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=-12.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 7D22BC433E0 for ; Tue, 28 Jul 2020 21:36:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 569D620656 for ; Tue, 28 Jul 2020 21:36:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Crgl95u+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729484AbgG1VgE (ORCPT ); Tue, 28 Jul 2020 17:36:04 -0400 Received: from us-smtp-delivery-74.mimecast.com ([216.205.24.74]:29139 "EHLO us-smtp-delivery-74.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729322AbgG1VgE (ORCPT ); Tue, 28 Jul 2020 17:36:04 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1595972161; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=hFN4b/j5jaO54ZEzhfUAuV3x8q451AKAzH67obVUqYg=; b=Crgl95u+x3r3N7wzEtTR3vJE5qHXYIhz7ETrYjZt4Y/sHqU7UZQDZq1eV7HAjyeSnDKzpq Zd57uqdHYMXhVBHNkmlDMujqpJRefZ5TNS1Xm8kPEdAK2n4V+zsewwxtHu0O60XUzSL7QY X9Hs22gEd8SWdRMzHNyO4Uo8M1SbzD4= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-255-z_unr054P7KYIbBmz9HOGw-1; Tue, 28 Jul 2020 17:29:54 -0400 X-MC-Unique: z_unr054P7KYIbBmz9HOGw-1 Received: by mail-wm1-f69.google.com with SMTP id h205so317899wmf.0 for ; Tue, 28 Jul 2020 14:29:53 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=hFN4b/j5jaO54ZEzhfUAuV3x8q451AKAzH67obVUqYg=; b=I9CCj0pFlIqfyyN67MPzMyjqZ17y3liE7uDazRH8GJ5U9r9ZGQPLSvzp45CzR385Xe HTmIlBu02H7cFAEFHtOEsFfk1dav9frDB8/ReUToVBSeleRsZ0wgFhg5FaAY38l1dqXR IHzqilFvwLv3QPbzCchkb/fN51Mqje2jcsJD8ShPPQh4vDNhbj8LVndZHL1ri0AjgfSv 71CUNbGgsVi6wYMSwKmpxQuLscqkaKd5QXGDzf0x46FN95b6CfifaI1Iv5UD3FOC+14A Aeg++ZTFIyKPjbc12Vacq4WXsyoidmt5ZI4cspt3v4Kz5rooSUKKdvD5R6JA37DxnkFr 24WQ== X-Gm-Message-State: AOAM531prCJgTPBV0vKcmFqgfMbkO4M1neAP5YqabjJEpN3U8RyNTjby 6ItzSYFXjMmIMcHAykOsHR63oNHluRCaVGxfirqy7um0i3QIkhtgMoV/3S7iv+NlTIVCU+7WBfO d4zeWz7PTK9Ii X-Received: by 2002:a1c:660a:: with SMTP id a10mr5333234wmc.115.1595971792867; Tue, 28 Jul 2020 14:29:52 -0700 (PDT) X-Google-Smtp-Source: ABdhPJyv8RtkRgVb2UrBMPKjab2gkzX6HJ3ubcR3IAT+JjmgvuK2/IJZPY4tXrBYzqe1V8fNfHM1GA== X-Received: by 2002:a1c:660a:: with SMTP id a10mr5333161wmc.115.1595971791156; Tue, 28 Jul 2020 14:29:51 -0700 (PDT) Received: from [192.168.10.150] ([93.56.170.5]) by smtp.gmail.com with ESMTPSA id t17sm192845wmj.34.2020.07.28.14.29.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 28 Jul 2020 14:29:50 -0700 (PDT) Subject: Re: [kvm-unit-tests PATCH] cstart64: do not assume CR4 should be zero To: Sean Christopherson Cc: kvm@vger.kernel.org, Nadav Amit References: <20200715205235.13113-1-sean.j.christopherson@intel.com> From: Paolo Bonzini Message-ID: Date: Tue, 28 Jul 2020 23:29:49 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200715205235.13113-1-sean.j.christopherson@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 15/07/20 22:52, Sean Christopherson wrote: > Explicitly zero cr4 in prepare_64() instead of "zeroing" it in the > common enter_long_mode(). Clobbering cr4 in enter_long_mode() breaks > switch_to_5level(), which sets cr4.LA57 before calling enter_long_mode() > and obviously expects cr4 to be preserved. > > Fixes: d86ef58 ("cstart: do not assume CR4 starts as zero") > Cc: Nadav Amit > Cc: Paolo Bonzini > Signed-off-by: Sean Christopherson > --- > > Two lines of code, two bugs. I'm pretty sure Paolo should win some kind > of award. :-D Two lines of code, two bugs immediately before disappearing for two weeks. 2^3 paper bags... Paolo > x86/cstart64.S | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/x86/cstart64.S b/x86/cstart64.S > index 3ae98d3..2d16688 100644 > --- a/x86/cstart64.S > +++ b/x86/cstart64.S > @@ -175,8 +175,12 @@ prepare_64: > lgdt gdt64_desc > setup_segments > > + xor %eax, %eax > + mov %eax, %cr4 > + > enter_long_mode: > - mov $(1 << 5), %eax // pae > + mov %cr4, %eax > + bts $5, %eax // pae > mov %eax, %cr4 > > mov pt_root, %eax >