Messages in this thread Patch in this message | | | Date | Fri, 12 Mar 2010 16:27:27 -0800 | From | Greg KH <> | Subject | [114/145] x86, xen: Disable highmem PTE allocation even when CONFIG_HIGHPTE=y |
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2.6.32-stable review patch. If anyone has any objections, please let me know.
---------------- From: Ian Campbell <ian.campbell@citrix.com>
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>
--- arch/x86/xen/enlighten.c | 7 +++++++ arch/x86/xen/mmu.c | 11 ++++++----- 2 files changed, 13 insertions(+), 5 deletions(-)
--- 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( __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 */ check_efer(); --- a/arch/x86/xen/mmu.c +++ b/arch/x86/xen/mmu.c @@ -1432,14 +1432,15 @@ static void *xen_kmap_atomic_pte(struct { 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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