[Xen-changelog] [xen-unstable] x86, shadow: Allow removing writable mappings from splintered page tables.

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1221474882 -3600
# Node ID c353f07bae84133a83ec1dbf54bc5f868fd45bb2
# Parent  8f456fcd8af115672a2e7a310403fc4d9f125b75
x86, shadow: Allow removing writable mappings from splintered page tables.

The moving of the pagetable mapping in the linux kernel exposed the
fact that under the linux kernel sh_rm_write_access_from_sl1p was
always failing.

Linux seems to use big pages to access page tables, so we should
instruct the shadow code to be able to remove writable mappings from
splintered pagetables as well, avoiding using OS heuristic (which were
failing in 2.6.27 before George patch, leading to brute-force search
at each resync).

Signed-off-by: Gianluca Guida <gianluca.guida@xxxxxxxxxxxxx>
---
 xen/arch/x86/mm/shadow/common.c |   11 +++++++----
 xen/arch/x86/mm/shadow/multi.c  |    3 ++-
 2 files changed, 9 insertions(+), 5 deletions(-)

diff -r 8f456fcd8af1 -r c353f07bae84 xen/arch/x86/mm/shadow/common.c
--- a/xen/arch/x86/mm/shadow/common.c   Sat Sep 13 08:15:26 2008 +0100
+++ b/xen/arch/x86/mm/shadow/common.c   Mon Sep 15 11:34:42 2008 +0100
@@ -2464,22 +2464,25 @@ int sh_remove_write_access_from_sl1p(str
     ASSERT(mfn_valid(smfn));
     ASSERT(mfn_valid(gmfn));
     
-    if ( sp->type == SH_type_l1_32_shadow )
+    if ( sp->type == SH_type_l1_32_shadow
+         || sp->type == SH_type_fl1_32_shadow )
     {
         return SHADOW_INTERNAL_NAME(sh_rm_write_access_from_sl1p,2)
             (v, gmfn, smfn, off);
     }
 #if CONFIG_PAGING_LEVELS >= 3
-    else if ( sp->type == SH_type_l1_pae_shadow )
+    else if ( sp->type == SH_type_l1_pae_shadow
+              || sp->type == SH_type_fl1_pae_shadow )
         return SHADOW_INTERNAL_NAME(sh_rm_write_access_from_sl1p,3)
             (v, gmfn, smfn, off);
 #if CONFIG_PAGING_LEVELS >= 4
-    else if ( sp->type == SH_type_l1_64_shadow )
+    else if ( sp->type == SH_type_l1_64_shadow
+              || sp->type == SH_type_fl1_64_shadow )
         return SHADOW_INTERNAL_NAME(sh_rm_write_access_from_sl1p,4)
             (v, gmfn, smfn, off);
 #endif
 #endif
-    
+
     return 0;
 }
 #endif 
diff -r 8f456fcd8af1 -r c353f07bae84 xen/arch/x86/mm/shadow/multi.c
--- a/xen/arch/x86/mm/shadow/multi.c    Sat Sep 13 08:15:26 2008 +0100
+++ b/xen/arch/x86/mm/shadow/multi.c    Mon Sep 15 11:34:42 2008 +0100
@@ -4539,7 +4539,8 @@ int sh_rm_write_access_from_sl1p(struct 
     sp = mfn_to_shadow_page(smfn);
 
     if ( sp->mbz != 0
-         || (sp->type != SH_type_l1_shadow) )
+         || (sp->type != SH_type_l1_shadow
+             && sp->type != SH_type_fl1_shadow) )
         goto fail;
 
     sl1p = sh_map_domain_page(smfn);

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