[Xen-changelog] [xen staging] x86/mm: switch to new APIs in arch_init_memory

[patchbot@xxxxxxx]

commit 109ecb894525e16cf84f34ead15467980fa2edfd
Author:     Wei Liu <wei.liu2@xxxxxxxxxx>
AuthorDate: Thu Mar 5 10:42:18 2020 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Mar 5 10:42:18 2020 +0100

    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@xxxxxxxxxx>
    Signed-off-by: Hongyan Xia <hongyxia@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/mm.c             | 14 ++++++++------
 xen/include/xen/domain_page.h |  8 ++++++++
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 70b87c4830..62507ca651 100644
--- 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 32669a3339..ab2be7b719 100644
--- 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__ */
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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