gistfile1.txt

diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c                                                    
index 1b267e7..2a6f677 100644                                                                           
--- a/arch/x86/xen/p2m.c                                                                                
+++ b/arch/x86/xen/p2m.c                                                                                
@@ -724,7 +724,9 @@ int m2p_add_override(unsigned long mfn, struct page *page,                          
        return 0;                                                                                       
 }                                                                                                      
 EXPORT_SYMBOL_GPL(m2p_add_override);                                                                   
-int m2p_remove_override(struct page *page, bool clear_pte)                                             
+int m2p_remove_override(struct page *page, bool clear_pte,                                             
+                       uint64_t host_addr, uint64_t dev_bus_addr,                                      
+                       grant_handle_t handle)                                                          
 {                                                                                                      
        unsigned long flags;                                                                            
        unsigned long mfn;                                                                              
@@ -754,9 +756,16 @@ int m2p_remove_override(struct page *page, bool clear_pte)                         
        ClearPagePrivate(page);                                                                         
                                                                                                        
        if (clear_pte) {                                                                                
+               int retrieve_map_op = !(host_addr != ~0ULL && handle != ~0UL &&                         
+                                       dev_bus_addr != ~0ULL);                                         
                struct gnttab_map_grant_ref *map_op =                                                   
                        (struct gnttab_map_grant_ref *) page->index;                                    
-               set_phys_to_machine(pfn, map_op->dev_bus_addr);                                         
+                                                                                                       
+               if (!retrieve_map_op)                                                                   
+                       set_phys_to_machine(pfn, dev_bus_addr);                                         
+               else                                                                                    
+                       set_phys_to_machine(pfn, map_op->dev_bus_addr);                                 
+                                                                                                       
                if (!PageHighMem(page)) {                                                               
                        struct multicall_space mcs;                                                     
                        struct gnttab_unmap_grant_ref *unmap_op;                                        
@@ -768,7 +777,7 @@ int m2p_remove_override(struct page *page, bool clear_pte)                          
                         * issued. In this case handle is going to -1 because                           
                         * it hasn't been modified yet.                                                 
                         */                                                                             
-                       if (map_op->handle == -1)                                                       
+                       if (retrieve_map_op && map_op->handle == -1)                                    
                                xen_mc_flush();                                                         
                        /*                                                                              
                         * Now if map_op->handle is negative it means that the                          
@@ -784,8 +793,13 @@ int m2p_remove_override(struct page *page, bool clear_pte)                         
                        mcs = xen_mc_entry(                                                             
                                        sizeof(struct gnttab_unmap_grant_ref));                         
                        unmap_op = mcs.args;                                                            
-                       unmap_op->host_addr = map_op->host_addr;                                        
-                       unmap_op->handle = map_op->handle;                                              
+                       if (!retrieve_map_op) {                                                         
+                               unmap_op->host_addr = host_addr;                                        
+                               unmap_op->handle = handle;                                              
+                       } else {                                                                        
+                               unmap_op->host_addr = map_op->host_addr;                                
+                               unmap_op->handle = map_op->handle;                                      
+                       }                                                                               
                        unmap_op->dev_bus_addr = 0;                                                     
                                                                                                        
                        MULTI_grant_table_op(mcs.mc,