = has_cpuid_feature, + .matches = has_cpuid_feature_lse, ARM64_CPUID_FIELDS(ID_AA64ISAR0_EL1, ATOMIC, IMP) }, #endif /* CONFIG_ARM64_LSE_ATOMICS */