From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-23.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 235AAC433ED for ; Wed, 5 May 2021 17:35:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E499F606A5 for ; Wed, 5 May 2021 17:35:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236156AbhEERgK (ORCPT ); Wed, 5 May 2021 13:36:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50470 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240655AbhEERbx (ORCPT ); Wed, 5 May 2021 13:31:53 -0400 Received: from mail-ej1-x631.google.com (mail-ej1-x631.google.com [IPv6:2a00:1450:4864:20::631]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C846BC04957F for ; Wed, 5 May 2021 10:01:35 -0700 (PDT) Received: by mail-ej1-x631.google.com with SMTP id r9so3986498ejj.3 for ; Wed, 05 May 2021 10:01:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=dHdYz151PKTWNs0iwW3G2S7ao71/OuX/lBcR18Vu17c=; b=Vn5O+RKhScbNYISKD9Qxf/ZHZMGkFGOrAeHmD389mgDKKu1o1SSgJbZnABvWAy1zK8 RJ7uEYZnFXavtksWdsnGRNizBcTxLSogY5L+PiS9BJm0sVxgWh+Zp5zANxMhWJQWdph+ yU4k2PoxDqy455e3McohgsEfshFG7twShBqdJA2AQZ2lhjRk96jzehH2KgkU+d7KNj3o EIoDe2gljyWesUE+MNhGl50Gm8oB5E1njXk4l9FhSE414DN7K1DjMm4e8pE1kbZfEaPe J84FGlfuiw6XgLJxXPF73dmZOnjDiAlov8AHURk5VwS9Lp0J/rUHWPiU0U7zsW9RWVLB GTeg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=dHdYz151PKTWNs0iwW3G2S7ao71/OuX/lBcR18Vu17c=; b=jqDNpxSSjQDedKENFlEoQ8GVj4iSco3tK18FF6DphDYh7+ziy35eE+EYTLn4Fhcrib djBdOpeT/jE5z/fpaKi1XNh9iIugml5onIPVRCILBLiA5FP9tWb6Sj5Q9xT4V+LMSgMK FlK3Z9tu+m9ayxbtx7d8nM3uMTEqyVTxt82sNL2qDi1mf+kY/585gvfOYLxILth5WOA/ pY2e22cYTAvvcMg1Tif0Ss7rinj8FHKq16KNUWd3YpmH1f5+5UEZYxDOmOxAG00oYKyR KDxzhxZfKJyethYfSGB/kjWYF6UMREecSnrebynknlsTVUIpB5myjQwH08OVa+W6pSJy 7obQ== X-Gm-Message-State: AOAM5339vCk/NeY+nrhyr1tRMJjTOHsvvLi+vf6PuGCeY2gtKyd4X+8o 28aQ78z1tCT/v65DIudqti0KV0A3VXgt0EQ5ll/9VQ== X-Google-Smtp-Source: ABdhPJzmV2+raeJouq5W3ix1ojmG6vTXiEz8csQID7kNdSDeY0I/l2PTI5vlWjeCNwgfd+qp66HSwaw/ysJB3ni1NdA= X-Received: by 2002:a17:906:4c82:: with SMTP id q2mr28789124eju.80.1620234093994; Wed, 05 May 2021 10:01:33 -0700 (PDT) MIME-Version: 1.0 References: <817eae486273adad0a622671f628c5a99b72a375.1620200410.git.kai.huang@intel.com> In-Reply-To: From: Ben Gardon Date: Wed, 5 May 2021 10:01:22 -0700 Message-ID: Subject: Re: [PATCH 3/3] KVM: x86/mmu: Fix TDP MMU page table level To: Kai Huang Cc: kvm , Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, May 5, 2021 at 9:28 AM Ben Gardon wrote: > > On Wed, May 5, 2021 at 2:38 AM Kai Huang wrote: > > > > TDP MMU iterator's level is identical to page table's actual level. For > > instance, for the last level page table (whose entry points to one 4K > > page), iter->level is 1 (PG_LEVEL_4K), and in case of 5 level paging, > > the iter->level is mmu->shadow_root_level, which is 5. However, struct > > kvm_mmu_page's level currently is not set correctly when it is allocated > > in kvm_tdp_mmu_map(). When iterator hits non-present SPTE and needs to > > allocate a new child page table, currently iter->level, which is the > > level of the page table where the non-present SPTE belongs to, is used. > > This results in struct kvm_mmu_page's level always having its parent's > > level (excpet root table's level, which is initialized explicitly using > > mmu->shadow_root_level). This is kinda wrong, and not consistent with > > existing non TDP MMU code. Fortuantely the sp->role.level is only used > > in handle_removed_tdp_mmu_page(), which apparently is already aware of > > this, and handles correctly. However to make it consistent with non TDP > > MMU code (and fix the issue that both root page table and any child of > > it having shadow_root_level), fix this by using iter->level - 1 in > > kvm_tdp_mmu_map(). Also modify handle_removed_tdp_mmu_page() to handle > > such change. > > Ugh. Thank you for catching this. This is going to take me a bit to > review as I should audit the code more broadly for this problem in the > TDP MMU. > It would probably also be a good idea to add a comment on the level > field to say that it represents the level of the SPTEs in the > associated page, not the level of the SPTE that links to the > associated page. > Hopefully that will prevent similar future misunderstandings. I went through and manually audited the code. I think the only case that needs to be added to this is for nx recovery: --- a/arch/x86/kvm/mmu/tdp_mmu.h +++ b/arch/x86/kvm/mmu/tdp_mmu.h @@ -31,7 +31,7 @@ static inline bool kvm_tdp_mmu_zap_gfn_range(struct kvm *kvm, int as_id, } static inline bool kvm_tdp_mmu_zap_sp(struct kvm *kvm, struct kvm_mmu_page *sp) { - gfn_t end = sp->gfn + KVM_PAGES_PER_HPAGE(sp->role.level); + gfn_t end = sp->gfn + KVM_PAGES_PER_HPAGE(sp->role.level + 1); /* * Don't allow yielding, as the caller may have a flush pending. Note, Otherwise we won't zap the full page with this change, resulting in ineffective or less reliable NX recovery. > > > > > Signed-off-by: Kai Huang > > --- > > arch/x86/kvm/mmu/tdp_mmu.c | 8 ++++---- > > 1 file changed, 4 insertions(+), 4 deletions(-) > > > > diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c > > index debe8c3ec844..bcfb87e1c06e 100644 > > --- a/arch/x86/kvm/mmu/tdp_mmu.c > > +++ b/arch/x86/kvm/mmu/tdp_mmu.c > > @@ -335,7 +335,7 @@ static void handle_removed_tdp_mmu_page(struct kvm *kvm, tdp_ptep_t pt, > > > > for (i = 0; i < PT64_ENT_PER_PAGE; i++) { > > sptep = rcu_dereference(pt) + i; > > - gfn = base_gfn + (i * KVM_PAGES_PER_HPAGE(level - 1)); > > + gfn = base_gfn + i * KVM_PAGES_PER_HPAGE(level); > > > > if (shared) { > > /* > > @@ -377,12 +377,12 @@ static void handle_removed_tdp_mmu_page(struct kvm *kvm, tdp_ptep_t pt, > > WRITE_ONCE(*sptep, REMOVED_SPTE); > > } > > handle_changed_spte(kvm, kvm_mmu_page_as_id(sp), gfn, > > - old_child_spte, REMOVED_SPTE, level - 1, > > + old_child_spte, REMOVED_SPTE, level, > > shared); > > } > > > > kvm_flush_remote_tlbs_with_address(kvm, gfn, > > - KVM_PAGES_PER_HPAGE(level)); > > + KVM_PAGES_PER_HPAGE(level + 1)); > > > > call_rcu(&sp->rcu_head, tdp_mmu_free_sp_rcu_callback); > > } > > @@ -1009,7 +1009,7 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code, > > } > > > > if (!is_shadow_present_pte(iter.old_spte)) { > > - sp = alloc_tdp_mmu_page(vcpu, iter.gfn, iter.level); > > + sp = alloc_tdp_mmu_page(vcpu, iter.gfn, iter.level - 1); > > child_pt = sp->spt; > > > > new_spte = make_nonleaf_spte(child_pt, > > -- > > 2.31.1 > >