arm64: Add ARM64_HAS_VIRT_HOST_EXTN feature

Add a new ARM64_HAS_VIRT_HOST_EXTN features to indicate that the
CPU has the ARMv8.1 VHE capability.

This will be used to trigger kernel patching in KVM.
Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

arch/arm64/include/asm/cpufeature.h

@@ -30,8 +30,12 @@
 #define ARM64_HAS_LSE_ATOMICS			5
 #define ARM64_WORKAROUND_CAVIUM_23154		6
 #define ARM64_WORKAROUND_834220			7
+/* #define ARM64_HAS_NO_HW_PREFETCH		8 */
+/* #define ARM64_HAS_UAO			9 */
+/* #define ARM64_ALT_PAN_NOT_UAO		10 */
+#define ARM64_HAS_VIRT_HOST_EXTN		11
 
-#define ARM64_NCAPS				8
+#define ARM64_NCAPS				12
 
 #ifndef __ASSEMBLY__
 

arch/arm64/kernel/cpufeature.c

@@ -26,6 +26,7 @@
 #include <asm/cpu_ops.h>
 #include <asm/processor.h>
 #include <asm/sysreg.h>
+#include <asm/virt.h>
 
 unsigned long elf_hwcap __read_mostly;
 EXPORT_SYMBOL_GPL(elf_hwcap);
@@ -621,6 +622,11 @@ static bool has_useable_gicv3_cpuif(const struct arm64_cpu_capabilities *entry)
 	return has_sre;
 }
 
+static bool runs_at_el2(const struct arm64_cpu_capabilities *entry)
+{
+	return is_kernel_in_hyp_mode();
+}
+
 static const struct arm64_cpu_capabilities arm64_features[] = {
 	{
 		.desc = "GIC system register CPU interface",
@@ -651,6 +657,11 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.min_field_value = 2,
 	},
 #endif /* CONFIG_AS_LSE && CONFIG_ARM64_LSE_ATOMICS */
+	{
+		.desc = "Virtualization Host Extensions",
+		.capability = ARM64_HAS_VIRT_HOST_EXTN,
+		.matches = runs_at_el2,
+	},
 	{},
 };