From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933451Ab2GCGcZ (ORCPT ); Tue, 3 Jul 2012 02:32:25 -0400 Received: from e23smtp03.au.ibm.com ([202.81.31.145]:46965 "EHLO e23smtp03.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933432Ab2GCGcY (ORCPT ); Tue, 3 Jul 2012 02:32:24 -0400 Message-ID: <4FF291EE.7060408@linux.vnet.ibm.com> Date: Tue, 03 Jul 2012 14:32:14 +0800 From: Xiao Guangrong User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120605 Thunderbird/13.0 MIME-Version: 1.0 To: Xiao Guangrong CC: Avi Kivity , Marcelo Tosatti , LKML , KVM Subject: [PATCH 3/3] KVM: MMU: track the refcount when unmap the page References: <4FF291A5.5090803@linux.vnet.ibm.com> In-Reply-To: <4FF291A5.5090803@linux.vnet.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit x-cbid: 12070220-6102-0000-0000-000001CEFC12 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org It will trigger a WARN_ON if the page has been freed but it is still used in mmu, it can help us to detect mm bug early Signed-off-by: Xiao Guangrong --- arch/x86/kvm/mmu.c | 8 ++++++++ 1 files changed, 8 insertions(+), 0 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index cac3408..af7e076 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -527,6 +527,14 @@ static int mmu_spte_clear_track_bits(u64 *sptep) return 0; pfn = spte_to_pfn(old_spte); + + /* + * KVM does not hold the refcount of the page used by + * kvm mmu, before reclaiming the page, we should + * unmap it from mmu first. + */ + WARN_ON(!page_count(pfn_to_page(pfn))); + if (!shadow_accessed_mask || old_spte & shadow_accessed_mask) kvm_set_pfn_accessed(pfn); if (!shadow_dirty_mask || (old_spte & shadow_dirty_mask)) -- 1.7.7.6