Ian Campbell
2010-Feb-26 17:16 UTC
[Xen-devel] [PATCH 1/3] xen: disable highmem PTE allocation even when CONFIG_HIGHPTE=y
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>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Pasi Kärkkäinen <pasik@iki.fi>
Cc: <stable@kernel.org> # .32.x: 14315592: Allow highmem user page tables
to be disabled at boot time
Cc: <stable@kernel.org> # .32.x
Cc: <xen-devel@lists.xensource.com>
---
arch/x86/xen/enlighten.c | 7 +++++++
arch/x86/xen/mmu.c | 11 ++++++-----
2 files changed, 13 insertions(+), 5 deletions(-)
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 36daccb..b607239 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -50,6 +50,7 @@
#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>
@@ -1094,6 +1095,12 @@ 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;
+
/* Work out if we support NX */
x86_configure_nx();
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index bf4cd6b..350a3de 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))
prot = PAGE_KERNEL_RO;
- 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);
}
#endif
--
1.5.6.5
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tip-bot for Ian Campbell
2010-Feb-27 23:51 UTC
[Xen-devel] [tip:x86/mm] x86, xen: Disable highmem PTE allocation even when CONFIG_HIGHPTE=y
Commit-ID: 817a824b75b1475f1b067c8cee318c7b4d66fcde
Gitweb: http://git.kernel.org/tip/817a824b75b1475f1b067c8cee318c7b4d66fcde
Author: Ian Campbell <ian.campbell@citrix.com>
AuthorDate: Fri, 26 Feb 2010 17:16:00 +0000
Committer: H. Peter Anvin <hpa@zytor.com>
CommitDate: Sat, 27 Feb 2010 14:41:01 -0800
x86, xen: Disable highmem PTE allocation even when CONFIG_HIGHPTE=y
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: <stable@kernel.org> # .32.x: 14315592: Allow highmem user page tables
to be disabled at boot time
Cc: <stable@kernel.org> # .32.x
Cc: <xen-devel@lists.xensource.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
---
arch/x86/xen/enlighten.c | 7 +++++++
arch/x86/xen/mmu.c | 11 ++++++-----
2 files changed, 13 insertions(+), 5 deletions(-)
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 36daccb..b607239 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -50,6 +50,7 @@
#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>
@@ -1094,6 +1095,12 @@ 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;
+
/* Work out if we support NX */
x86_configure_nx();
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index bf4cd6b..350a3de 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))
prot = PAGE_KERNEL_RO;
- 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);
}
#endif
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