arm64: Detect FEAT_XNX

Detect the feature in anticipation of using it in KVM.

Reviewed-by: Marc Zyngier <maz@kernel.org>
Tested-by: Marc Zyngier <maz@kernel.org>
Link: https://msgid.link/20251124190158.177318-2-oupton@kernel.org
Signed-off-by: Oliver Upton <oupton@kernel.org>

arch/arm64/kernel/cpufeature.c

@@ -3088,6 +3088,13 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.capability = ARM64_HAS_GICV5_LEGACY,
 		.matches = test_has_gicv5_legacy,
 	},
+	{
+		.desc = "XNX",
+		.capability = ARM64_HAS_XNX,
+		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+		.matches = has_cpuid_feature,
+		ARM64_CPUID_FIELDS(ID_AA64MMFR1_EL1, XNX, IMP)
+	},
 	{},
 };
 

arch/arm64/tools/cpucaps

@@ -64,6 +64,7 @@ HAS_TLB_RANGE
 HAS_VA52
 HAS_VIRT_HOST_EXTN
 HAS_WFXT
+HAS_XNX
 HAFT
 HW_DBM
 KVM_HVHE