From patchwork Mon May 8 15:47:56 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mathias Krause X-Patchwork-Id: 13234693 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 E1E10C77B75 for ; Mon, 8 May 2023 15:49:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234566AbjEHPtQ (ORCPT ); Mon, 8 May 2023 11:49:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59492 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234597AbjEHPtG (ORCPT ); Mon, 8 May 2023 11:49:06 -0400 Received: from mail-ej1-x635.google.com (mail-ej1-x635.google.com [IPv6:2a00:1450:4864:20::635]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0086FA5C4 for ; Mon, 8 May 2023 08:48:34 -0700 (PDT) Received: by mail-ej1-x635.google.com with SMTP id a640c23a62f3a-965f7bdab6bso636477866b.3 for ; Mon, 08 May 2023 08:48:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=grsecurity.net; s=grsec; t=1683560899; x=1686152899; 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=bUQiJBVRFOYwj3LFo9SqD7kqRZqQ+2PxKuM6BL7h40I=; b=Qfm6+G4WvzVL4wrVGrBvOtN403UmyKKYwxYYgKaEkA29qU3EzzjNXgmq03iV1V8h71 SqCK9fw/OojzEhmOzvGEFHvCQ00fFTm+hdpGYzsFLMQgAS/gkgx24bzx3xh21uMCmPVN ZELaHmpBnIXPwhP23WYRQuaqkb3VVrD5td6E5rrikmJsJuI3CaDHvRxoECGOTWhhwJJ8 QLS+1XYB+FasfYecpneaj5iK0eD1w2tzZ3rTozm36rXcpokp7i4CqkvmrjWS8YnpgcWW IH5FCeyXgsNPMGiEVD5O0MmLxKqrM8Zp9VvYuk6mHKFNo4ojmMA2+SnFh/w1a7oeWe6T KMcQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1683560899; x=1686152899; 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=bUQiJBVRFOYwj3LFo9SqD7kqRZqQ+2PxKuM6BL7h40I=; b=ewGuWTX28/LN223ZgnXa0Er5z0LgOlCd3SuqHggHUGweyjVnJYJthimFWX1UL32KQS AOY0jRskp7kp0ab2to8v0x/a/I49iz1vPjHvyB43SR10V1K41CpOidtAt9G7EVkSpkz+ VLWSfmf248r1ERrXdnfh8u7CL8xEBOOszQVR90YXtlN4VbO6hr5Fzfoeq2//1xL8/GVT yRDyzDKxurRKGKW/M/KgNYaH6iLR/xJD03JG6RK+mS+lCaa+CMJ7Ekg27DdI2+W5Ojfc ha+W7mWQu8cX9p8bA3Xdht3yNYcLx72DD27lv4szIFSaghe58KCIZz2wBQy1G80IUooB kA/g== X-Gm-Message-State: AC+VfDy32lIdqLgQ6wUA0Z+baf9hfGzm72sFcfcgJpKvHDbQmcDCHbv9 fMxDlgdfp+E4rMWXaRZ02fQZbw== X-Google-Smtp-Source: ACHHUZ51bGDLCusY1s0Fw64gaWk1STV7958l6+QhX6BFFSIn00DTnVNGi67ePeXiI6vOFYMh9Cbh9Q== X-Received: by 2002:a17:907:6eaa:b0:94f:81c:725e with SMTP id sh42-20020a1709076eaa00b0094f081c725emr11354436ejc.59.1683560898712; Mon, 08 May 2023 08:48:18 -0700 (PDT) Received: from localhost.localdomain (p549211c7.dip0.t-ipconnect.de. [84.146.17.199]) by smtp.gmail.com with ESMTPSA id k21-20020a170906055500b009584c5bcbc7sm126316eja.49.2023.05.08.08.48.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 May 2023 08:48:18 -0700 (PDT) From: Mathias Krause To: stable@vger.kernel.org Cc: Paolo Bonzini , Sean Christopherson , kvm@vger.kernel.org, Mathias Krause Subject: [PATCH 5.10 02/10] KVM: x86: Do not unload MMU roots when only toggling CR0.WP with TDP enabled Date: Mon, 8 May 2023 17:47:56 +0200 Message-Id: <20230508154804.30078-3-minipli@grsecurity.net> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230508154804.30078-1-minipli@grsecurity.net> References: <20230508154804.30078-1-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 # backport to v5.10.x --- - account for different kvm_init_mmu() arguments 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 7464ca3806fa..bd4d64c1bdf9 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -868,6 +868,18 @@ int kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0) kvm_x86_ops.set_cr0(vcpu, 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, false); + return 0; + } + if ((cr0 ^ old_cr0) & X86_CR0_PG) { kvm_clear_async_pf_completion_queue(vcpu); kvm_async_pf_hash_reset(vcpu);