From 74260714c56de4f967fcb2f17a8656bc574b75be Mon Sep 17 00:00:00 2001 From: Jeremy Fitzhardinge Date: Tue, 16 Oct 2007 11:51:30 -0700 Subject: xen: lock pte pages while pinning/unpinning When a pagetable is created, it is made globally visible in the rmap prio tree before it is pinned via arch_dup_mmap(), and remains in the rmap tree while it is unpinned with arch_exit_mmap(). This means that other CPUs may race with the pinning/unpinning process, and see a pte between when it gets marked RO and actually pinned, causing any pte updates to fail with write-protect faults. As a result, all pte pages must be properly locked, and only unlocked once the pinning/unpinning process has finished. In order to avoid taking spinlocks for the whole pagetable - which may overflow the PREEMPT_BITS portion of preempt counter - it locks and pins each pte page individually, and then finally pins the whole pagetable. Signed-off-by: Jeremy Fitzhardinge Cc: Rik van Riel Cc: Hugh Dickens Cc: David Rientjes Cc: Andrew Morton Cc: Andi Kleen Cc: Keir Fraser Cc: Jan Beulich --- arch/x86/xen/enlighten.c | 30 +++++++++++++++++++++--------- 1 file changed, 21 insertions(+), 9 deletions(-) (limited to 'arch/x86/xen/enlighten.c') diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index e334bf7..4186cb6 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -666,6 +666,15 @@ static __init void xen_alloc_pt_init(struct mm_struct *mm, u32 pfn) make_lowmem_page_readonly(__va(PFN_PHYS(pfn))); } +static void pin_pagetable_pfn(unsigned level, unsigned long pfn) +{ + struct mmuext_op op; + op.cmd = level; + op.arg1.mfn = pfn_to_mfn(pfn); + if (HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF)) + BUG(); +} + /* This needs to make sure the new pte page is pinned iff its being attached to a pinned pagetable. */ static void xen_alloc_pt(struct mm_struct *mm, u32 pfn) @@ -675,9 +684,10 @@ static void xen_alloc_pt(struct mm_struct *mm, u32 pfn) if (PagePinned(virt_to_page(mm->pgd))) { SetPagePinned(page); - if (!PageHighMem(page)) + if (!PageHighMem(page)) { make_lowmem_page_readonly(__va(PFN_PHYS(pfn))); - else + pin_pagetable_pfn(MMUEXT_PIN_L1_TABLE, pfn); + } else /* make sure there are no stray mappings of this page */ kmap_flush_unused(); @@ -690,8 +700,10 @@ static void xen_release_pt(u32 pfn) struct page *page = pfn_to_page(pfn); if (PagePinned(page)) { - if (!PageHighMem(page)) + if (!PageHighMem(page)) { + pin_pagetable_pfn(MMUEXT_UNPIN_TABLE, pfn); make_lowmem_page_readwrite(__va(PFN_PHYS(pfn))); + } } } @@ -806,15 +818,15 @@ static __init void xen_pagetable_setup_done(pgd_t *base) /* Actually pin the pagetable down, but we can't set PG_pinned yet because the page structures don't exist yet. */ { - struct mmuext_op op; + unsigned level; + #ifdef CONFIG_X86_PAE - op.cmd = MMUEXT_PIN_L3_TABLE; + level = MMUEXT_PIN_L3_TABLE; #else - op.cmd = MMUEXT_PIN_L3_TABLE; + level = MMUEXT_PIN_L2_TABLE; #endif - op.arg1.mfn = pfn_to_mfn(PFN_DOWN(__pa(base))); - if (HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF)) - BUG(); + + pin_pagetable_pfn(level, PFN_DOWN(__pa(base))); } } -- cgit v1.1