[v3,7/9] x86/mm: make sure there is one exit path for modify_xen_mappings

Commit Message

Xia, Hongyan Oct. 2, 2019, 5:16 p.m. UTC

From: Wei Liu <[e-mail]>

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

No functional change.

Signed-off-by: Wei Liu <[e-mail]>
---
 xen/arch/x86/mm.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

Comments

Jan Beulich Nov. 20, 2019, 4:26 p.m. UTC | #1

On 02.10.2019 19:16, Hongyan Xia wrote:
> @@ -5468,7 +5469,11 @@ 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;
> +            {
> +                ASSERT(rc == -ENOMEM);
> +                goto out;
> +            }

Same as for patch 5 - I think these ASSERT()s aren't very helpful.

Jan

Patch

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 5a5f0685cc..3838343b87 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -5425,6 +5425,7 @@  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)
@@ -5468,7 +5469,11 @@  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;
+            {
+                ASSERT(rc == -ENOMEM);
+                goto out;
+            }
+
             for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++ )
                 l2e_write(l2t + i,
                           l2e_from_pfn(l3e_get_pfn(*pl3e) +
@@ -5525,7 +5530,11 @@  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;
+                {
+                    ASSERT(rc == -ENOMEM);
+                    goto out;
+                }
+
                 for ( i = 0; i < L1_PAGETABLE_ENTRIES; i++ )
                     l1e_write(&l1t[i],
                               l1e_from_pfn(l2e_get_pfn(*pl2e) + i,
@@ -5658,7 +5667,10 @@  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