[PATCH v4 2/4] x86_64/mm: map and unmap page tables in m2p_mapped

[Hongyan Xia <hx242@xxxxxxx>]

From: Wei Liu <wei.liu2@xxxxxxxxxx>

Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
Signed-off-by: Hongyan Xia <hongyxia@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

---
Changed in v3:
- rename l3e_ro_mpt and l2e_ro_mpt, just call them l3e and l2e.

Changed in v2:
- avoid adding goto labels, simply get the PTE and unmap quickly.
- code style fixes.
---
 xen/arch/x86/x86_64/mm.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/xen/arch/x86/x86_64/mm.c b/xen/arch/x86/x86_64/mm.c
index cee836ec37..41755ded26 100644
--- a/xen/arch/x86/x86_64/mm.c
+++ b/xen/arch/x86/x86_64/mm.c
@@ -129,14 +129,13 @@ static mfn_t alloc_hotadd_mfn(struct mem_hotadd_info 
*info)
 static int m2p_mapped(unsigned long spfn)
 {
     unsigned long va;
-    l3_pgentry_t *l3_ro_mpt;
-    l2_pgentry_t *l2_ro_mpt;
+    l3_pgentry_t l3e;
+    l2_pgentry_t l2e;
 
     va = RO_MPT_VIRT_START + spfn * sizeof(*machine_to_phys_mapping);
-    l3_ro_mpt = l4e_to_l3e(idle_pg_table[l4_table_offset(va)]);
+    l3e = l3e_from_l4e(idle_pg_table[l4_table_offset(va)], 
l3_table_offset(va));
 
-    switch ( l3e_get_flags(l3_ro_mpt[l3_table_offset(va)]) &
-             (_PAGE_PRESENT |_PAGE_PSE))
+    switch ( l3e_get_flags(l3e) & (_PAGE_PRESENT | _PAGE_PSE) )
     {
         case _PAGE_PSE|_PAGE_PRESENT:
             return M2P_1G_MAPPED;
@@ -146,9 +145,9 @@ static int m2p_mapped(unsigned long spfn)
         default:
             return M2P_NO_MAPPED;
     }
-    l2_ro_mpt = l3e_to_l2e(l3_ro_mpt[l3_table_offset(va)]);
+    l2e = l2e_from_l3e(l3e, l2_table_offset(va));
 
-    if (l2e_get_flags(l2_ro_mpt[l2_table_offset(va)]) & _PAGE_PRESENT)
+    if ( l2e_get_flags(l2e) & _PAGE_PRESENT )
         return M2P_2M_MAPPED;
 
     return M2P_NO_MAPPED;
-- 
2.24.1.AMZN