From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753544AbZBRNqq (ORCPT ); Wed, 18 Feb 2009 08:46:46 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751991AbZBRNqg (ORCPT ); Wed, 18 Feb 2009 08:46:36 -0500 Received: from mx2.redhat.com ([66.187.237.31]:32896 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751777AbZBRNqg (ORCPT ); Wed, 18 Feb 2009 08:46:36 -0500 Message-ID: <499C1158.7020401@redhat.com> Date: Wed, 18 Feb 2009 13:47:04 +0000 From: Avi Kivity User-Agent: Thunderbird 2.0.0.19 (X11/20090105) MIME-Version: 1.0 To: Joerg Roedel CC: Marcelo Tosatti , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/3] kvm mmu: alloc shadow pages with __GFP_ZERO References: <1234962540-7131-1-git-send-email-joerg.roedel@amd.com> <1234962540-7131-4-git-send-email-joerg.roedel@amd.com> In-Reply-To: <1234962540-7131-4-git-send-email-joerg.roedel@amd.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Joerg Roedel wrote: > Not using __GFP_ZERO when allocating shadow pages triggers the > assertion in the kvm_mmu_alloc_page() when MMU debugging is enabled. > > Signed-off-by: Joerg Roedel > --- > arch/x86/kvm/mmu.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c > index c90b4b2..d93ecec 100644 > --- a/arch/x86/kvm/mmu.c > +++ b/arch/x86/kvm/mmu.c > @@ -301,7 +301,7 @@ static int mmu_topup_memory_cache_page(struct kvm_mmu_memory_cache *cache, > if (cache->nobjs >= min) > return 0; > while (cache->nobjs < ARRAY_SIZE(cache->objects)) { > - page = alloc_page(GFP_KERNEL); > + page = alloc_page(GFP_KERNEL | __GFP_ZERO); > if (!page) > return -ENOMEM; > set_page_private(page, 0); > What is the warning? Adding __GFP_ZERO here will cause us to clear the page twice, which is wasteful. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.