From patchwork Fri Mar 25 13:19:36 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Xiao Guangrong X-Patchwork-Id: 8671501 Return-Path: X-Original-To: patchwork-kvm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 19251C0553 for ; Fri, 25 Mar 2016 13:30:25 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 34ACA20254 for ; Fri, 25 Mar 2016 13:30:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 46CAB2034A for ; Fri, 25 Mar 2016 13:30:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753120AbcCYNaB (ORCPT ); Fri, 25 Mar 2016 09:30:01 -0400 Received: from mga09.intel.com ([134.134.136.24]:46976 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751683AbcCYN3A (ORCPT ); Fri, 25 Mar 2016 09:29:00 -0400 Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga102.jf.intel.com with ESMTP; 25 Mar 2016 06:28:58 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.24,391,1455004800"; d="scan'208";a="73118587" Received: from xiaoreal1.sh.intel.com (HELO xiaoreal1.sh.intel.com.sh.intel.com) ([10.239.48.79]) by fmsmga004.fm.intel.com with ESMTP; 25 Mar 2016 06:28:57 -0700 From: Xiao Guangrong To: pbonzini@redhat.com Cc: gleb@kernel.org, mtosatti@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Xiao Guangrong Subject: [PATCH 2/4] KVM: MMU: simplify the logic of __mmu_unsync_walk() Date: Fri, 25 Mar 2016 21:19:36 +0800 Message-Id: <1458911978-19430-2-git-send-email-guangrong.xiao@linux.intel.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1458911978-19430-1-git-send-email-guangrong.xiao@linux.intel.com> References: <1458911978-19430-1-git-send-email-guangrong.xiao@linux.intel.com> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Spam-Status: No, score=-7.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Each time i looked into the logic of walking unsync shadow pages, it costs lots of time to understand what it is doing. The trick of this logic is that the item, sp and idx, saved to kvm_mmu_pages is the sp and the index in the _parent_ level and it lacks any comment to explain this fact This patch simplifies it by saving the sp and its index to kvm_mmu_pages, then it is much easier to understand the operations on the its index Signed-off-by: Xiao Guangrong --- arch/x86/kvm/mmu.c | 40 ++++++++++++++++++++++------------------ 1 file changed, 22 insertions(+), 18 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 6bdfbc2..e273144 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -1830,6 +1830,8 @@ static inline void clear_unsync_child_bit(struct kvm_mmu_page *sp, int idx) __clear_bit(idx, sp->unsync_child_bitmap); } +#define INVALID_INDEX (-1) + static int __mmu_unsync_walk(struct kvm_mmu_page *sp, struct kvm_mmu_pages *pvec) { @@ -1846,10 +1848,10 @@ static int __mmu_unsync_walk(struct kvm_mmu_page *sp, child = page_header(ent & PT64_BASE_ADDR_MASK); - if (child->unsync_children) { - if (mmu_pages_add(pvec, child, i)) - return -ENOSPC; + if (mmu_pages_add(pvec, sp, i)) + return -ENOSPC; + if (child->unsync_children) { ret = __mmu_unsync_walk(child, pvec); if (!ret) { clear_unsync_child_bit(sp, i); @@ -1860,7 +1862,13 @@ static int __mmu_unsync_walk(struct kvm_mmu_page *sp, return ret; } else if (child->unsync) { nr_unsync_leaf++; - if (mmu_pages_add(pvec, child, i)) + + /* + * the unsync is on the last level so its 'idx' is + * useless, we set it to INVALID_INDEX to catch + * potential bugs. + */ + if (mmu_pages_add(pvec, child, INVALID_INDEX)) return -ENOSPC; } else clear_unsync_child_bit(sp, i); @@ -1869,8 +1877,6 @@ static int __mmu_unsync_walk(struct kvm_mmu_page *sp, return nr_unsync_leaf; } -#define INVALID_INDEX (-1) - static int mmu_unsync_walk(struct kvm_mmu_page *sp, struct kvm_mmu_pages *pvec) { @@ -1878,7 +1884,6 @@ static int mmu_unsync_walk(struct kvm_mmu_page *sp, if (!sp->unsync_children) return 0; - mmu_pages_add(pvec, sp, INVALID_INDEX); return __mmu_unsync_walk(sp, pvec); } @@ -1994,16 +1999,18 @@ static int mmu_pages_next(struct kvm_mmu_pages *pvec, { int n; - for (n = i+1; n < pvec->nr; n++) { + for (n = i + 1; n < pvec->nr; n++) { struct kvm_mmu_page *sp = pvec->page[n].sp; unsigned idx = pvec->page[n].idx; int level = sp->role.level; - parents->idx[level-1] = idx; - if (level == PT_PAGE_TABLE_LEVEL) + if (level == PT_PAGE_TABLE_LEVEL) { + WARN_ON(idx != INVALID_INDEX); break; + } - parents->parent[level-2] = sp; + parents->idx[level - 2] = idx; + parents->parent[level - 2] = sp; } return n; @@ -2018,19 +2025,16 @@ static int mmu_pages_first(struct kvm_mmu_pages *pvec, if (pvec->nr == 0) return 0; - WARN_ON(pvec->page[0].idx != INVALID_INDEX); - sp = pvec->page[0].sp; level = sp->role.level; WARN_ON(level == PT_PAGE_TABLE_LEVEL); - parents->parent[level-2] = sp; - - /* Also set up a sentinel. Further entries in pvec are all + /* + * Also set up a sentinel. Further entries in pvec are all * children of sp, so this element is never overwritten. */ - parents->parent[level-1] = NULL; - return mmu_pages_next(pvec, parents, 0); + parents->parent[level - 1] = NULL; + return mmu_pages_next(pvec, parents, -1); } static void mmu_pages_clear_parents(struct mmu_page_path *parents)