path: root/arch
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authorIan Campbell <ian.campbell@citrix.com>2010-02-26 17:16:00 +0000
committerGreg Kroah-Hartman <gregkh@suse.de>2010-03-15 08:50:06 -0700
commit81a1448f6f77f2fbbc4b9be64167533d2e2181cf (patch)
treeac83eb9e72917aeee77dbf9379530b44925a9205 /arch
parent3f03f7afa01b26c17c226816ab6deb222209bb43 (diff)
x86, xen: Disable highmem PTE allocation even when CONFIG_HIGHPTE=y
commit 817a824b75b1475f1b067c8cee318c7b4d66fcde upstream. There's a path in the pagefault code where the kernel deliberately breaks its own locking rules by kmapping a high pte page without holding the pagetable lock (in at least page_check_address). This breaks Xen's ability to track the pinned/unpinned state of the page. There does not appear to be a viable workaround for this behaviour so simply disable HIGHPTE for all Xen guests. Signed-off-by: Ian Campbell <ian.campbell@citrix.com> LKML-Reference: <1267204562-11844-1-git-send-email-ian.campbell@citrix.com> Cc: Jeremy Fitzhardinge <jeremy@goop.org> Cc: Ingo Molnar <mingo@elte.hu> Cc: Pasi Kärkkäinen <pasik@iki.fi> Cc: <xen-devel@lists.xensource.com> Signed-off-by: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'arch')
2 files changed, 13 insertions, 5 deletions
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 79f97383cde3..3578688ab670 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -48,6 +48,7 @@
#include <asm/traps.h>
#include <asm/setup.h>
#include <asm/desc.h>
+#include <asm/pgalloc.h>
#include <asm/pgtable.h>
#include <asm/tlbflush.h>
#include <asm/reboot.h>
@@ -1092,6 +1093,12 @@ asmlinkage void __init xen_start_kernel(void)
__supported_pte_mask |= _PAGE_IOMAP;
+ /*
+ * Prevent page tables from being allocated in highmem, even
+ * if CONFIG_HIGHPTE is enabled.
+ */
+ __userpte_alloc_gfp &= ~__GFP_HIGHMEM;
#ifdef CONFIG_X86_64
/* Work out if we support NX */
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index bf4cd6bfe959..350a3deedf25 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1432,14 +1432,15 @@ static void *xen_kmap_atomic_pte(struct page *page, enum km_type type)
pgprot_t prot = PAGE_KERNEL;
+ /*
+ * We disable highmem allocations for page tables so we should never
+ * see any calls to kmap_atomic_pte on a highmem page.
+ */
+ BUG_ON(PageHighMem(page));
if (PagePinned(page))
- if (0 && PageHighMem(page))
- printk("mapping highpte %lx type %d prot %s\n",
- page_to_pfn(page), type,
- (unsigned long)pgprot_val(prot) & _PAGE_RW ? "WRITE" : "READ");
return kmap_atomic_prot(page, type, prot);