[PATCH 5/7] arm64: capabilities: Optimize this_cpu_has_cap

Suzuki K Poulose
2018-11-05T11:55:15Z

Make use of the sorted capability list to access the capability
entry in this_cpu_has_cap() to avoid iterating over the two
tables.

Cc: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
arch/arm64/kernel/cpufeature.c | 31 +++++++++----------------------
1 file changed, 9 insertions(+), 22 deletions(-)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 7e9ebbe..96e687e 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1508,25 +1508,6 @@ static void __init setup_elf_hwcaps(const struct arm64_cpu_capabilities *hwcaps)
cap_set_elf_hwcap(hwcaps);
}

-/*
- * Check if the current CPU has a given feature capability.
- * Should be called from non-preemptible context.
- */
-static bool __this_cpu_has_cap(const struct arm64_cpu_capabilities *cap_array,
- unsigned int cap)
-{
- const struct arm64_cpu_capabilities *caps;
-
- if (WARN_ON(preemptible()))
- return false;
-
- for (caps = cap_array; caps->matches; caps++)
- if (caps->capability == cap)
- return caps->matches(caps, SCOPE_LOCAL_CPU);
-
- return false;
-}
-
static void __update_cpu_capabilities(const struct arm64_cpu_capabilities *caps,
u16 scope_mask, const char *info)
{
@@ -1776,10 +1757,16 @@ static void __init mark_const_caps_ready(void)
static_branch_enable(&arm64_const_caps_ready);
}

-bool this_cpu_has_cap(unsigned int cap)
+bool this_cpu_has_cap(unsigned int n)
{
- return (__this_cpu_has_cap(arm64_features, cap) ||
- __this_cpu_has_cap(arm64_errata, cap));
+ if (!WARN_ON(preemptible()) && n < ARM64_NCAPS) {
+ const struct arm64_cpu_capabilities *cap = cpu_hwcaps_ptrs[n];
+
+ if (cap)
+ return cap->matches(cap, SCOPE_LOCAL_CPU);
+ }
+
+ return false;
}

static void __init setup_system_capabilities(void)
--
2.7.4