summaryrefslogtreecommitdiffstats
path: root/arch/x86/mm/pageattr.c
diff options
context:
space:
mode:
authorDavid S. Miller <davem@davemloft.net>2010-04-03 15:49:14 -0700
committerDavid S. Miller <davem@davemloft.net>2010-04-03 15:49:14 -0700
commit87e8b821ed8db3dab03d96cd542e29666bf210aa (patch)
tree0027060473aafbbb125655ba027319c8a1a665fc /arch/x86/mm/pageattr.c
parent33cd9dfa3a13e3d8e41aef225a9f98169816723b (diff)
parent5e11611a5d22252f3f9c169a3c9377eac0c32033 (diff)
Merge branch 'master' of /home/davem/src/GIT/linux-2.6/
Diffstat (limited to 'arch/x86/mm/pageattr.c')
-rw-r--r--arch/x86/mm/pageattr.c25
1 files changed, 23 insertions, 2 deletions
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 1d4eb93d333..cf07c26d9a4 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -291,8 +291,29 @@ static inline pgprot_t static_protections(pgprot_t prot, unsigned long address,
*/
if (kernel_set_to_readonly &&
within(address, (unsigned long)_text,
- (unsigned long)__end_rodata_hpage_align))
- pgprot_val(forbidden) |= _PAGE_RW;
+ (unsigned long)__end_rodata_hpage_align)) {
+ unsigned int level;
+
+ /*
+ * Don't enforce the !RW mapping for the kernel text mapping,
+ * if the current mapping is already using small page mapping.
+ * No need to work hard to preserve large page mappings in this
+ * case.
+ *
+ * This also fixes the Linux Xen paravirt guest boot failure
+ * (because of unexpected read-only mappings for kernel identity
+ * mappings). In this paravirt guest case, the kernel text
+ * mapping and the kernel identity mapping share the same
+ * page-table pages. Thus we can't really use different
+ * protections for the kernel text and identity mappings. Also,
+ * these shared mappings are made of small page mappings.
+ * Thus this don't enforce !RW mapping for small page kernel
+ * text mapping logic will help Linux Xen parvirt guest boot
+ * aswell.
+ */
+ if (lookup_address(address, &level) && (level != PG_LEVEL_4K))
+ pgprot_val(forbidden) |= _PAGE_RW;
+ }
#endif
prot = __pgprot(pgprot_val(prot) & ~pgprot_val(forbidden));