[Xen-changelog] [xen master] xen: arm: correctly handle removing a subset of a superpage mapping.

[patchbot@xxxxxxx]

commit 675498f8ca744f21a6f48d4d2d0ac4bc8db3bb89
Author:     Ian Campbell <ian.campbell@xxxxxxxxxx>
AuthorDate: Mon Jul 14 17:27:05 2014 +0100
Commit:     Ian Campbell <ian.campbell@xxxxxxxxxx>
CommitDate: Fri Jul 18 13:38:09 2014 +0100

    xen: arm: correctly handle removing a subset of a superpage mapping.
    
    This can be exercised for example via ballooning which will remove 4K
    regions from anywhere in the address space.
    
    Reported-by: Julien Grall <julien.grall@xxxxxxxxxx>
    Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
    Acked-by: Julien Grall <julien.grall@xxxxxxxxxx>
---
 xen/arch/arm/p2m.c |   29 +++++++++++++++++++++++++++--
 1 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index c3d63f0..2f855b5 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -604,8 +604,33 @@ static int apply_one_level(struct domain *d,
             return P2M_ONE_PROGRESS_NOP;
         }
 
-        if ( level < 3 && p2m_table(orig_pte) )
-            return P2M_ONE_DESCEND;
+        if ( level < 3 )
+        {
+            if ( p2m_table(orig_pte) )
+                return P2M_ONE_DESCEND;
+
+            if ( op == REMOVE &&
+                 !is_mapping_aligned(*addr, end_gpaddr,
+                                     0, /* maddr doesn't matter for remove */
+                                     level_size) )
+            {
+                /*
+                 * Removing a mapping from the middle of a superpage. Shatter
+                 * and descend.
+                 */
+                *flush = true;
+                rc = p2m_create_table(d, entry,
+                                      level_shift - PAGE_SHIFT, flush_cache);
+                if ( rc < 0 )
+                    return rc;
+
+                p2m->stats.shattered[level]++;
+                p2m->stats.mappings[level]--;
+                p2m->stats.mappings[level+1] += LPAE_ENTRIES;
+
+                return P2M_ONE_DESCEND;
+            }
+        }
 
         *flush = true;
 
--
generated by git-patchbot for /home/xen/git/xen.git#master

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