x86/p2m: make p2m_alloc_ptp() return an MFN

None of the callers really needs the struct page_info pointer.

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

--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -569,7 +569,7 @@ int p2m_set_entry(struct p2m_domain *p2m
     return rc;
 }
 
-struct page_info *p2m_alloc_ptp(struct p2m_domain *p2m, unsigned long type)
+mfn_t p2m_alloc_ptp(struct p2m_domain *p2m, unsigned long type)
 {
     struct page_info *pg;
 
@@ -577,13 +577,13 @@ struct page_info *p2m_alloc_ptp(struct p
     ASSERT(p2m->domain);
     ASSERT(p2m->domain->arch.paging.alloc_page);
     pg = p2m->domain->arch.paging.alloc_page(p2m->domain);
-    if (pg == NULL)
-        return NULL;
+    if ( !pg )
+        return INVALID_MFN;
 
     page_list_add_tail(pg, &p2m->pages);
     pg->u.inuse.type_info = type | 1 | PGT_validated;
 
-    return pg;
+    return page_to_mfn(pg);
 }
 
 void p2m_free_ptp(struct p2m_domain *p2m, struct page_info *pg)
@@ -609,7 +609,7 @@ void p2m_free_ptp(struct p2m_domain *p2m
  */
 int p2m_alloc_table(struct p2m_domain *p2m)
 {
-    struct page_info *p2m_top;
+    mfn_t top_mfn;
     struct domain *d = p2m->domain;
     int rc = 0;
 
@@ -632,14 +632,14 @@ int p2m_alloc_table(struct p2m_domain *p
 
     P2M_PRINTK("allocating p2m table\n");
 
-    p2m_top = p2m_alloc_ptp(p2m, PGT_l4_page_table);
-    if ( p2m_top == NULL )
+    top_mfn = p2m_alloc_ptp(p2m, PGT_l4_page_table);
+    if ( mfn_eq(top_mfn, INVALID_MFN) )
     {
         p2m_unlock(p2m);
         return -ENOMEM;
     }
 
-    p2m->phys_table = pagetable_from_mfn(page_to_mfn(p2m_top));
+    p2m->phys_table = pagetable_from_mfn(top_mfn);
 
     if ( hap_enabled(d) )
         iommu_share_p2m_table(d);
--- a/xen/arch/x86/mm/p2m-ept.c
+++ b/xen/arch/x86/mm/p2m-ept.c
@@ -225,16 +225,16 @@ static void ept_p2m_type_to_flags(struct
 /* Fill in middle levels of ept table */
 static int ept_set_middle_entry(struct p2m_domain *p2m, ept_entry_t *ept_entry)
 {
-    struct page_info *pg;
+    mfn_t mfn;
     ept_entry_t *table;
     unsigned int i;
 
-    pg = p2m_alloc_ptp(p2m, 0);
-    if ( pg == NULL )
+    mfn = p2m_alloc_ptp(p2m, 0);
+    if ( mfn_eq(mfn, INVALID_MFN) )
         return 0;
 
     ept_entry->epte = 0;
-    ept_entry->mfn = page_to_mfn(pg);
+    ept_entry->mfn = mfn_x(mfn);
     ept_entry->access = p2m->default_access;
 
     ept_entry->r = ept_entry->w = ept_entry->x = 1;
@@ -243,7 +243,7 @@ static int ept_set_middle_entry(struct p
 
     ept_entry->suppress_ve = 1;
 
-    table = __map_domain_page(pg);
+    table = map_domain_page(mfn);
 
     for ( i = 0; i < EPT_PAGETABLE_ENTRIES; i++ )
         table[i].suppress_ve = 1;
--- a/xen/arch/x86/mm/p2m-pt.c
+++ b/xen/arch/x86/mm/p2m-pt.c
@@ -195,7 +195,7 @@ p2m_next_level(struct p2m_domain *p2m, v
     l1_pgentry_t *p2m_entry;
     l1_pgentry_t new_entry;
     void *next;
-    struct page_info *pg;
+    mfn_t mfn;
     unsigned int i, flags;
     unsigned long pfn;
 
@@ -206,12 +206,11 @@ p2m_next_level(struct p2m_domain *p2m, v
     /* PoD/paging: Not present doesn't imply empty. */
     if ( !l1e_get_flags(*p2m_entry) )
     {
-        pg = p2m_alloc_ptp(p2m, type);
-        if ( pg == NULL )
+        mfn = p2m_alloc_ptp(p2m, type);
+        if ( mfn_eq(mfn, INVALID_MFN) )
             return -ENOMEM;
 
-        new_entry = l1e_from_pfn(mfn_x(page_to_mfn(pg)),
-                                 P2M_BASE_FLAGS | _PAGE_RW);
+        new_entry = l1e_from_pfn(mfn_x(mfn), P2M_BASE_FLAGS | _PAGE_RW);
 
         switch ( type ) {
         case PGT_l3_page_table:
@@ -239,11 +238,11 @@ p2m_next_level(struct p2m_domain *p2m, v
     /* split 1GB pages into 2MB pages */
     if ( type == PGT_l2_page_table && (flags & _PAGE_PSE) )
     {
-        pg = p2m_alloc_ptp(p2m, PGT_l2_page_table);
-        if ( pg == NULL )
+        mfn = p2m_alloc_ptp(p2m, PGT_l2_page_table);
+        if ( mfn_eq(mfn, INVALID_MFN) )
             return -ENOMEM;
 
-        l1_entry = __map_domain_page(pg);
+        l1_entry = map_domain_page(mfn);
         for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++ )
         {
             new_entry = l1e_from_pfn(pfn | (i * L1_PAGETABLE_ENTRIES), flags);
@@ -251,8 +250,7 @@ p2m_next_level(struct p2m_domain *p2m, v
             p2m->write_p2m_entry(p2m, gfn, l1_entry + i, new_entry, 2);
         }
         unmap_domain_page(l1_entry);
-        new_entry = l1e_from_pfn(mfn_x(page_to_mfn(pg)),
-                                 P2M_BASE_FLAGS | _PAGE_RW); /* disable PSE */
+        new_entry = l1e_from_pfn(mfn_x(mfn), P2M_BASE_FLAGS | _PAGE_RW);
         p2m_add_iommu_flags(&new_entry, 2, IOMMUF_readable|IOMMUF_writable);
         p2m->write_p2m_entry(p2m, gfn, p2m_entry, new_entry, 3);
     }
@@ -261,8 +259,8 @@ p2m_next_level(struct p2m_domain *p2m, v
     /* split single 2MB large page into 4KB page in P2M table */
     if ( type == PGT_l1_page_table && (flags & _PAGE_PSE) )
     {
-        pg = p2m_alloc_ptp(p2m, PGT_l1_page_table);
-        if ( pg == NULL )
+        mfn = p2m_alloc_ptp(p2m, PGT_l1_page_table);
+        if ( mfn_eq(mfn, INVALID_MFN) )
             return -ENOMEM;
 
         /* New splintered mappings inherit the flags of the old superpage, 
@@ -272,7 +270,7 @@ p2m_next_level(struct p2m_domain *p2m, v
         else
             flags &= ~_PAGE_PSE; /* Clear _PAGE_PSE (== _PAGE_PAT) */
         
-        l1_entry = __map_domain_page(pg);
+        l1_entry = map_domain_page(mfn);
         for ( i = 0; i < L1_PAGETABLE_ENTRIES; i++ )
         {
             new_entry = l1e_from_pfn(pfn | i, flags);
@@ -281,8 +279,7 @@ p2m_next_level(struct p2m_domain *p2m, v
         }
         unmap_domain_page(l1_entry);
         
-        new_entry = l1e_from_pfn(mfn_x(page_to_mfn(pg)),
-                                 P2M_BASE_FLAGS | _PAGE_RW);
+        new_entry = l1e_from_pfn(mfn_x(mfn), P2M_BASE_FLAGS | _PAGE_RW);
         p2m_add_iommu_flags(&new_entry, 1, IOMMUF_readable|IOMMUF_writable);
         p2m->write_p2m_entry(p2m, gfn, p2m_entry, new_entry, 2);
     }
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -684,7 +684,7 @@ void p2m_mem_paging_resume(struct domain
  * Internal functions, only called by other p2m code
  */
 
-struct page_info *p2m_alloc_ptp(struct p2m_domain *p2m, unsigned long type);
+mfn_t p2m_alloc_ptp(struct p2m_domain *p2m, unsigned long type);
 void p2m_free_ptp(struct p2m_domain *p2m, struct page_info *pg);
 
 /* Directly set a p2m entry: only for use by p2m code. Does not need