[Xen-devel] [PATCH 08/22] xen/arm: p2m: Simplify p2m type check by using bitmask

[Julien Grall <julien.grall@xxxxxxx>]

The resulting assembly code for the macros is much simpler and will
never contain more than one instruction branch.

The idea is taken from x86 (see include/asm-x86/p2m.h). Also move the
two helpers earlier to keep all the p2m type definitions together.

Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
---
 xen/include/asm-arm/p2m.h | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/xen/include/asm-arm/p2m.h b/xen/include/asm-arm/p2m.h
index dbbcefe..3091c04 100644
--- a/xen/include/asm-arm/p2m.h
+++ b/xen/include/asm-arm/p2m.h
@@ -97,6 +97,17 @@ typedef enum {
     p2m_max_real_type,  /* Types after this won't be store in the p2m */
 } p2m_type_t;
 
+/* We use bitmaps and mask to handle groups of types */
+#define p2m_to_mask(_t) (1UL << (_t))
+
+/* RAM types, which map to real machine frames */
+#define P2M_RAM_TYPES (p2m_to_mask(p2m_ram_rw) |        \
+                       p2m_to_mask(p2m_ram_ro))
+
+/* Useful predicates */
+#define p2m_is_ram(_t) (p2m_to_mask(_t) & P2M_RAM_TYPES)
+#define p2m_is_foreign(_t) (p2m_to_mask(_t) & p2m_to_mask(p2m_map_foreign))
+
 static inline
 void p2m_mem_access_emulate_check(struct vcpu *v,
                                   const vm_event_response_t *rsp)
@@ -110,9 +121,6 @@ void p2m_altp2m_check(struct vcpu *v, uint16_t idx)
     /* Not supported on ARM. */
 }
 
-#define p2m_is_foreign(_t)  ((_t) == p2m_map_foreign)
-#define p2m_is_ram(_t)      ((_t) == p2m_ram_rw || (_t) == p2m_ram_ro)
-
 /* Initialise vmid allocator */
 void p2m_vmid_allocator_init(void);
 
-- 
1.9.1


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