On 09/07/15 10:48, Mark Rutland wrote:

On Wed, Jul 08, 2015 at 05:19:06PM +0100, Marc Zyngier wrote:

quoted

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

Nit: s/,/./

It's probably worth mentioning somewhere that we have to check CurrentEL
rather than a feature register in case some prior software dropped us to
EL1N (e.g. if we're a guest under this scheme).

Good point, this is a leftover from a previous version that actually
checked the feature register. I'll clean up the commit log.

Thanks,

	M.

Mark.

quoted

This will be used to trigger kernel patching in KVM.

Signed-off-by: Marc Zyngier <redacted>
---
 arch/arm64/include/asm/cpufeature.h |  3 ++-
 arch/arm64/kernel/cpufeature.c      | 11 +++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index c104421..6c3742d 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h

@@ -25,8 +25,9 @@
 #define ARM64_WORKAROUND_DEVICE_LOAD_ACQUIRE	1
 #define ARM64_WORKAROUND_845719			2
 #define ARM64_HAS_SYSREG_GIC_CPUIF		3
+#define ARM64_HAS_VIRT_HOST_EXTN		4
 
-#define ARM64_NCAPS				4
+#define ARM64_NCAPS				5
 
 #ifndef __ASSEMBLY__
 

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 5ad86ce..e1dcd63 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c

@@ -21,6 +21,7 @@
 #include <linux/types.h>
 #include <asm/cpu.h>
 #include <asm/cpufeature.h>
+#include <asm/virt.h>
 
 static bool
 has_id_aa64pfr0_feature(const struct arm64_cpu_capabilities *entry)

@@ -31,6 +32,11 @@ has_id_aa64pfr0_feature(const struct arm64_cpu_capabilities *entry)
 	return (val & entry->register_mask) == entry->register_value;
 }
 
+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",

@@ -39,6 +45,11 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.register_mask = (0xf << 24),
 		.register_value = (1 << 24),
 	},
+	{
+		.desc = "Virtualization Host Extensions",
+		.capability = ARM64_HAS_VIRT_HOST_EXTN,
+		.matches = runs_at_el2,
+	},
 	{},
 };
 

-- 
2.1.4

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