From patchwork Mon May 8 15:45:59 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mathias Krause X-Patchwork-Id: 13234679 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 DCF2EC77B7F for ; Mon, 8 May 2023 15:46:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234612AbjEHPqh (ORCPT ); Mon, 8 May 2023 11:46:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56286 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234411AbjEHPq2 (ORCPT ); Mon, 8 May 2023 11:46:28 -0400 Received: from mail-ed1-x531.google.com (mail-ed1-x531.google.com [IPv6:2a00:1450:4864:20::531]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5CA6BA267 for ; Mon, 8 May 2023 08:46:13 -0700 (PDT) Received: by mail-ed1-x531.google.com with SMTP id 4fb4d7f45d1cf-50bc22805d3so7287784a12.1 for ; Mon, 08 May 2023 08:46:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=grsecurity.net; s=grsec; t=1683560772; x=1686152772; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=hcGjxFwn5C+DW/CBTpII+bmNf6QTkHSVvjbNFA7/wRQ=; b=me38dQUbEuiJ3i7HUhs23JsgD/VxjxUDU2zyDRbm25DkpQQThVNlDl5FREddxzENDf nqEzKRFs/Z6n6vG+Pm8dGMMwzz6cQY3raVTarLVRCWqZHgj9AksnO7739BYQr0wO7thX mWdTQ+/kwkbAhzagCSqYkkcYSwRSYMVqk4s3wPLlhQKh6+D8Gmm09YG8kJ56eyv/KPP/ 0rjCYNwegv1cAyQyq0EBOBjYUojLI9xlszTG6lQVipWjHMAwUNECiRQpZzjHIxHR4vuU XUq5ZTTFEY7D3PiBmmmewrWGfrrqt24duPx/WE5wvfEr50LtVWwMWavylss8lVUDw14K Rm0Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1683560772; x=1686152772; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=hcGjxFwn5C+DW/CBTpII+bmNf6QTkHSVvjbNFA7/wRQ=; b=dLf30xoU7ar3IzsOZ4P5U7c96pYl493irbLdNMmKERbjmu0Xb7ROYRxk4GUB6CsmdI fdDcXMfzizs2cvGA9PPxoiwrpUMStZ3Vy4faHQfREMc83q4kRKW5iDPQKhVGmlBMX9Vb Zvf8Sv6IwldHGPLb03xwNNy9uWFxslgssY4r8sI8VgdE+Q4sGlk28rHRPIRJo5fP965p MpJZCUmhC5vksbPZwyHnXPEvYPKQ8g1Z4JlKV7nt0n5fHBWrdrAUqla0ZIGZHTZOqxpX onhhU23Jh5rxyx40VtahF5QpV0NHbxWFhsR8FF5Z4ufX3QZUkKfcehZJl37dl/cGnYbP yRIw== X-Gm-Message-State: AC+VfDym4g+1/gf6TD0EKciPpw06HyD7HkgvqKuJKt9WwJJP5ZiG1Cfr SwuUfP312Vi+thqK6wwszcTlDg== X-Google-Smtp-Source: ACHHUZ5xlTT5G0Ab2nprbHr3ddC09SS1fs8kIWgpVZjp61JIcjx3+r7scNKxVmHUAlngG3OMCgNMTA== X-Received: by 2002:a05:6402:104f:b0:50b:c397:bbac with SMTP id e15-20020a056402104f00b0050bc397bbacmr9030003edu.29.1683560771839; Mon, 08 May 2023 08:46:11 -0700 (PDT) Received: from localhost.localdomain (p549211c7.dip0.t-ipconnect.de. [84.146.17.199]) by smtp.gmail.com with ESMTPSA id j19-20020aa7ca53000000b0050bc27a4967sm6213551edt.21.2023.05.08.08.46.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 May 2023 08:46:11 -0700 (PDT) From: Mathias Krause To: stable@vger.kernel.org Cc: Paolo Bonzini , Sean Christopherson , kvm@vger.kernel.org, Mathias Krause Subject: [PATCH 6.1 2/5] KVM: x86: Do not unload MMU roots when only toggling CR0.WP with TDP enabled Date: Mon, 8 May 2023 17:45:59 +0200 Message-Id: <20230508154602.30008-3-minipli@grsecurity.net> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230508154602.30008-1-minipli@grsecurity.net> References: <20230508154602.30008-1-minipli@grsecurity.net> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org [ Upstream commit 01b31714bd90be2784f7145bf93b7f78f3d081e1 ] There is no need to unload the MMU roots with TDP enabled when only CR0.WP has changed -- the paging structures are still valid, only the permission bitmap needs to be updated. One heavy user of toggling CR0.WP is grsecurity's KERNEXEC feature to implement kernel W^X. The optimization brings a huge performance gain for this case as the following micro-benchmark running 'ssdd 10 50000' from rt-tests[1] on a grsecurity L1 VM shows (runtime in seconds, lower is better): legacy TDP shadow kvm-x86/next@d8708b 8.43s 9.45s 70.3s +patch 5.39s 5.63s 70.2s For legacy MMU this is ~36% faster, for TDP MMU even ~40% faster. Also TDP and legacy MMU now both have a similar runtime which vanishes the need to disable TDP MMU for grsecurity. Shadow MMU sees no measurable difference and is still slow, as expected. [1] https://git.kernel.org/pub/scm/utils/rt-tests/rt-tests.git Signed-off-by: Mathias Krause Link: https://lore.kernel.org/r/20230322013731.102955-3-minipli@grsecurity.net Co-developed-by: Sean Christopherson Signed-off-by: Sean Christopherson Signed-off-by: Mathias Krause --- arch/x86/kvm/x86.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index ab09d292bded..496bb9a58273 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -910,6 +910,18 @@ EXPORT_SYMBOL_GPL(load_pdptrs); void kvm_post_set_cr0(struct kvm_vcpu *vcpu, unsigned long old_cr0, unsigned long cr0) { + /* + * CR0.WP is incorporated into the MMU role, but only for non-nested, + * indirect shadow MMUs. If TDP is enabled, the MMU's metadata needs + * to be updated, e.g. so that emulating guest translations does the + * right thing, but there's no need to unload the root as CR0.WP + * doesn't affect SPTEs. + */ + if (tdp_enabled && (cr0 ^ old_cr0) == X86_CR0_WP) { + kvm_init_mmu(vcpu); + return; + } + if ((cr0 ^ old_cr0) & X86_CR0_PG) { kvm_clear_async_pf_completion_queue(vcpu); kvm_async_pf_hash_reset(vcpu);