From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH] KVM: MMU: Disassociate direct maps from guest levels Date: Tue, 23 Mar 2010 13:02:35 +0200 Message-ID: <4BA89FCB.7000708@redhat.com> References: <1268554972-9827-1-git-send-email-avi@redhat.com> <20100317181625.GA10372@amt.cnet> <4BA89D23.1090005@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: Marcelo Tosatti , Joerg Roedel Return-path: Received: from mx1.redhat.com ([209.132.183.28]:31963 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751389Ab0CWLCi (ORCPT ); Tue, 23 Mar 2010 07:02:38 -0400 In-Reply-To: <4BA89D23.1090005@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 03/23/2010 12:51 PM, Avi Kivity wrote: > On 03/17/2010 08:16 PM, Marcelo Tosatti wrote: >> On Sun, Mar 14, 2010 at 10:22:52AM +0200, Avi Kivity wrote: >>> Direct maps are linear translations for a section of memory, used for >>> real mode or with large pages. As such, they are independent of the >>> guest >>> levels. >>> >>> Teach the mmu about this by making page->role.glevels = 0 for direct >>> maps. >>> This allows direct maps to be shared among real mode and the various >>> paging >>> modes. >>> >>> @@ -1328,6 +1328,8 @@ static struct kvm_mmu_page >>> *kvm_mmu_get_page(struct kvm_vcpu *vcpu, >>> role = vcpu->arch.mmu.base_role; >>> role.level = level; >>> role.direct = direct; >>> + if (role.direct) >>> + role.glevels = 0; >>> role.access = access; >>> if (vcpu->arch.mmu.root_level<= PT32_ROOT_LEVEL) { >>> quadrant = gaddr>> (PAGE_SHIFT + (PT64_PT_BITS * level)); >>> -- >>> 1.7.0.2 >> Isnt this what happens already, since for tdp base_role.glevels is not >> initialized? > > Correct. I was thinking about the nested npt case, which will use > role.glevels. Joerg, please incorporate this into your nnpt patchset. > Actually, incorrect. This patch is also applicable to non-tdp (which is the same case as nnpt). It will allow reusing real-mode direct maps and large page mappings from the various modes. It won't make any performance difference, it's more a documentation aid that direct maps aren't dependent on the guest at all, except for permissions. -- error compiling committee.c: too many arguments to function