arm64: Allow a capability to be checked on a single CPU

Now that the capabilities are only available once all the CPUs
have booted, we're unable to check for a particular feature
in any subsystem that gets initialized before then.

In order to support this, introduce a local_cpu_has_cap() function
that tests for the presence of a given capability independently
of the whole framework.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
[ Added preemptible() check ]
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
[will: remove duplicate initialisation of caps in this_cpu_has_cap]
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 54abd9bd5c95..2b09dc477178 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1010,6 +1010,24 @@ static void __init setup_feature_capabilities(void)
 	enable_cpu_capabilities(arm64_features);
 }
 
+/*
+ * Check if the current CPU has a given feature capability.
+ * Should be called from non-preemptible context.
+ */
+bool this_cpu_has_cap(unsigned int cap)
+{
+	const struct arm64_cpu_capabilities *caps;
+
+	if (WARN_ON(preemptible()))
+		return false;
+
+	for (caps = arm64_features; caps->desc; caps++)
+		if (caps->capability == cap && caps->matches)
+			return caps->matches(caps, SCOPE_LOCAL_CPU);
+
+	return false;
+}
+
 void __init setup_cpu_features(void)
 {
 	u32 cwg;