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

Marc Zyngier · wildea01 · commit e3661b128e53 · 2016-04-25T15:13:05.000+01:00
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 &lt;catalin.marinas@arm.com&gt;
Signed-off-by: Marc Zyngier &lt;marc.zyngier@arm.com&gt;
[ Added preemptible() check ]
Signed-off-by: Suzuki K Poulose &lt;suzuki.poulose@arm.com&gt;
[will: remove duplicate initialisation of caps in this_cpu_has_cap]
Signed-off-by: Will Deacon &lt;will.deacon@arm.com&gt;
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
@@ -109,6 +109,8 @@ struct arm64_cpu_capabilities {
 
 extern DECLARE_BITMAP(cpu_hwcaps, ARM64_NCAPS);
 
+bool this_cpu_has_cap(unsigned int cap);
+
 static inline bool cpu_have_feature(unsigned int num)
 {
 	return elf_hwcap & (1UL << num);
diff --git 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;

Original file line number	Diff line number	Diff line change
`@@ -109,6 +109,8 @@ struct arm64_cpu_capabilities {`
`109`	`109`
`110`	`110`	`extern DECLARE_BITMAP(cpu_hwcaps, ARM64_NCAPS);`
`111`	`111`
	`112`	`+bool this_cpu_has_cap(unsigned int cap);`
	`113`	`+`
`112`	`114`	`static inline bool cpu_have_feature(unsigned int num)`
`113`	`115`	`{`
`114`	`116`	`return elf_hwcap & (1UL << num);`