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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 9933CC433DF for ; Wed, 20 May 2020 21:09:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 67157207E8 for ; Wed, 20 May 2020 21:09:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="arYIx2dm" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728337AbgETVJ5 (ORCPT ); Wed, 20 May 2020 17:09:57 -0400 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:50638 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728023AbgETVJ5 (ORCPT ); Wed, 20 May 2020 17:09:57 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1590008995; 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=rljt0JKhDnaA5kYo7V7yvh9gpRilhTrRqKa1LMsBGTA=; b=arYIx2dmhwTfLofrXAow1qYu8OEbFWxRJIIDcWca1PMrBU1jrN++hzlwQc4jboGvEr54vc NbPq6P1j5BOdHw2CX8mgeXRZ5bGLiOmKUJz3PExeFjVnnqzwwhgDQoUCseEVhe4LCpW3tu YwYo+5f8L0XABIEYyG4INwxes2NWF2E= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-389-VzS7pN-BP9KFN01tPauI1A-1; Wed, 20 May 2020 17:09:53 -0400 X-MC-Unique: VzS7pN-BP9KFN01tPauI1A-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id F06B9107ACCA; Wed, 20 May 2020 21:09:52 +0000 (UTC) Received: from starship (unknown [10.35.206.28]) by smtp.corp.redhat.com (Postfix) with ESMTP id E3B1060C20; Wed, 20 May 2020 21:09:51 +0000 (UTC) Message-ID: <8747006dabe787d5b4945f4dd9c2e2923335d87c.camel@redhat.com> Subject: Re: [PATCH 2/2] kvm/x86: don't expose MSR_IA32_UMWAIT_CONTROL unconditionally From: Maxim Levitsky To: Paolo Bonzini , kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org Date: Thu, 21 May 2020 00:09:50 +0300 In-Reply-To: References: <20200520160740.6144-1-mlevitsk@redhat.com> <20200520160740.6144-3-mlevitsk@redhat.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.34.4 (3.34.4-1.fc31) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2020-05-20 at 23:05 +0200, Paolo Bonzini wrote: > On 20/05/20 18:07, Maxim Levitsky wrote: > > This msr is only available when the host supports WAITPKG feature. > > > > This breaks a nested guest, if the L1 hypervisor is set to ignore > > unknown msrs, because the only other safety check that the > > kernel does is that it attempts to read the msr and > > rejects it if it gets an exception. > > > > Fixes: 6e3ba4abce KVM: vmx: Emulate MSR IA32_UMWAIT_CONTROL > > > > Signed-off-by: Maxim Levitsky > > --- > > arch/x86/kvm/x86.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > > index fe3a24fd6b263..9c507b32b1b77 100644 > > --- a/arch/x86/kvm/x86.c > > +++ b/arch/x86/kvm/x86.c > > @@ -5314,6 +5314,10 @@ static void kvm_init_msr_list(void) > > if (msrs_to_save_all[i] - MSR_ARCH_PERFMON_EVENTSEL0 >= > > min(INTEL_PMC_MAX_GENERIC, x86_pmu.num_counters_gp)) > > continue; > > + break; > > + case MSR_IA32_UMWAIT_CONTROL: > > + if (!kvm_cpu_cap_has(X86_FEATURE_WAITPKG)) > > + continue; > > default: > > break; > > } > > The patch is correct, and matches what is done for the other entries of > msrs_to_save_all. However, while looking at it I noticed that > X86_FEATURE_WAITPKG is actually never added, and that is because it was > also not added to the supported CPUID in commit e69e72faa3a0 ("KVM: x86: > Add support for user wait instructions", 2019-09-24), which was before > the kvm_cpu_cap mechanism was added. > > So while at it you should also fix that. The right way to do that is to > add a > > if (vmx_waitpkg_supported()) > kvm_cpu_cap_check_and_set(X86_FEATURE_WAITPKG); > > in vmx_set_cpu_caps. > > Thanks, Thank you very much for finding this. I didn't expect this to be broken. I will send a new version with this fix as well tomorrow. Best regards, Maxim Levitsky > > Paolo >