From patchwork Sat Apr 9 00:38:47 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 12807306 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 054A5C433F5 for ; Sat, 9 Apr 2022 00:39:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240237AbiDIAl3 (ORCPT ); Fri, 8 Apr 2022 20:41:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33292 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240204AbiDIAlS (ORCPT ); Fri, 8 Apr 2022 20:41:18 -0400 Received: from mail-pg1-x54a.google.com (mail-pg1-x54a.google.com [IPv6:2607:f8b0:4864:20::54a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 243A3CA6F0 for ; Fri, 8 Apr 2022 17:39:01 -0700 (PDT) Received: by mail-pg1-x54a.google.com with SMTP id u3-20020a632343000000b0039cac94652aso5037484pgm.11 for ; Fri, 08 Apr 2022 17:39:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=reply-to:date:in-reply-to:message-id:mime-version:references :subject:from:to:cc; bh=U/xA/nSwurkGEdck/qaZkekmuGCzTuPGUBnd/eefe1E=; b=GRCcf0ghzrfbbfGPqwY8gcMpS9q954jGN54lbHMgexFfT28hQ7wCe/1fMEsMACZJLG wme9uxgGTLpC9IJ4eTZ4wcSG2DUeRLKZIkHNMncuDLYJ2/sTA6fTZlaY5U/tpm8Vu+30 rvBeNLWZkKtk1FS9FfiSLYHuPY6iRwRovKOEPPKgs8/Qcd4iXizLjzQ25wl8AE3SVwnC Ex8AR1Ibxo4/MBl9xzZKBDYnrd5V2bYSHlgsRaZEHyXqlBxjA1+1d83VrYtyQpY9dFJK W1J9cSDqLj0Nmsxdl/jbgT6p9P9IOIOR5SGAvkAfvqxUN/oERnvTlipraI97zVJdnQob Diwg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:reply-to:date:in-reply-to:message-id :mime-version:references:subject:from:to:cc; bh=U/xA/nSwurkGEdck/qaZkekmuGCzTuPGUBnd/eefe1E=; b=SXkepS+AacanZ4IDA2j+rxLpKvpX9TSYz99y97ZxQOT/prFKZ8E/GW22o2umP6o8+j NyAQCYIUYQS2iUwHaOK5iV2179o2WZC8qeD5/HpcvlbxXShkA+Grfkqjp73oplYboV6v suRj1M/aakcN4hhenqv/GSGaDu8DlRsgAQH2dmMOpja3F8KRJY+dQdjz4bpCrtvsy41n O9yVDKkjVCBuoeo0EJfffRwbeQ83zJXwNURrbIieGbIVQysx3eEcV/Aq8VxUOAePm//E jUtzjUXdel8k/G26giWIe6am+mP24swA+mJQzqFitLTUZ5P8Z8koPv+aZqDzAsxmug0K m0NA== X-Gm-Message-State: AOAM531YwX5HhSgnldUXSOE97wv2bX8eG/6sJiNgI2Frb6amPNkwgNmv fvvjajX86853IznREVx+k6+ELD7y8Sw= X-Google-Smtp-Source: ABdhPJzWm5cixOoYwZ2jCRkmulJdgu38wIoabB2kELlK12VuaYj5Ty1y/Ha2+rY56TAZL+3b/KTvyUsyzS4= X-Received: from seanjc.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:3e5]) (user=seanjc job=sendgmr) by 2002:a05:6a00:c94:b0:4fa:e134:4e6f with SMTP id a20-20020a056a000c9400b004fae1344e6fmr21792503pfv.66.1649464740605; Fri, 08 Apr 2022 17:39:00 -0700 (PDT) Reply-To: Sean Christopherson Date: Sat, 9 Apr 2022 00:38:47 +0000 In-Reply-To: <20220409003847.819686-1-seanjc@google.com> Message-Id: <20220409003847.819686-7-seanjc@google.com> Mime-Version: 1.0 References: <20220409003847.819686-1-seanjc@google.com> X-Mailer: git-send-email 2.35.1.1178.g4f1659d476-goog Subject: [PATCH 6/6] KVM: x86/mmu: explicitly check nx_hugepage in disallowed_hugepage_adjust() From: Sean Christopherson To: Paolo Bonzini Cc: Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Mingwei Zhang Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: Mingwei Zhang Explicitly check if a NX huge page is disallowed when determining if a page fault needs to be forced to use a smaller sized page. KVM incorrectly assumes that the NX huge page mitigation is the only scenario where KVM will create a shadow page instead of a huge page. Any scenario that causes KVM to zap leaf SPTEs may result in having a SP that can be made huge without violating the NX huge page mitigation. E.g. disabling of dirty logging, zapping from mmu_notifier due to page migration, guest MTRR changes that affect the viability of a huge page, etc... Fixes: b8e8c8303ff2 ("kvm: mmu: ITLB_MULTIHIT mitigation") Signed-off-by: Mingwei Zhang [sean: add barrier comments, use spte_to_sp()] Signed-off-by: Sean Christopherson --- arch/x86/kvm/mmu/mmu.c | 17 +++++++++++++++-- arch/x86/kvm/mmu/tdp_mmu.c | 6 ++++++ 2 files changed, 21 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 8b4f3550710a..c6f018c6d2f5 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -2908,6 +2908,19 @@ void disallowed_hugepage_adjust(struct kvm_page_fault *fault, u64 spte, int cur_ cur_level == fault->goal_level && is_shadow_present_pte(spte) && !is_large_pte(spte)) { + u64 page_mask; + + /* + * Ensure nx_huge_page_disallowed is read after checking for a + * present shadow page. A different vCPU may be concurrently + * installing the shadow page if mmu_lock is held for read. + * Pairs with the smp_wmb() in kvm_tdp_mmu_map(). + */ + smp_rmb(); + + if (!spte_to_sp(spte)->nx_huge_page_disallowed) + return; + /* * A small SPTE exists for this pfn, but FNAME(fetch) * and __direct_map would like to create a large PTE @@ -2915,8 +2928,8 @@ void disallowed_hugepage_adjust(struct kvm_page_fault *fault, u64 spte, int cur_ * patching back for them into pfn the next 9 bits of * the address. */ - u64 page_mask = KVM_PAGES_PER_HPAGE(cur_level) - - KVM_PAGES_PER_HPAGE(cur_level - 1); + page_mask = KVM_PAGES_PER_HPAGE(cur_level) - + KVM_PAGES_PER_HPAGE(cur_level - 1); fault->pfn |= fault->gfn & page_mask; fault->goal_level--; } diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index d0e6b341652c..5cae5cdcfcbc 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -1185,6 +1185,12 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) tdp_mmu_init_child_sp(sp, &iter); sp->nx_huge_page_disallowed = fault->huge_page_disallowed; + /* + * Ensure nx_huge_page_disallowed is visible before the + * SP is marked present, as mmu_lock is held for read. + * Pairs with the smp_rmb() in disallowed_hugepage_adjust(). + */ + smp_wmb(); if (tdp_mmu_link_sp(kvm, &iter, sp, true)) { tdp_mmu_free_sp(sp);