diff options
Diffstat (limited to 'virt/kvm')
| -rw-r--r-- | virt/kvm/kvm_main.c | 38 |
1 files changed, 14 insertions, 24 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 4286d4766510..f29abeb6a912 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -104,34 +104,24 @@ static pfn_t fault_pfn; inline int kvm_is_mmio_pfn(pfn_t pfn) { if (pfn_valid(pfn)) { - struct page *head; + int reserved; struct page *tail = pfn_to_page(pfn); - head = compound_head(tail); + struct page *head = compound_trans_head(tail); + reserved = PageReserved(head); if (head != tail) { - smp_rmb(); /* - * head may be a dangling pointer. - * __split_huge_page_refcount clears PageTail - * before overwriting first_page, so if - * PageTail is still there it means the head - * pointer isn't dangling. + * "head" is not a dangling pointer + * (compound_trans_head takes care of that) + * but the hugepage may have been splitted + * from under us (and we may not hold a + * reference count on the head page so it can + * be reused before we run PageReferenced), so + * we've to check PageTail before returning + * what we just read. */ - if (PageTail(tail)) { - /* - * the "head" is not a dangling - * pointer but the hugepage may have - * been splitted from under us (and we - * may not hold a reference count on - * the head page so it can be reused - * before we run PageReferenced), so - * we've to recheck PageTail before - * returning what we just read. - */ - int reserved = PageReserved(head); - smp_rmb(); - if (PageTail(tail)) - return reserved; - } + smp_rmb(); + if (PageTail(tail)) + return reserved; } return PageReserved(tail); } |