From 2462f42b4a59e316941637d9c8e4c6ee36b9fa08 Mon Sep 17 00:00:00 2001 From: Keir Fraser Date: Wed, 15 Dec 2010 12:12:15 +0000 Subject: [PATCH] x86/mm: fix up paging_mfn_is_dirty() Add locking, and don't allocate the top-level page if it's not there. Also gets rid of the default-to-1 case if there have been failed allocations because the safer thing is actually to return 0 and avoid modifying an un-dirtied page. Signed-off-by: Tim Deegan --- xen/arch/x86/mm/paging.c | 34 ++++++++++++++-------------------- 1 file changed, 14 insertions(+), 20 deletions(-) diff --git a/xen/arch/x86/mm/paging.c b/xen/arch/x86/mm/paging.c index 61d2e5fd2b..f429d0b337 100644 --- a/xen/arch/x86/mm/paging.c +++ b/xen/arch/x86/mm/paging.c @@ -311,51 +311,45 @@ int paging_mfn_is_dirty(struct domain *d, mfn_t gmfn) unsigned long pfn; mfn_t mfn, *l4, *l3, *l2; unsigned long *l1; - int rv; + int rv = 0; + log_dirty_lock(d); ASSERT(paging_mode_log_dirty(d)); /* We /really/ mean PFN here, even for non-translated guests. */ pfn = get_gpfn_from_mfn(mfn_x(gmfn)); - /* Page sharing not supported for shadow domains */ - BUG_ON(SHARED_M2P(pfn)); - if ( unlikely(!VALID_M2P(pfn)) ) - return 0; - - if ( d->arch.paging.log_dirty.failed_allocs > 0 ) - /* If we have any failed allocations our dirty log is bogus. - * Since we can't signal an error here, be conservative and - * report "dirty" in this case. (The only current caller, - * _sh_propagate, leaves known-dirty pages writable, preventing - * subsequent dirty-logging faults from them.) - */ - return 1; + /* Shared pages are always read-only; invalid pages can't be dirty. */ + if ( unlikely(SHARED_M2P(pfn) || !VALID_M2P(pfn)) ) + goto out; - l4 = paging_map_log_dirty_bitmap(d); - if ( !l4 ) - return 0; + mfn = d->arch.paging.log_dirty.top; + if ( !mfn_valid(mfn) ) + goto out; + l4 = map_domain_page(mfn_x(mfn)); mfn = l4[L4_LOGDIRTY_IDX(pfn)]; unmap_domain_page(l4); if ( !mfn_valid(mfn) ) - return 0; + goto out; l3 = map_domain_page(mfn_x(mfn)); mfn = l3[L3_LOGDIRTY_IDX(pfn)]; unmap_domain_page(l3); if ( !mfn_valid(mfn) ) - return 0; + goto out; l2 = map_domain_page(mfn_x(mfn)); mfn = l2[L2_LOGDIRTY_IDX(pfn)]; unmap_domain_page(l2); if ( !mfn_valid(mfn) ) - return 0; + goto out; l1 = map_domain_page(mfn_x(mfn)); rv = test_bit(L1_LOGDIRTY_IDX(pfn), l1); unmap_domain_page(l1); +out: + log_dirty_unlock(d); return rv; } -- 2.30.2