[PATCH] domain_page: handle NULL within unmap_domain_page() itself

[Hongyan Xia <hx242@xxxxxxx>]

From: Hongyan Xia <hongyxia@xxxxxxxxxx>

The macro version UNMAP_DOMAIN_PAGE() does both NULL checking and
variable clearing. Move NULL checking into the function itself so that
the semantics is consistent with other similar constructs like XFREE().
This also eases the use unmap_domain_page() in error handling paths,
where we only care about NULL checking but not about variable clearing.

Signed-off-by: Hongyan Xia <hongyxia@xxxxxxxxxx>
---
 xen/arch/arm/mm.c             | 3 +++
 xen/arch/x86/domain_page.c    | 2 +-
 xen/include/xen/domain_page.h | 7 ++-----
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 727107eefa..1b14f49345 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -498,6 +498,9 @@ void unmap_domain_page(const void *va)
     lpae_t *map = this_cpu(xen_dommap);
     int slot = ((unsigned long) va - DOMHEAP_VIRT_START) >> SECOND_SHIFT;
 
+    if ( !va )
+        return;
+
     local_irq_save(flags);
 
     ASSERT(slot >= 0 && slot < DOMHEAP_ENTRIES);
diff --git a/xen/arch/x86/domain_page.c b/xen/arch/x86/domain_page.c
index dd32712d2f..b03728e18e 100644
--- a/xen/arch/x86/domain_page.c
+++ b/xen/arch/x86/domain_page.c
@@ -181,7 +181,7 @@ void unmap_domain_page(const void *ptr)
     unsigned long va = (unsigned long)ptr, mfn, flags;
     struct vcpu_maphash_entry *hashent;
 
-    if ( va >= DIRECTMAP_VIRT_START )
+    if ( !va || va >= DIRECTMAP_VIRT_START )
         return;
 
     ASSERT(va >= MAPCACHE_VIRT_START && va < MAPCACHE_VIRT_END);
diff --git a/xen/include/xen/domain_page.h b/xen/include/xen/domain_page.h
index ab2be7b719..a182d33b67 100644
--- a/xen/include/xen/domain_page.h
+++ b/xen/include/xen/domain_page.h
@@ -73,11 +73,8 @@ static inline void unmap_domain_page_global(const void *va) 
{};
 #endif /* !CONFIG_DOMAIN_PAGE */
 
 #define UNMAP_DOMAIN_PAGE(p) do {   \
-    if ( p )                        \
-    {                               \
-        unmap_domain_page(p);       \
-        (p) = NULL;                 \
-    }                               \
+    unmap_domain_page(p);           \
+    (p) = NULL;                     \
 } while ( false )
 
 #endif /* __XEN_DOMAIN_PAGE_H__ */
-- 
2.17.1