From nobody Tue Apr 7 07:06:55 2026 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 47124ECAAD5 for ; Tue, 30 Aug 2022 23:56:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229896AbiH3X4t (ORCPT ); Tue, 30 Aug 2022 19:56:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53846 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231828AbiH3X4U (ORCPT ); Tue, 30 Aug 2022 19:56:20 -0400 Received: from mail-pl1-x649.google.com (mail-pl1-x649.google.com [IPv6:2607:f8b0:4864:20::649]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D2B3354CA2 for ; Tue, 30 Aug 2022 16:55:56 -0700 (PDT) Received: by mail-pl1-x649.google.com with SMTP id m15-20020a170902db0f00b001753b1c5adeso882806plx.18 for ; Tue, 30 Aug 2022 16:55:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc; bh=y3kz8obqLBonD5tHztG2UKXsESWQEw13imz9n7vKM28=; b=QO4pr/OUWywfeGPew6Vl8vnqc3SYijsxKpAsnxfE5RTke1B7w5vPsYPaSlXahQSRM0 IFSjVWD2W8wZzhkPsUga2Qcy4LplXxzYUCdwOQa2fTzBcFfUmwDswKPc2KGBUp5hKseA 8jRRBhirZ1LvG1KiamPdIh/XZXfZQ4Lv6Syx6aZnoEZmL+WBGvq2MZUoSE6oKYbP7EQ0 hAwP/Hjnhd2/AgR1OYTOgk1cZsAulgKYVxH3dYIuLW0pTe1LMispqZh7Jq2cP4Vqm9tz Jk347ukWwIPKiPZJv5FY12eMr59Ss8UKeSIGU+ss+mtyFLw51QCHcsavhOdZTEllbWE/ DO8w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc; bh=y3kz8obqLBonD5tHztG2UKXsESWQEw13imz9n7vKM28=; b=QfZ8EbhwPaWO+RByqreRwuyByqRnoVFasVvTxX70xq0+GVkcs9kQSIMFJP8tdArqWS 1nhyRDgWRX818xBQ6LtdJvILGyXce75A6vKiOjBNBmwlhfWkmPeQORUVmB1jvLn6wcRV SGi0KHmZjB/NBPN3Mr13SGNvwjJVgFjxQCEXJ7berFGd50O/xTJOZmd/UWIjhkBtcMaF N8U2z6wULKZgKMpuKh93weqIGgAu50D4uUE5ZS4cmmgyNkhK8OT4vuQOGZk8kMwe59Dc m8HDyw6EZtIBV7XIGVMfQQROzhog8Pwe06pkd8pSOV3OcHu3mVrNxFg1vEJ85N4BmVIp aXrw== X-Gm-Message-State: ACgBeo3mrrLLEeOPuhHi2hcDDKixJezFqa8I319uvUX953MBBHWkEwIN YX3gcRlAEVsd5Ry8sKptF2waQhvSkfo= X-Google-Smtp-Source: AA6agR4HYZOMjM4W62nKOMIMchdSJkN3Hvv4lk2xn8FabErsvrvhPNo3yhKmT05mKEsy59hy1iNCMgt1VDI= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a17:90a:e558:b0:1fb:c4b7:1a24 with SMTP id ei24-20020a17090ae55800b001fbc4b71a24mr18202pjb.1.1661903754875; Tue, 30 Aug 2022 16:55:54 -0700 (PDT) Reply-To: Sean Christopherson Date: Tue, 30 Aug 2022 23:55:37 +0000 In-Reply-To: <20220830235537.4004585-1-seanjc@google.com> Mime-Version: 1.0 References: <20220830235537.4004585-1-seanjc@google.com> X-Mailer: git-send-email 2.37.2.672.g94769d06f0-goog Message-ID: <20220830235537.4004585-10-seanjc@google.com> Subject: [PATCH v4 9/9] KVM: x86/mmu: explicitly check nx_hugepage in disallowed_hugepage_adjust() From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, David Matlack , Mingwei Zhang , Yan Zhao , Ben Gardon Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 currently assumes that the NX huge page mitigation is the only scenario where KVM will force a shadow page instead of a huge page, and so unnecessarily keeps an existing shadow page instead of replacing it with 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. prior to commit 5ba7c4c6d1c7 ("KVM: x86/MMU: Zap non-leaf SPTEs when disabling dirty logging"), KVM would keep shadow pages after disabling dirty logging due to a live migration being canceled, resulting in degraded performance due to running with 4kb pages instead of huge pages. Although the dirty logging case is "fixed", that fix is coincidental, i.e. is an implementation detail, and there are other scenarios where KVM will zap leaf SPTEs. E.g. zapping leaf SPTEs in response to a host page migration (mmu_notifier invalidation) to create a huge page would yield a similar result; KVM would see the shadow-present non-leaf SPTE and assume a huge page is disallowed. Fixes: b8e8c8303ff2 ("kvm: mmu: ITLB_MULTIHIT mitigation") Reviewed-by: Ben Gardon Reviewed-by: David Matlack Signed-off-by: Mingwei Zhang [sean: use spte_to_child_sp(), massage changelog] Signed-off-by: Sean Christopherson --- arch/x86/kvm/mmu/mmu.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 4737da767a40..d1fc087f86bf 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -3102,6 +3102,11 @@ void disallowed_hugepage_adjust(struct kvm_page_faul= t *fault, u64 spte, int cur_ cur_level =3D=3D fault->goal_level && is_shadow_present_pte(spte) && !is_large_pte(spte)) { + u64 page_mask; + + if (!spte_to_child_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 @@ -3109,8 +3114,8 @@ 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 =3D KVM_PAGES_PER_HPAGE(cur_level) - - KVM_PAGES_PER_HPAGE(cur_level - 1); + page_mask =3D KVM_PAGES_PER_HPAGE(cur_level) - + KVM_PAGES_PER_HPAGE(cur_level - 1); fault->pfn |=3D fault->gfn & page_mask; fault->goal_level--; } --=20 2.37.2.672.g94769d06f0-goog