livepatch: x86, ARM, alternative: Expose FEATURE_LIVEPATCH

To use as a common way of testing alternative patching for
livepatches. Both architectures have this FEATURE and the
test-cases can piggyback on that.

Reviewed-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Acked-by: Julien Grall <julien.grall@arm.com>
Suggested-by: Julien Grall <julien.grall@arm.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

xen/arch/arm/livepatch.c

@@ -8,6 +8,7 @@
 #include <xen/livepatch.h>
 #include <xen/vmap.h>
 
+#include <asm/cpufeature.h>
 #include <asm/livepatch.h>
 #include <asm/mm.h>
 
@@ -161,6 +162,8 @@ void __init arch_livepatch_init(void)
     end = (void *)LIVEPATCH_VMAP_END;
 
     vm_init_type(VMAP_XEN, start, end);
+
+    cpus_set_cap(LIVEPATCH_FEATURE);
 }
 
 /*

xen/include/asm-arm/cpufeature.h

@@ -39,8 +39,9 @@
 #define ARM64_WORKAROUND_DEVICE_LOAD_ACQUIRE    1
 #define ARM32_WORKAROUND_766422 2
 #define ARM64_WORKAROUND_834220 3
+#define LIVEPATCH_FEATURE   4
 
-#define ARM_NCAPS           4
+#define ARM_NCAPS           5
 
 #ifndef __ASSEMBLY__
 

xen/include/asm-x86/livepatch.h

@@ -10,6 +10,7 @@
 
 #define ARCH_PATCH_INSN_SIZE 5
 #define ARCH_LIVEPATCH_RANGE SZ_2G
+#define LIVEPATCH_FEATURE    X86_FEATURE_ALWAYS
 
 #endif /* __XEN_X86_LIVEPATCH_H__ */
 

xen/test/livepatch/xen_hello_world_func.c

@@ -6,6 +6,7 @@
 #include <xen/types.h>
 
 #include <asm/alternative.h>
+#include <asm/livepatch.h>
 #include <asm/nops.h>
 #include <asm/uaccess.h>
 
@@ -17,7 +18,7 @@ const char *xen_hello_world(void)
     unsigned long tmp;
     int rc;
 
-    alternative(ASM_NOP8, ASM_NOP1, X86_FEATURE_LM);
+    alternative(ASM_NOP8, ASM_NOP1, LIVEPATCH_FEATURE);
     /*
      * Any BUG, or WARN_ON will contain symbol and payload name. Furthermore
      * exceptions will be caught and processed properly.