[PATCH v6 20/30] arm64: cpufeature: Add helper to directly probe CPU for POE support

[Kevin Brodsky]

In order to support the kpkeys_hardened_pgtables feature, we will
need to decide how to allocate early page tables, before boot CPU
features have been detected. To that end, add a new helper to check
that the boot CPU supports POE (meaning POE will eventually be
enabled).

Signed-off-by: Kevin Brodsky <kevin.brodsky at arm.com>
---
 arch/arm64/include/asm/cpufeature.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 4de51f8d92cb..8722e9e62702 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -1078,6 +1078,18 @@ static inline bool cpu_has_lpa2(void)
 #endif
 }
 
+static inline bool cpu_has_poe(void)
+{
+	u64 mmfr3;
+
+	if (!IS_ENABLED(CONFIG_ARM64_POE))
+		return false;
+
+	mmfr3 = read_sysreg_s(SYS_ID_AA64MMFR3_EL1);
+	return cpuid_feature_extract_unsigned_field(mmfr3,
+						    ID_AA64MMFR3_EL1_S1POE_SHIFT);
+}
+
 #endif /* __ASSEMBLER__ */
 
 #endif
-- 
2.51.2