x86/mm: switch to new APIs in arch_init_memory

The function will map and unmap pages on demand.

Since we now map and unmap Xen PTE pages, we would like to track the
lifetime of mappings so that 1) we do not dereference memory through a
variable after it is unmapped, 2) we do not unmap more than once.
Therefore, we introduce the UNMAP_DOMAIN_PAGE macro to nullify the
variable after unmapping, and ignore NULL.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: Hongyan Xia <hongyxia@amazon.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 70b87c483092943f0c8d10dbaef6cf377f36a2f4..62507ca651590fc0fba4dff5dbe5b9e94542d80c 100644 (file)
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -356,19 +356,21 @@ void __init arch_init_memory(void)
             ASSERT(root_pgt_pv_xen_slots < ROOT_PAGETABLE_PV_XEN_SLOTS);
             if ( l4_table_offset(split_va) == l4_table_offset(split_va - 1) )
             {
-                l3_pgentry_t *l3tab = alloc_xen_pagetable();
+                mfn_t l3mfn = alloc_xen_pagetable_new();
 
-                if ( l3tab )
+                if ( !mfn_eq(l3mfn, INVALID_MFN) )
                 {
-                    const l3_pgentry_t *l3idle =
-                        l4e_to_l3e(idle_pg_table[l4_table_offset(split_va)]);
+                    const l3_pgentry_t *l3idle = map_l3t_from_l4e(
+                            idle_pg_table[l4_table_offset(split_va)]);
+                    l3_pgentry_t *l3tab = map_domain_page(l3mfn);
 
                     for ( i = 0; i < l3_table_offset(split_va); ++i )
                         l3tab[i] = l3idle[i];
                     for ( ; i < L3_PAGETABLE_ENTRIES; ++i )
                         l3tab[i] = l3e_empty();
-                    split_l4e = l4e_from_mfn(virt_to_mfn(l3tab),
-                                             __PAGE_HYPERVISOR_RW);
+                    split_l4e = l4e_from_mfn(l3mfn, __PAGE_HYPERVISOR_RW);
+                    UNMAP_DOMAIN_PAGE(l3idle);
+                    UNMAP_DOMAIN_PAGE(l3tab);
                 }
                 else
                     ++root_pgt_pv_xen_slots;

diff --git a/xen/include/xen/domain_page.h b/xen/include/xen/domain_page.h
index 32669a33399df0c9d3a045c74997f47cc67d7035..ab2be7b7191c5cded20739631cb37d3c6c3f9911 100644 (file)
--- a/xen/include/xen/domain_page.h
+++ b/xen/include/xen/domain_page.h
@@ -72,4 +72,12 @@ 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;                 \
+    }                               \
+} while ( false )
+
 #endif /* __XEN_DOMAIN_PAGE_H__ */