[Xen-devel] [PATCH v5 5/7] x86/mm: map_pages_to_xen would better have one exit path

[Hongyan Xia <hongyxia@amazon.com>]

From: Wei Liu <wei.liu2@citrix.com>

We will soon rewrite the function to handle dynamically mapping and
unmapping of page tables.

No functional change.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: Hongyan Xia <hongyxia@amazon.com>

---
Changed since v4:
- drop the end_of_loop goto label since this function may be refactored
  in the future and there are options to do things without the goto.

Changed since v3:
- remove asserts on rc since rc never gets changed to anything else.
- reword commit message.
---
 xen/arch/x86/mm.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 7160ddcb67..71e9c4b19e 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -5164,9 +5164,11 @@ int map_pages_to_xen(
     unsigned int flags)
 {
     bool locking = system_state > SYS_STATE_boot;
+    l3_pgentry_t *pl3e, ol3e;
     l2_pgentry_t *pl2e, ol2e;
     l1_pgentry_t *pl1e, ol1e;
     unsigned int  i;
+    int rc = -ENOMEM;
 
 #define flush_flags(oldf) do {                 \
     unsigned int o_ = (oldf);                  \
@@ -5184,10 +5186,11 @@ int map_pages_to_xen(
 
     while ( nr_mfns != 0 )
     {
-        l3_pgentry_t ol3e, *pl3e = virt_to_xen_l3e(virt);
+        pl3e = virt_to_xen_l3e(virt);
 
         if ( !pl3e )
-            return -ENOMEM;
+            goto out;
+
         ol3e = *pl3e;
 
         if ( cpu_has_page1gb &&
@@ -5277,7 +5280,7 @@ int map_pages_to_xen(
 
             l2t = alloc_xen_pagetable();
             if ( l2t == NULL )
-                return -ENOMEM;
+                goto out;
 
             for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++ )
                 l2e_write(l2t + i,
@@ -5306,7 +5309,7 @@ int map_pages_to_xen(
 
         pl2e = virt_to_xen_l2e(virt);
         if ( !pl2e )
-            return -ENOMEM;
+            goto out;
 
         if ( ((((virt >> PAGE_SHIFT) | mfn_x(mfn)) &
                ((1u << PAGETABLE_ORDER) - 1)) == 0) &&
@@ -5350,7 +5353,7 @@ int map_pages_to_xen(
             {
                 pl1e = virt_to_xen_l1e(virt);
                 if ( pl1e == NULL )
-                    return -ENOMEM;
+                    goto out;
             }
             else if ( l2e_get_flags(*pl2e) & _PAGE_PSE )
             {
@@ -5378,7 +5381,7 @@ int map_pages_to_xen(
 
                 l1t = alloc_xen_pagetable();
                 if ( l1t == NULL )
-                    return -ENOMEM;
+                    goto out;
 
                 for ( i = 0; i < L1_PAGETABLE_ENTRIES; i++ )
                     l1e_write(&l1t[i],
@@ -5524,7 +5527,10 @@ int map_pages_to_xen(
 
 #undef flush_flags
 
-    return 0;
+    rc = 0;
+
+ out:
+    return rc;
 }
 
 int populate_pt_range(unsigned long virt, unsigned long nr_mfns)
-- 
2.15.3.AMZN


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