update_headers.sh: arm64: Copy sve_context.h if available

The SVE KVM support for arm64 includes the additional backend
header <asm/sve_context.h> from <asm/kvm.h>.

So update this header if it is available.

To avoid creating a sudden dependency on a specific minimum kernel
version, ignore such optional headers if the source kernel tree
doesn't have them.
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

util/update_headers.sh

@@ -25,11 +25,23 @@ fi
 
 cp -- "$LINUX_ROOT/include/uapi/linux/kvm.h" include/linux
 
+unset KVMTOOL_PATH
+
+copy_optional_arch () {
+	local src="$LINUX_ROOT/arch/$arch/include/uapi/$1"
+
+	if [ -r "$src" ]
+	then
+		cp -- "$src" "$KVMTOOL_PATH/include/asm/"
+	fi
+}
+
 for arch in arm arm64 mips powerpc x86
 do
 	case "$arch" in
 		arm) KVMTOOL_PATH=arm/aarch32 ;;
-		arm64) KVMTOOL_PATH=arm/aarch64 ;;
+		arm64)	KVMTOOL_PATH=arm/aarch64
+			copy_optional_arch asm/sve_context.h ;;
 		*) KVMTOOL_PATH=$arch ;;
 	esac
 	cp -- "$LINUX_ROOT/arch/$arch/include/uapi/asm/kvm.h" \