[Xen-devel] [PATCH v3 12/15] xen/arm: Shatter large pages when using mem_acces

[Tamas K Lengyel <tklengyel@xxxxxxxxxxxxx>]

When using mem_acccess+mem_event, the coarsest granularity is required
in the pagetables, therefore we shatter each large page (1GB/2MB) as we
apply the permission changes.

Signed-off-by: Tamas K Lengyel <tklengyel@xxxxxxxxxxxxx>
---
 xen/arch/arm/p2m.c | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index e8f5671..0d447e2 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -1132,12 +1132,30 @@ static bool_t p2m_set_entry(struct domain *d, paddr_t 
paddr, p2m_access_t p2ma)
 
     pte = &first[first_table_offset(paddr)];
     if ( !p2m_table(*pte) )
-        goto done;
+    {
+        /* This is a mapping of a 1GB page, shatter it */
+        rc = p2m_create_table(d, pte, FIRST_SHIFT - PAGE_SHIFT, 1);
+        if ( rc < 0 )
+            goto err;
+
+        p2m->stats.shattered[1]++;
+        p2m->stats.mappings[1]--;
+        p2m->stats.mappings[2] += LPAE_ENTRIES;
+    }
 
     second = map_domain_page(pte->p2m.base);
     pte = &second[second_table_offset(paddr)];
     if ( !p2m_table(*pte) )
-        goto done;
+    {
+        /* This is a mapping of 2MB page, shatter it */
+        rc = p2m_create_table(d, pte, SECOND_SHIFT - PAGE_SHIFT, 1);
+        if ( rc < 0 )
+            goto err;
+
+        p2m->stats.shattered[2]++;
+        p2m->stats.mappings[2]--;
+        p2m->stats.mappings[3] += LPAE_ENTRIES;
+    }
 
     third = map_domain_page(pte->p2m.base);
     pte = &third[third_table_offset(paddr)];
@@ -1148,7 +1166,6 @@ static bool_t p2m_set_entry(struct domain *d, paddr_t 
paddr, p2m_access_t p2ma)
     if ( !p2m_table(*pte) )
         pte->bits = 0;
 
-done:
     if ( p2m_valid(*pte) )
     {
         ASSERT(pte->p2m.type != p2m_invalid);
@@ -1159,11 +1176,11 @@ done:
         rc = 1;
     }
 
+err:
     if (third) unmap_domain_page(third);
     if (second) unmap_domain_page(second);
     if (first) unmap_domain_page(first);
 
-err:
     return rc;
 }
 
-- 
2.1.0.rc1


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