From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754195AbXLZLNs (ORCPT ); Wed, 26 Dec 2007 06:13:48 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751781AbXLZLGj (ORCPT ); Wed, 26 Dec 2007 06:06:39 -0500 Received: from il.qumranet.com ([82.166.9.18]:50470 "EHLO il.qumranet.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751776AbXLZLGG (ORCPT ); Wed, 26 Dec 2007 06:06:06 -0500 From: Avi Kivity To: linux-kernel@vger.kernel.org, kvm-devel@lists.sourceforge.net Cc: Anthony Liguori Subject: [PATCH 23/55] KVM: Fix gfn_to_page() acquiring mmap_sem twice Date: Wed, 26 Dec 2007 13:05:28 +0200 Message-Id: <1198667160-22953-24-git-send-email-avi@qumranet.com> X-Mailer: git-send-email 1.5.3.7 In-Reply-To: <1198667160-22953-1-git-send-email-avi@qumranet.com> References: <1198667160-22953-1-git-send-email-avi@qumranet.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Anthony Liguori KVM's nopage handler calls gfn_to_page() which acquires the mmap_sem when calling out to get_user_pages(). nopage handlers are already invoked with the mmap_sem held though. Introduce a __gfn_to_page() for use by the nopage handler which requires the lock to already be held. This was noticed by tglx. Signed-off-by: Anthony Liguori Signed-off-by: Avi Kivity --- drivers/kvm/kvm_main.c | 22 ++++++++++++++++++---- 1 files changed, 18 insertions(+), 4 deletions(-) diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c index c3dc24f..7186791 100644 --- a/drivers/kvm/kvm_main.c +++ b/drivers/kvm/kvm_main.c @@ -633,7 +633,10 @@ int kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn) } EXPORT_SYMBOL_GPL(kvm_is_visible_gfn); -struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn) +/* + * Requires current->mm->mmap_sem to be held + */ +static struct page *__gfn_to_page(struct kvm *kvm, gfn_t gfn) { struct kvm_memory_slot *slot; struct page *page[1]; @@ -648,12 +651,10 @@ struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn) return bad_page; } - down_read(¤t->mm->mmap_sem); npages = get_user_pages(current, current->mm, slot->userspace_addr + (gfn - slot->base_gfn) * PAGE_SIZE, 1, 1, 1, page, NULL); - up_read(¤t->mm->mmap_sem); if (npages != 1) { get_page(bad_page); return bad_page; @@ -661,6 +662,18 @@ struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn) return page[0]; } + +struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn) +{ + struct page *page; + + down_read(¤t->mm->mmap_sem); + page = __gfn_to_page(kvm, gfn); + up_read(¤t->mm->mmap_sem); + + return page; +} + EXPORT_SYMBOL_GPL(gfn_to_page); void kvm_release_page(struct page *page) @@ -2621,7 +2634,8 @@ static struct page *kvm_vm_nopage(struct vm_area_struct *vma, pgoff = ((address - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; if (!kvm_is_visible_gfn(kvm, pgoff)) return NOPAGE_SIGBUS; - page = gfn_to_page(kvm, pgoff); + /* current->mm->mmap_sem is already held so call lockless version */ + page = __gfn_to_page(kvm, pgoff); if (is_error_page(page)) { kvm_release_page(page); return NOPAGE_SIGBUS; -- 1.5.3.7