[Xen-devel] [PATCH v2 1/3] x86/mm: short-circuit HVM-only mode flags when !HVM

["Jan Beulich" <JBeulich@xxxxxxxx>]

#define-ing them to zero allows better code generation in this case,
and paves the way for more DCE, allowing to leave certain functions just
declared, but not defined.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
v2: New.

--- a/xen/arch/x86/mm/paging.c
+++ b/xen/arch/x86/mm/paging.c
@@ -837,7 +837,9 @@ int paging_enable(struct domain *d, u32
     switch ( mode & (PG_external | PG_translate | PG_refcounts) )
     {
     case 0:
+#if PG_external | PG_translate | PG_refcounts
     case PG_external | PG_translate | PG_refcounts:
+#endif
         break;
     default:
         return -EINVAL;
--- a/xen/include/asm-x86/paging.h
+++ b/xen/include/asm-x86/paging.h
@@ -46,19 +46,29 @@
 #define PG_SH_enable   0
 #define PG_SH_forced   0
 #endif
+#ifdef CONFIG_HVM
 #define PG_HAP_enable  (1U << PG_HAP_shift)
+#else
+#define PG_HAP_enable  0
+#endif
 
 /* common paging mode bits */
 #define PG_mode_shift  10 
+#ifdef CONFIG_HVM
 /* Refcounts based on shadow tables instead of guest tables */
 #define PG_refcounts   (XEN_DOMCTL_SHADOW_ENABLE_REFCOUNT << PG_mode_shift)
-/* Enable log dirty mode */
-#define PG_log_dirty   (XEN_DOMCTL_SHADOW_ENABLE_LOG_DIRTY << PG_mode_shift)
 /* Xen does p2m translation, not guest */
 #define PG_translate   (XEN_DOMCTL_SHADOW_ENABLE_TRANSLATE << PG_mode_shift)
 /* Xen does not steal address space from the domain for its own booking;
  * requires VT or similar mechanisms */
 #define PG_external    (XEN_DOMCTL_SHADOW_ENABLE_EXTERNAL << PG_mode_shift)
+#else
+#define PG_refcounts   0
+#define PG_translate   0
+#define PG_external    0
+#endif
+/* Enable log dirty mode */
+#define PG_log_dirty   (XEN_DOMCTL_SHADOW_ENABLE_LOG_DIRTY << PG_mode_shift)
 
 /* All paging modes. */
 #define PG_MASK (PG_refcounts | PG_log_dirty | PG_translate | PG_external)





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