From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DABE9C433ED for ; Wed, 19 May 2021 05:38:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BDD9560FF0 for ; Wed, 19 May 2021 05:38:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244485AbhESFjW (ORCPT ); Wed, 19 May 2021 01:39:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60442 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242154AbhESFhV (ORCPT ); Wed, 19 May 2021 01:37:21 -0400 Received: from mail-pg1-x52c.google.com (mail-pg1-x52c.google.com [IPv6:2607:f8b0:4864:20::52c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2E277C06134D for ; Tue, 18 May 2021 22:35:11 -0700 (PDT) Received: by mail-pg1-x52c.google.com with SMTP id y32so8627718pga.11 for ; Tue, 18 May 2021 22:35:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=ZnXQTZd4YFiMxjzLc+WeIPzH5Cugof+bDJeafEZszhA=; b=OWZHAZGSoROkzO2D07Qx34Q2pTN/VV2QPYjA6sI+a5Mzw19NU6NO1dGrrvlKE6jE/A f357jaHElfq3C8/Q5Li3LkEkQdZvPxtRHUJIJ8qR5wwUvrEH6w1fAdA//kgPzaCbGVwP qHZpdC89rPPqrRdX0NaV/a2hndUrexpx1e8A0omE5npzPx+TdVnEMHbfh6xpmATIt9SD z0ZUhz+Fxe0LTo5EckuZuaRNv661aK7wGkNcmTyw3/Cp6zR8c3bJ0HO8+P048SMQQDHg SlorePs2V97iUM+6qysZMOk6R+En8+SnbwZWwu3TRCKQFyGXvtPRs6YjzijP7hmBFv/s JmqA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=ZnXQTZd4YFiMxjzLc+WeIPzH5Cugof+bDJeafEZszhA=; b=oWZr1DR2ngQ0kEs1ucdMcQx515Vz4vqqMwol6304gld+OcNeuI0gYJ7nYdGLXRXAe6 2ulJDXUZVrUDV0aKu2b6lg+tBoH2qgHAA/f+Y3bxAhBNt9o/7Dk5M8404Oa24GHeLNMN XDXWoVbjslaXpy7m4ZscLTVTA67PzkpTcmZ2huWetqS6DU+QCKME7UDPsVi641fWNauV NqhvjPO62Cam1um0op7qle2wpQ98eEEPUfo4xX742C3CT3avtWNMcAnj2/CHwNow8D9H Eyybuw8h0laPqcSiAUXbtKBVf8lNAKbFWXfuPH4rfZNMWtvqaxoVCiOz2wEfjwAtcnql /Wrg== X-Gm-Message-State: AOAM530qHOD2f7DpvpDVG6u2eE8GWiUhqLtatLmgRmLNe1ctVk25ocUi 2H5mQ9/U3Y3L7ekNCUgVzt1wRivpmKOAUXooepaNIQ== X-Google-Smtp-Source: ABdhPJxRVRGQRmTOrx5g0fwZQ40vUC2OtgTmQ1h1QHlPsnFidYfsegpgCrqjFWNAVWbiD7CLjNy9sS0H5nOMl+lOapE= X-Received: by 2002:aa7:8c59:0:b029:28e:9093:cd4d with SMTP id e25-20020aa78c590000b029028e9093cd4dmr8891246pfd.25.1621402510627; Tue, 18 May 2021 22:35:10 -0700 (PDT) MIME-Version: 1.0 References: <20210424004645.3950558-1-seanjc@google.com> <20210424004645.3950558-23-seanjc@google.com> In-Reply-To: <20210424004645.3950558-23-seanjc@google.com> From: Reiji Watanabe Date: Tue, 18 May 2021 22:34:54 -0700 Message-ID: Subject: Re: [PATCH 22/43] KVM: VMX: Remove direct write to vcpu->arch.cr0 during vCPU RESET/INIT To: Sean Christopherson Cc: Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, Apr 23, 2021 at 5:51 PM Sean Christopherson wrote: > > Remove a bogus write to vcpu->arch.cr0 that immediately precedes > vmx_set_cr0() during vCPU RESET/INIT. For RESET, this is a nop since > the "old" CR0 value is meaningless. But for INIT, if the vCPU is coming > from paging enabled mode, crushing vcpu->arch.cr0 will cause the various > is_paging() checks in vmx_set_cr0() to get false negatives. > > For the exit_lmode() case, the false negative is benign as vmx_set_efer() > is called immediately after vmx_set_cr0(). > > For EPT without unrestricted guest, the false negative will cause KVM to > unnecessarily run with CR3 load/store exiting. But again, this is > benign, albeit sub-optimal. > > Signed-off-by: Sean Christopherson Reviewed-by: Reiji Watanabe