[Xen-devel] [for-4.11][PATCH v7 01/16] x86/mm: skip incrementing mfn if it is not a valid mfn

[Julien Grall <julien.grall@xxxxxxx>]

From: Wei Liu <wei.liu2@xxxxxxxxxx>

In a follow-up patch, some callers will be switched to pass
INVALID_MFN instead of zero for non-present mappings. So skip
incrementing mfn if it is not a valid one.

Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
[Rework the commit message]
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

--

Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

    Changes in v7:
        - Add Jan's reviewed-by
        - Fix typo in the commit message

    Changes in v6:
        - Update commit message

    Changes in v5:
        - Patch added
---
 xen/arch/x86/mm.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 17558e0c8c..3aed94bda5 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -4725,7 +4725,8 @@ int map_pages_to_xen(
             }
 
             virt    += 1UL << L3_PAGETABLE_SHIFT;
-            mfn     += 1UL << (L3_PAGETABLE_SHIFT - PAGE_SHIFT);
+            if ( !mfn_eq(_mfn(mfn), INVALID_MFN) )
+                mfn += 1UL << (L3_PAGETABLE_SHIFT - PAGE_SHIFT);
             nr_mfns -= 1UL << (L3_PAGETABLE_SHIFT - PAGE_SHIFT);
             continue;
         }
@@ -4750,7 +4751,8 @@ int map_pages_to_xen(
                 if ( i > nr_mfns )
                     i = nr_mfns;
                 virt    += i << PAGE_SHIFT;
-                mfn     += i;
+                if ( !mfn_eq(_mfn(mfn), INVALID_MFN) )
+                    mfn += i;
                 nr_mfns -= i;
                 continue;
             }
@@ -4818,7 +4820,8 @@ int map_pages_to_xen(
             }
 
             virt    += 1UL << L2_PAGETABLE_SHIFT;
-            mfn     += 1UL << PAGETABLE_ORDER;
+            if ( !mfn_eq(_mfn(mfn), INVALID_MFN) )
+                mfn += 1UL << PAGETABLE_ORDER;
             nr_mfns -= 1UL << PAGETABLE_ORDER;
         }
         else
@@ -4847,7 +4850,8 @@ int map_pages_to_xen(
                     if ( i > nr_mfns )
                         i = nr_mfns;
                     virt    += i << L1_PAGETABLE_SHIFT;
-                    mfn     += i;
+                    if ( !mfn_eq(_mfn(mfn), INVALID_MFN) )
+                        mfn += i;
                     nr_mfns -= i;
                     goto check_l3;
                 }
@@ -4892,7 +4896,8 @@ int map_pages_to_xen(
             }
 
             virt    += 1UL << L1_PAGETABLE_SHIFT;
-            mfn     += 1UL;
+            if ( !mfn_eq(_mfn(mfn), INVALID_MFN) )
+                mfn += 1UL;
             nr_mfns -= 1UL;
 
             if ( (flags == PAGE_HYPERVISOR) &&
-- 
2.11.0


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