xen: add return value to set_phys_to_machine()

set_phys_to_machine() can return false on failure, which means a memory
allocation failure for the p2m structure.  It can only fail if setting
the mfn for a pfn in previously unused address space.  It is guaranteed
to succeed if you're setting a mapping to INVALID_P2M_ENTRY or updating
the mfn for an existing pfn.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

2 files changed, 9 insertions, 6 deletions

diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index bf5f7d32bd08..e40ca6e67bb5 100644
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -37,7 +37,7 @@ typedef struct xpaddr {
 
 
 extern unsigned long get_phys_to_machine(unsigned long pfn);
-extern void set_phys_to_machine(unsigned long pfn, unsigned long mfn);
+extern bool set_phys_to_machine(unsigned long pfn, unsigned long mfn);
 
 static inline unsigned long pfn_to_mfn(unsigned long pfn)
 {
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index d4c7265cf0a0..b96513437236 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -282,7 +282,7 @@ static void p2m_init(unsigned long *p2m)
  */
 void xen_build_mfn_list_list(void)
 {
-        unsigned pfn, i;
+        unsigned pfn;
 
         /* Pre-initialize p2m_top_mfn to be completely missing */
         if (p2m_top_mfn == NULL) {
@@ -496,19 +496,22 @@ bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
         return true;
 }
 
-void set_phys_to_machine(unsigned long pfn, unsigned long mfn)
+bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 {
         if (unlikely(xen_feature(XENFEAT_auto_translated_physmap))) {
                 BUG_ON(pfn != mfn && mfn != INVALID_P2M_ENTRY);
-                return;
+                return true;
         }
 
         if (unlikely(!__set_phys_to_machine(pfn, mfn)))  {
-                WARN(!alloc_p2m(pfn), "Can't allocate p2m for %lx, %lx", pfn, mfn);
+                if (!alloc_p2m(pfn))
+                        return false;
 
                 if (!__set_phys_to_machine(pfn, mfn))
-                        BUG();
+                        return false;
         }
+
+        return true;
 }
 
 unsigned long arbitrary_virt_to_mfn(void *vaddr)