p2m: change write_p2m_entry to return an error code

This is in preparation for also changing p2m_entry_modify to return an
error code.

No functional change intended.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: George Dunlap <george.dunlap@citrix.com>

xen/arch/x86/mm/hap/hap.c

@@ -708,7 +708,7 @@ static void hap_update_paging_modes(struct vcpu *v)
     put_gfn(d, cr3_gfn);
 }
 
-static void
+static int
 hap_write_p2m_entry(struct p2m_domain *p2m, unsigned long gfn, l1_pgentry_t *p,
                     l1_pgentry_t new, unsigned int level)
 {
@@ -746,6 +746,8 @@ hap_write_p2m_entry(struct p2m_domain *p2m, unsigned long gfn, l1_pgentry_t *p,
 
     if ( flush_nestedp2m )
         p2m_flush_nestedp2m(d);
+
+    return 0;
 }
 
 static unsigned long hap_gva_to_gfn_real_mode(

xen/arch/x86/mm/hap/nested_hap.c

@@ -71,7 +71,7 @@
 /*        NESTED VIRT P2M FUNCTIONS         */
 /********************************************/
 
-void
+int
 nestedp2m_write_p2m_entry(struct p2m_domain *p2m, unsigned long gfn,
     l1_pgentry_t *p, l1_pgentry_t new, unsigned int level)
 {
@@ -87,6 +87,8 @@ nestedp2m_write_p2m_entry(struct p2m_domain *p2m, unsigned long gfn,
         flush_tlb_mask(p2m->dirty_cpumask);
 
     paging_unlock(d);
+
+    return 0;
 }
 
 /********************************************/

xen/arch/x86/mm/p2m-pt.c

@@ -184,6 +184,8 @@ p2m_next_level(struct p2m_domain *p2m, void **table,
     l1_pgentry_t *p2m_entry, new_entry;
     void *next;
     unsigned int flags;
+    int rc;
+    mfn_t mfn;
 
     if ( !(p2m_entry = p2m_find_entry(*table, gfn_remainder, gfn,
                                       shift, max)) )
@@ -194,7 +196,7 @@ p2m_next_level(struct p2m_domain *p2m, void **table,
     /* PoD/paging: Not present doesn't imply empty. */
     if ( !flags )
     {
-        mfn_t mfn = p2m_alloc_ptp(p2m, level);
+        mfn = p2m_alloc_ptp(p2m, level);
 
         if ( mfn_eq(mfn, INVALID_MFN) )
             return -ENOMEM;
@@ -202,13 +204,14 @@ p2m_next_level(struct p2m_domain *p2m, void **table,
         new_entry = l1e_from_mfn(mfn, P2M_BASE_FLAGS | _PAGE_RW);
 
         p2m_add_iommu_flags(&new_entry, level, IOMMUF_readable|IOMMUF_writable);
-        p2m->write_p2m_entry(p2m, gfn, p2m_entry, new_entry, level + 1);
+        rc = p2m->write_p2m_entry(p2m, gfn, p2m_entry, new_entry, level + 1);
+        if ( rc )
+            goto error;
     }
     else if ( flags & _PAGE_PSE )
     {
         /* Split superpages pages into smaller ones. */
         unsigned long pfn = l1e_get_pfn(*p2m_entry);
-        mfn_t mfn;
         l1_pgentry_t *l1_entry;
         unsigned int i;
 
@@ -250,14 +253,23 @@ p2m_next_level(struct p2m_domain *p2m, void **table,
         {
             new_entry = l1e_from_pfn(pfn | (i << ((level - 1) * PAGETABLE_ORDER)),
                                      flags);
-            p2m->write_p2m_entry(p2m, gfn, l1_entry + i, new_entry, level);
+            rc = p2m->write_p2m_entry(p2m, gfn, l1_entry + i, new_entry, level);
+            if ( rc )
+            {
+                unmap_domain_page(l1_entry);
+                goto error;
+            }
         }
 
         unmap_domain_page(l1_entry);
 
         new_entry = l1e_from_mfn(mfn, P2M_BASE_FLAGS | _PAGE_RW);
-        p2m_add_iommu_flags(&new_entry, level, IOMMUF_readable|IOMMUF_writable);
-        p2m->write_p2m_entry(p2m, gfn, p2m_entry, new_entry, level + 1);
+        p2m_add_iommu_flags(&new_entry, level,
+                            IOMMUF_readable|IOMMUF_writable);
+        rc = p2m->write_p2m_entry(p2m, gfn, p2m_entry, new_entry,
+                                  level + 1);
+        if ( rc )
+            goto error;
     }
     else
         ASSERT(flags & _PAGE_PRESENT);
@@ -268,6 +280,12 @@ p2m_next_level(struct p2m_domain *p2m, void **table,
     *table = next;
 
     return 0;
+
+ error:
+    ASSERT(rc && mfn_valid(mfn));
+    ASSERT_UNREACHABLE();
+    p2m_free_ptp(p2m, mfn_to_page(mfn));
+    return rc;
 }
 
 /*
@@ -321,7 +339,12 @@ static int p2m_pt_set_recalc_range(struct p2m_domain *p2m,
             if ( (l1e_get_flags(e) & _PAGE_PRESENT) && !needs_recalc(l1, e) )
             {
                 set_recalc(l1, e);
-                p2m->write_p2m_entry(p2m, first_gfn, pent, e, level);
+                err = p2m->write_p2m_entry(p2m, first_gfn, pent, e, level);
+                if ( err )
+                {
+                    ASSERT_UNREACHABLE();
+                    goto out;
+                }
             }
             first_gfn += 1UL << (i * PAGETABLE_ORDER);
         }
@@ -392,14 +415,24 @@ static int do_recalc(struct p2m_domain *p2m, unsigned long gfn)
                      !needs_recalc(l1, ent) )
                 {
                     set_recalc(l1, ent);
-                    p2m->write_p2m_entry(p2m, gfn - remainder, &ptab[i],
-                                         ent, level);
+                    err = p2m->write_p2m_entry(p2m, gfn - remainder, &ptab[i],
+                                               ent, level);
+                    if ( err )
+                    {
+                        ASSERT_UNREACHABLE();
+                        goto out;
+                    }
                 }
                 remainder -= 1UL << ((level - 1) * PAGETABLE_ORDER);
             }
             smp_wmb();
             clear_recalc(l1, e);
-            p2m->write_p2m_entry(p2m, gfn, pent, e, level + 1);
+            err = p2m->write_p2m_entry(p2m, gfn, pent, e, level + 1);
+            if ( err )
+            {
+                ASSERT_UNREACHABLE();
+                goto out;
+            }
         }
         unmap_domain_page((void *)((unsigned long)pent & PAGE_MASK));
     }
@@ -444,7 +477,8 @@ static int do_recalc(struct p2m_domain *p2m, unsigned long gfn)
         }
         else
             clear_recalc(l1, e);
-        p2m->write_p2m_entry(p2m, gfn, pent, e, level + 1);
+        err = p2m->write_p2m_entry(p2m, gfn, pent, e, level + 1);
+        ASSERT(!err);
     }
 
  out:
@@ -595,8 +629,10 @@ p2m_pt_set_entry(struct p2m_domain *p2m, gfn_t gfn_, mfn_t mfn,
         if ( entry_content.l1 != 0 )
             p2m_add_iommu_flags(&entry_content, 0, iommu_pte_flags);
 
-        p2m->write_p2m_entry(p2m, gfn, p2m_entry, entry_content, 3);
+        rc = p2m->write_p2m_entry(p2m, gfn, p2m_entry, entry_content, 3);
         /* NB: paging_write_p2m_entry() handles tlb flushes properly */
+        if ( rc )
+            goto out;
     }
     else 
     {
@@ -633,8 +669,10 @@ p2m_pt_set_entry(struct p2m_domain *p2m, gfn_t gfn_, mfn_t mfn,
             p2m_add_iommu_flags(&entry_content, 0, iommu_pte_flags);
 
         /* level 1 entry */
-        p2m->write_p2m_entry(p2m, gfn, p2m_entry, entry_content, 1);
+        rc = p2m->write_p2m_entry(p2m, gfn, p2m_entry, entry_content, 1);
         /* NB: paging_write_p2m_entry() handles tlb flushes properly */
+        if ( rc )
+            goto out;
     }
     else if ( page_order == PAGE_ORDER_2M )
     {
@@ -669,8 +707,10 @@ p2m_pt_set_entry(struct p2m_domain *p2m, gfn_t gfn_, mfn_t mfn,
         if ( entry_content.l1 != 0 )
             p2m_add_iommu_flags(&entry_content, 0, iommu_pte_flags);
 
-        p2m->write_p2m_entry(p2m, gfn, p2m_entry, entry_content, 2);
+        rc = p2m->write_p2m_entry(p2m, gfn, p2m_entry, entry_content, 2);
         /* NB: paging_write_p2m_entry() handles tlb flushes properly */
+        if ( rc )
+            goto out;
     }
 
     /* Track the highest gfn for which we have ever had a valid mapping */
@@ -894,8 +934,15 @@ static void p2m_pt_change_entry_type_global(struct p2m_domain *p2m,
         if ( (l1e_get_flags(e) & _PAGE_PRESENT) &&
              !needs_recalc(l1, e) )
         {
+            int rc;
+
             set_recalc(l1, e);
-            p2m->write_p2m_entry(p2m, gfn, &tab[i], e, 4);
+            rc = p2m->write_p2m_entry(p2m, gfn, &tab[i], e, 4);
+            if ( rc )
+            {
+                ASSERT_UNREACHABLE();
+                break;
+            }
             ++changed;
         }
         gfn += 1UL << (L4_PAGETABLE_SHIFT - PAGE_SHIFT);

xen/arch/x86/mm/paging.c

@@ -932,18 +932,22 @@ void paging_update_nestedmode(struct vcpu *v)
 }
 #endif
 
-void paging_write_p2m_entry(struct p2m_domain *p2m, unsigned long gfn,
-                            l1_pgentry_t *p, l1_pgentry_t new,
-                            unsigned int level)
+int paging_write_p2m_entry(struct p2m_domain *p2m, unsigned long gfn,
+                           l1_pgentry_t *p, l1_pgentry_t new,
+                           unsigned int level)
 {
     struct domain *d = p2m->domain;
     struct vcpu *v = current;
+    int rc = 0;
+
     if ( v->domain != d )
         v = d->vcpu ? d->vcpu[0] : NULL;
     if ( likely(v && paging_mode_enabled(d) && paging_get_hostmode(v) != NULL) )
-        paging_get_hostmode(v)->write_p2m_entry(p2m, gfn, p, new, level);
+        rc = paging_get_hostmode(v)->write_p2m_entry(p2m, gfn, p, new, level);
     else
         safe_write_pte(p, new);
+
+    return rc;
 }
 
 int paging_set_allocation(struct domain *d, unsigned int pages, bool *preempted)

xen/arch/x86/mm/shadow/common.c

@@ -3176,7 +3176,7 @@ static void sh_unshadow_for_p2m_change(struct domain *d, unsigned long gfn,
     }
 }
 
-void
+int
 shadow_write_p2m_entry(struct p2m_domain *p2m, unsigned long gfn,
                        l1_pgentry_t *p, l1_pgentry_t new,
                        unsigned int level)
@@ -3211,6 +3211,8 @@ shadow_write_p2m_entry(struct p2m_domain *p2m, unsigned long gfn,
 #endif
 
     paging_unlock(d);
+
+    return 0;
 }
 
 /**************************************************************************/

xen/arch/x86/mm/shadow/none.c

@@ -60,11 +60,12 @@ static void _update_paging_modes(struct vcpu *v)
     ASSERT_UNREACHABLE();
 }
 
-static void _write_p2m_entry(struct p2m_domain *p2m, unsigned long gfn,
-                             l1_pgentry_t *p, l1_pgentry_t new,
-                             unsigned int level)
+static int _write_p2m_entry(struct p2m_domain *p2m, unsigned long gfn,
+                            l1_pgentry_t *p, l1_pgentry_t new,
+                            unsigned int level)
 {
     ASSERT_UNREACHABLE();
+    return -EOPNOTSUPP;
 }
 
 static const struct paging_mode sh_paging_none = {

xen/arch/x86/mm/shadow/private.h

@@ -372,9 +372,9 @@ extern int sh_remove_write_access(struct domain *d, mfn_t readonly_mfn,
                                   unsigned long fault_addr);
 
 /* Functions that atomically write PT/P2M entries and update state */
-void shadow_write_p2m_entry(struct p2m_domain *p2m, unsigned long gfn,
-                            l1_pgentry_t *p, l1_pgentry_t new,
-                            unsigned int level);
+int shadow_write_p2m_entry(struct p2m_domain *p2m, unsigned long gfn,
+                           l1_pgentry_t *p, l1_pgentry_t new,
+                           unsigned int level);
 
 /* Update all the things that are derived from the guest's CR0/CR3/CR4.
  * Called to initialize paging structures if the paging mode

xen/include/asm-x86/p2m.h

@@ -265,7 +265,7 @@ struct p2m_domain {
                                                   unsigned long last_gfn);
     void               (*memory_type_changed)(struct p2m_domain *p2m);
     
-    void               (*write_p2m_entry)(struct p2m_domain *p2m,
+    int                (*write_p2m_entry)(struct p2m_domain *p2m,
                                           unsigned long gfn, l1_pgentry_t *p,
                                           l1_pgentry_t new, unsigned int level);
     long               (*audit_p2m)(struct p2m_domain *p2m);
@@ -837,7 +837,7 @@ void p2m_flush_nestedp2m(struct domain *d);
 /* Flushes the np2m specified by np2m_base (if it exists) */
 void np2m_flush_base(struct vcpu *v, unsigned long np2m_base);
 
-void nestedp2m_write_p2m_entry(struct p2m_domain *p2m, unsigned long gfn,
+int nestedp2m_write_p2m_entry(struct p2m_domain *p2m, unsigned long gfn,
     l1_pgentry_t *p, l1_pgentry_t new, unsigned int level);
 
 /*

xen/include/asm-x86/paging.h

@@ -124,7 +124,7 @@ struct paging_mode {
     void          (*update_cr3            )(struct vcpu *v, int do_locking,
                                             bool noflush);
     void          (*update_paging_modes   )(struct vcpu *v);
-    void          (*write_p2m_entry       )(struct p2m_domain *p2m,
+    int           (*write_p2m_entry       )(struct p2m_domain *p2m,
                                             unsigned long gfn,
                                             l1_pgentry_t *p, l1_pgentry_t new,
                                             unsigned int level);
@@ -340,9 +340,9 @@ static inline void safe_write_pte(l1_pgentry_t *p, l1_pgentry_t new)
  * we are writing. */
 struct p2m_domain;
 
-void paging_write_p2m_entry(struct p2m_domain *p2m, unsigned long gfn,
-                            l1_pgentry_t *p, l1_pgentry_t new,
-                            unsigned int level);
+int paging_write_p2m_entry(struct p2m_domain *p2m, unsigned long gfn,
+                           l1_pgentry_t *p, l1_pgentry_t new,
+                           unsigned int level);
 
 /*
  * Called from the guest to indicate that the a process is being