From patchwork Fri Jul 15 23:00:13 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 12919897 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 AC037C433EF for ; Fri, 15 Jul 2022 23:00:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230218AbiGOXAZ (ORCPT ); Fri, 15 Jul 2022 19:00:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59648 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230047AbiGOXAX (ORCPT ); Fri, 15 Jul 2022 19:00:23 -0400 Received: from mail-pj1-x104a.google.com (mail-pj1-x104a.google.com [IPv6:2607:f8b0:4864:20::104a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BAC7F3C144 for ; Fri, 15 Jul 2022 16:00:21 -0700 (PDT) Received: by mail-pj1-x104a.google.com with SMTP id c18-20020a17090a8d1200b001ef85196fb4so5895463pjo.4 for ; Fri, 15 Jul 2022 16:00:21 -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=4mRUe9k6N29Y8TY671ys1SOzt46CXKbNlnzYh7VBMGg=; b=BY+ofGKbdhxI2uO5Nyqd5dE57NYG6j6ZefdgDGiAMMy15vVMXVMCrAxkz/HmhpImK+ Grv+x99LKg2/2a7c8R/phTxEvCikiuo0xcEF+jCO7cRYnO7Jz86w6MRWzcHiUpAcmpse 0iTfrjC1O28pwL1VrBCVYAXfp8Eo9G1UJBI8jOC23NXXn0vDG7ZLCMOn05PaeAjhfClh wO0w2V7+MZ1Bl/hlLPcPW45z8QlYCjNcKvOAYamGbWsL9h7BLrpWxBRhmOYPC/bkhtLM qUA7RMiIQSituv4YUDa3XRxArvCtVaN2kUHvfSpAQ6HYdnbb4MjeiIsma9YMnf6/n2C4 1sNA== 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=4mRUe9k6N29Y8TY671ys1SOzt46CXKbNlnzYh7VBMGg=; b=WFxlVkW3f2BJlrfjlU9Vhb36h/ah4RlooGLFwyyIXxl0uwhrELn64TJ+xjmt6FWz8T yt7y24cQT160/LurP5xq4Oz7jGzN4/RkFjTzyaQbrScactNLNHO7eNj8W9nLnGfvG96I 7HRgy2JYgBTQNucrahZ4X/EB/4hrSeNzm7AnoSp1/8qhfyD6DNkfGitvQvYqI9OKGS0X DAea0Xl2FaKY/gWcR3fPj0AkojnaEkwoVw9/LQ2ULDepDnSWUJ7ijTkVl/KxrjWXeqAJ SnbpEi+ffuPqzyoo6KCmUh4BXxbvPnpt0Fr0OivpgrvLr1kZv2+M7ZpjgZ2oQqaEWc45 Xb6w== X-Gm-Message-State: AJIora/NK0JlxUtQWs8uuIEfXnXDf6KfkWZo2N9IbsGgeyB+GfObFgAZ 4Gj3Y1fioxRt9EQPniuvIMiKIRVdyqE= X-Google-Smtp-Source: AGRyM1smbVwsZvafhg6YAk0nSxXgCOlfpSnfKN9p9HtlEhf/jQcGocWbnbcv1Ozn+bbDrtBXCdl//YT/YPo= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a17:902:d54b:b0:16b:eea4:77da with SMTP id z11-20020a170902d54b00b0016beea477damr15632782plf.45.1657926021275; Fri, 15 Jul 2022 16:00:21 -0700 (PDT) Reply-To: Sean Christopherson Date: Fri, 15 Jul 2022 23:00:13 +0000 In-Reply-To: <20220715230016.3762909-1-seanjc@google.com> Message-Id: <20220715230016.3762909-2-seanjc@google.com> Mime-Version: 1.0 References: <20220715230016.3762909-1-seanjc@google.com> X-Mailer: git-send-email 2.37.0.170.g444d1eabd0-goog Subject: [PATCH 1/4] KVM: x86: Reject loading KVM if host.PAT[0] != WB From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Reject KVM if entry '0' in the host's IA32_PAT MSR is not programmed to writeback (WB) memtype. KVM subtly relies on IA32_PAT entry '0' to be programmed to WB by leaving the PAT bits in shadow paging and NPT SPTEs as '0'. If something other than WB is in PAT[0], at _best_ guests will suffer very poor performance, and at worst KVM will crash the system by breaking cache-coherency expecations (e.g. using WC for guest memory). Signed-off-by: Sean Christopherson Reviewed-by: Maxim Levitsky --- arch/x86/kvm/x86.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index f389691d8c04..12199c40f2bc 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9141,6 +9141,7 @@ static struct notifier_block pvclock_gtod_notifier = { int kvm_arch_init(void *opaque) { struct kvm_x86_init_ops *ops = opaque; + u64 host_pat; int r; if (kvm_x86_ops.hardware_enable) { @@ -9179,6 +9180,20 @@ int kvm_arch_init(void *opaque) goto out; } + /* + * KVM assumes that PAT entry '0' encodes WB memtype and simply zeroes + * the PAT bits in SPTEs. Bail if PAT[0] is programmed to something + * other than WB. Note, EPT doesn't utilize the PAT, but don't bother + * with an exception. PAT[0] is set to WB on RESET and also by the + * kernel, i.e. failure indicates a kernel bug or broken firmware. + */ + if (rdmsrl_safe(MSR_IA32_CR_PAT, &host_pat) || + (host_pat & GENMASK(2, 0)) != 6) { + pr_err("kvm: host PAT[0] is not WB\n"); + r = -EIO; + goto out; + } + r = -ENOMEM; x86_emulator_cache = kvm_alloc_emulator_cache();