[Xen-devel] [PATCH v5 6/7] x86/mm: make sure there is one exit path for modify_xen_mappings

[Hongyan Xia <hongyxia@xxxxxxxxxx>]

From: Wei Liu <wei.liu2@xxxxxxxxxx>

We will soon need to handle dynamically mapping / unmapping page
tables in the said function.

No functional change.

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

---
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 it never gets changed to anything else.
---
 xen/arch/x86/mm.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 71e9c4b19e..6b589762b1 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -5557,6 +5557,7 @@ int modify_xen_mappings(unsigned long s, unsigned long e, 
unsigned int nf)
     l1_pgentry_t *pl1e;
     unsigned int  i;
     unsigned long v = s;
+    int rc = -ENOMEM;
 
     /* Set of valid PTE bits which may be altered. */
 #define FLAGS_MASK (_PAGE_NX|_PAGE_RW|_PAGE_PRESENT)
@@ -5600,7 +5601,8 @@ int modify_xen_mappings(unsigned long s, unsigned long e, 
unsigned int nf)
             /* PAGE1GB: shatter the superpage and fall through. */
             l2t = alloc_xen_pagetable();
             if ( !l2t )
-                return -ENOMEM;
+                goto out;
+
             for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++ )
                 l2e_write(l2t + i,
                           l2e_from_pfn(l3e_get_pfn(*pl3e) +
@@ -5657,7 +5659,8 @@ int modify_xen_mappings(unsigned long s, unsigned long e, 
unsigned int nf)
                 /* PSE: shatter the superpage and try again. */
                 l1t = alloc_xen_pagetable();
                 if ( !l1t )
-                    return -ENOMEM;
+                    goto out;
+
                 for ( i = 0; i < L1_PAGETABLE_ENTRIES; i++ )
                     l1e_write(&l1t[i],
                               l1e_from_pfn(l2e_get_pfn(*pl2e) + i,
@@ -5790,7 +5793,10 @@ int modify_xen_mappings(unsigned long s, unsigned long 
e, unsigned int nf)
     flush_area(NULL, FLUSH_TLB_GLOBAL);
 
 #undef FLAGS_MASK
-    return 0;
+    rc = 0;
+
+ out:
+    return rc;
 }
 
 #undef flush_area
-- 
2.15.3.AMZN


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