[Xen-devel] [PATCH 3/5] x86_64/mm: map and unmap page tables in share_hotadd_m2p_table

[Hongyan Xia <hx242@xxxxxxx>]

From: Wei Liu <wei.liu2@xxxxxxxxxx>

Fetch lYe by mapping and unmapping lXe instead of using the direct map,
which is now done via the new lYe_from_lXe() helpers.

Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
Signed-off-by: Hongyan Xia <hongyxia@xxxxxxxxxx>
---
 xen/arch/x86/x86_64/mm.c   | 12 ++++++------
 xen/include/asm-x86/page.h | 18 ++++++++++++++++++
 2 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/xen/arch/x86/x86_64/mm.c b/xen/arch/x86/x86_64/mm.c
index a440dac25e..2680173fab 100644
--- a/xen/arch/x86/x86_64/mm.c
+++ b/xen/arch/x86/x86_64/mm.c
@@ -173,14 +173,14 @@ static int share_hotadd_m2p_table(struct mem_hotadd_info 
*info)
           v += n << PAGE_SHIFT )
     {
         n = L2_PAGETABLE_ENTRIES * L1_PAGETABLE_ENTRIES;
-        l3e = l4e_to_l3e(idle_pg_table[l4_table_offset(v)])[
-            l3_table_offset(v)];
+        l3e = l3e_from_l4e(idle_pg_table[l4_table_offset(v)],
+                           l3_table_offset(v));
         if ( !(l3e_get_flags(l3e) & _PAGE_PRESENT) )
             continue;
         if ( !(l3e_get_flags(l3e) & _PAGE_PSE) )
         {
             n = L1_PAGETABLE_ENTRIES;
-            l2e = l3e_to_l2e(l3e)[l2_table_offset(v)];
+            l2e = l2e_from_l3e(l3e, l2_table_offset(v));
             if ( !(l2e_get_flags(l2e) & _PAGE_PRESENT) )
                 continue;
             m2p_start_mfn = l2e_get_mfn(l2e);
@@ -201,11 +201,11 @@ static int share_hotadd_m2p_table(struct mem_hotadd_info 
*info)
           v != RDWR_COMPAT_MPT_VIRT_END;
           v += 1 << L2_PAGETABLE_SHIFT )
     {
-        l3e = l4e_to_l3e(idle_pg_table[l4_table_offset(v)])[
-            l3_table_offset(v)];
+        l3e = l3e_from_l4e(idle_pg_table[l4_table_offset(v)],
+                           l3_table_offset(v));
         if ( !(l3e_get_flags(l3e) & _PAGE_PRESENT) )
             continue;
-        l2e = l3e_to_l2e(l3e)[l2_table_offset(v)];
+        l2e = l2e_from_l3e(l3e, l2_table_offset(v));
         if ( !(l2e_get_flags(l2e) & _PAGE_PRESENT) )
             continue;
         m2p_start_mfn = l2e_get_mfn(l2e);
diff --git a/xen/include/asm-x86/page.h b/xen/include/asm-x86/page.h
index c98d8f5ede..d4752a5925 100644
--- a/xen/include/asm-x86/page.h
+++ b/xen/include/asm-x86/page.h
@@ -196,6 +196,24 @@ static inline l4_pgentry_t l4e_from_paddr(paddr_t pa, 
unsigned int flags)
 #define map_l2t_from_l3e(x)        (l2_pgentry_t 
*)map_domain_page(l3e_get_mfn(x))
 #define map_l3t_from_l4e(x)        (l3_pgentry_t 
*)map_domain_page(l4e_get_mfn(x))
 
+#define l1e_from_l2e(l2e, off) ({                   \
+        l1_pgentry_t *l1t = map_l1t_from_l2e(l2e);  \
+        l1_pgentry_t l1e = l1t[off];                \
+        UNMAP_DOMAIN_PAGE(l1t);                     \
+        l1e; })
+
+#define l2e_from_l3e(l3e, off) ({                   \
+        l2_pgentry_t *l2t = map_l2t_from_l3e(l3e);  \
+        l2_pgentry_t l2e = l2t[off];                \
+        UNMAP_DOMAIN_PAGE(l2t);                     \
+        l2e; })
+
+#define l3e_from_l4e(l4e, off) ({                   \
+        l3_pgentry_t *l3t = map_l3t_from_l4e(l4e);  \
+        l3_pgentry_t l3e = l3t[off];                \
+        UNMAP_DOMAIN_PAGE(l3t);                     \
+        l3e; })
+
 /* Given a virtual address, get an entry offset into a page table. */
 #define l1_table_offset(a)         \
     (((a) >> L1_PAGETABLE_SHIFT) & (L1_PAGETABLE_ENTRIES - 1))
-- 
2.24.1.AMZN


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