[Xen-devel] [PATCH MM-PART3 v3 4/9] xen/arm: mm: Rework xen_pt_update_entry to avoid use xenmap_operation

[Julien Grall <julien.grall@xxxxxxx>]

With the newly introduced flags, it is now possible to know how the page
will be updated through the flags.

All the use of xenmap_operation are now replaced with the flags. At the
same time, validity check are now removed as they are gathered in
xen_pt_check_entry().

Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
Reviewed-by: Andrii Anisov <andrii_anisov@xxxxxxxx>
Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>

---
    Changes in v3:
        - Add Stefano's reviewed-by

    Changes in v2:
        - Fix typo in the commit message
        - Add Andrii's reviewed-by
---
 xen/arch/arm/mm.c | 47 +++++++++++++++++++++++------------------------
 1 file changed, 23 insertions(+), 24 deletions(-)

diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index dcf041578b..b2b8bd3dc6 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -1047,34 +1047,33 @@ static int xen_pt_update_entry(enum xenmap_operation 
op, unsigned long addr,
     if ( !xen_pt_check_entry(*entry, mfn, flags) )
         return -EINVAL;
 
-    switch ( op ) {
-        case INSERT:
-        case RESERVE:
-            if ( op == RESERVE )
-                break;
+    /* If we are only populating page-table, then we are done. */
+    if ( flags & _PAGE_POPULATE )
+        return 0;
+
+    /* We are removing the page */
+    if ( !(flags & _PAGE_PRESENT) )
+        memset(&pte, 0x00, sizeof(pte));
+    else
+    {
+        /* We are inserting a mapping => Create new pte. */
+        if ( !mfn_eq(mfn, INVALID_MFN) )
+        {
             pte = mfn_to_xen_entry(mfn, PAGE_AI_MASK(flags));
-            pte.pt.ro = PAGE_RO_MASK(flags);
-            pte.pt.xn = PAGE_XN_MASK(flags);
-            BUG_ON(!pte.pt.ro && !pte.pt.xn);
+
+            /* Third level entries set pte.pt.table = 1 */
             pte.pt.table = 1;
-            write_pte(entry, pte);
-            break;
-        case MODIFY:
-        case REMOVE:
-            if ( op == REMOVE )
-                pte.bits = 0;
-            else
-            {
-                pte = *entry;
-                pte.pt.ro = PAGE_RO_MASK(flags);
-                pte.pt.xn = PAGE_XN_MASK(flags);
-            }
-            write_pte(entry, pte);
-            break;
-        default:
-            BUG();
+        }
+        else /* We are updating the permission => Copy the current pte. */
+            pte = *entry;
+
+        /* Set permission */
+        pte.pt.ro = PAGE_RO_MASK(flags);
+        pte.pt.xn = PAGE_XN_MASK(flags);
     }
 
+    write_pte(entry, pte);
+
     return 0;
 }
 
-- 
2.11.0


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