From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757175AbZC2Ncc (ORCPT ); Sun, 29 Mar 2009 09:32:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753202AbZC2NcV (ORCPT ); Sun, 29 Mar 2009 09:32:21 -0400 Received: from 8bytes.org ([88.198.83.132]:45268 "EHLO 8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751782AbZC2NcV (ORCPT ); Sun, 29 Mar 2009 09:32:21 -0400 Date: Sun, 29 Mar 2009 15:32:18 +0200 From: Joerg Roedel To: Avi Kivity Cc: Joerg Roedel , Marcelo Tosatti , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/7] kvm mmu: implement necessary data structures for second huge page accounting Message-ID: <20090329133218.GL31080@8bytes.org> References: <1238164319-16092-1-git-send-email-joerg.roedel@amd.com> <1238164319-16092-5-git-send-email-joerg.roedel@amd.com> <49CF5F68.1020507@redhat.com> <20090329130353.GK31080@8bytes.org> <49CF745B.5010001@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <49CF745B.5010001@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Mar 29, 2009 at 04:15:07PM +0300, Avi Kivity wrote: > Joerg Roedel wrote: >>> >>>> +static int has_wrprotected_largepage(struct kvm *kvm, gfn_t gfn) >>>> +{ >>>> + struct kvm_memory_slot *slot; >>>> + int *hugepage_idx; >>>> + >>>> + gfn = unalias_gfn(kvm, gfn); >>>> + slot = gfn_to_memslot_unaliased(kvm, gfn); >>>> + if (slot) { >>>> + hugepage_idx = slot_hugepage_idx(gfn, slot); >>>> >>> slot_largepage_idx() here? >>> >>> I don't think we ever write protect large pages, so why is this needed? >>> >> >> For 2mb pages we need to check if there is a write-protected 4k page in it >> before we map a 2mb page for writing. If there is any write-protected 4k >> page in a 2mb area this 2mb page is considered write-protected. These >> 'write-protected' 2mb pages are accounted in the account_shadow() >> function. This information is taken into account when we decide if we >> can map a guest 1gb page as a 1gb page on the host too. >> > > account_shadowed() actually increments a hugepage write_count by 1 for > every 4K page, not 2M page, if I read the code correctly. The code I > commented on is right though. > > The naming is confusing. I suggest > has_wrprotected_page_in_{large,huge}page(). although with the a level > parameter we can keep has_wrprotected_page(). Yeah true, the name is a bit confusing. I think a level parameter for has_wrprotected_page() is the best solution. Joerg