From 817a824b75b1475f1b067c8cee318c7b4d66fcde Mon Sep 17 00:00:00 2001 From: Ian Campbell Date: Fri, 26 Feb 2010 17:16:00 +0000 Subject: x86, xen: Disable highmem PTE allocation even when CONFIG_HIGHPTE=y MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 LKML-Reference: <1267204562-11844-1-git-send-email-ian.campbell@citrix.com> Cc: Jeremy Fitzhardinge Cc: Ingo Molnar Cc: Pasi Kärkkäinen Cc: # .32.x: 14315592: Allow highmem user page tables to be disabled at boot time Cc: # .32.x Cc: Signed-off-by: H. Peter Anvin --- 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 36daccb68642..b607239c1ba8 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -50,6 +50,7 @@ #include #include #include +#include #include #include #include @@ -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 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)) 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 -- cgit v1.2.1