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=-14.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,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 91B87C3A5A1 for ; Thu, 22 Aug 2019 17:59:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5A46F2089E for ; Thu, 22 Aug 2019 17:59:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="nQFlsMCN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732381AbfHVR7A (ORCPT ); Thu, 22 Aug 2019 13:59:00 -0400 Received: from mail-io1-f66.google.com ([209.85.166.66]:46434 "EHLO mail-io1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731583AbfHVR7A (ORCPT ); Thu, 22 Aug 2019 13:59:00 -0400 Received: by mail-io1-f66.google.com with SMTP id x4so13619407iog.13 for ; Thu, 22 Aug 2019 10:58:59 -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=iXUFpwgRMQAkXsVfvJV1TUf/CGJ/vagejuy2962A3p8=; b=nQFlsMCNIXyiVhnrHPDUzScyZZTVDrU/VlfmSVvVDt/Var8ppF8oh87Kreshfxzksv BeLS3mMJy8mtzum9T2SPG9HeGMBOVmlW/TkLIrH+njTGpcMtyryLfSlYBs7CvnE8QRKE +kSI7EbBdgNZ1qKr1k13fwR+qWQ/vKMzX3qUh+wbKZE+9FnprzIVhvXYJ/ZOnHb/aBbi ov/5ngyFM6BpM0ThAyIrx4dAl1gADLRdw6zI8ZHEGrml04SoPn9cTlzRcw+WsMSZ3MV5 T/QP1x3gLPv+LWFB32W7mruEPZ1C/CdPCbcbymqF8KPB5AKxW9kOEiu8UcSslFQEXReW TJAQ== 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=iXUFpwgRMQAkXsVfvJV1TUf/CGJ/vagejuy2962A3p8=; b=b79EImchN50kYJGd56ZibSlQTeL/+svXb9RHYmkDNDHSZrPtsxGa5qPE5YK2t+qozz 85lRw6B5b+DVObVI5nrenF4ng2QxyP+qCBkXJuCSPv378bW+fw8tBQEwPA5QMCO05rnM YhnJYl6+ndYrsD/Ku840fRB00Li6ha9DvCzpd37sajkoAKJJzdxCTk13r1ULbwuDNzHw c+hfeaYvaLNwXiE7j6p9J1h7c2w+qZD/JmJlscpEKBG4l7FmRoDB25k8AFpkiwigdytM /GuHchaf5CWoBfct2moxRpG/5lu0VV/ffjz1PmAltV7uwg9YNSnTWdp9qySuC+mgcNdf Uquw== X-Gm-Message-State: APjAAAUM2T7AA77Gowt/6bIXfwh2ThskF2HH7RrVTr6SbFCGWnvd5LM0 ydvmYh4jXaZU+pfijhfAQIc7LI+uke0D23qXj5gAuh9V1pvGFA== X-Google-Smtp-Source: APXvYqxF6bfGevFIJzv3TWYOTFa61ZdWV4AOXNBTCzzBp93v8tUpvKD4WKXIMvanx8T3SmNDyMvmJWMx9i8Sm+F0j8I= X-Received: by 2002:a02:c65a:: with SMTP id k26mr831793jan.18.1566496738916; Thu, 22 Aug 2019 10:58:58 -0700 (PDT) MIME-Version: 1.0 References: <20190819214650.41991-1-nikita.leshchenko@oracle.com> <20190819214650.41991-2-nikita.leshchenko@oracle.com> In-Reply-To: <20190819214650.41991-2-nikita.leshchenko@oracle.com> From: Jim Mattson Date: Thu, 22 Aug 2019 10:58:47 -0700 Message-ID: Subject: Re: [PATCH 1/2] KVM: nVMX: Always indicate HLT activity support in VMX_MISC MSR To: Nikita Leshenko Cc: kvm list , Liran Alon , Krish Sadhukhan Content-Type: text/plain; charset="UTF-8" Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Mon, Aug 19, 2019 at 2:47 PM Nikita Leshenko wrote: > > Before this commit, userspace could disable the GUEST_ACTIVITY_HLT bit in > VMX_MISC yet KVM would happily accept GUEST_ACTIVITY_HLT activity state in > VMCS12. We can fix it by either failing VM entries with HLT activity state when > it's not supported or by disallowing clearing this bit. > > The latter is preferable. If we go with the former, to disable > GUEST_ACTIVITY_HLT userspace also has to make CPU_BASED_HLT_EXITING a "must be > 1" control, otherwise KVM will be presenting a bogus model to L1. > > Don't fail writes that disable GUEST_ACTIVITY_HLT to maintain backwards > compatibility. > > Reviewed-by: Liran Alon > Reviewed-by: Krish Sadhukhan > Signed-off-by: Nikita Leshenko > --- > arch/x86/kvm/vmx/nested.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c > index 46af3a5e9209..24734946ec75 100644 > --- a/arch/x86/kvm/vmx/nested.c > +++ b/arch/x86/kvm/vmx/nested.c > @@ -1102,6 +1102,14 @@ static int vmx_restore_vmx_misc(struct vcpu_vmx *vmx, u64 data) > if (vmx_misc_mseg_revid(data) != vmx_misc_mseg_revid(vmx_misc)) > return -EINVAL; > > + /* > + * We always support HLT activity state. In the past it was possible to > + * turn HLT bit off (without actually turning off HLT activity state > + * support) so we don't fail vmx_restore_vmx_misc if this bit is turned > + * off. > + */ > + data |= VMX_MISC_ACTIVITY_HLT; > + > vmx->nested.msrs.misc_low = data; > vmx->nested.msrs.misc_high = data >> 32; > This change breaks live migration to an upgraded kernel, since it doesn't allow the IA32_VMX_MISC MSR to be restored to its original value. I think this warrants a quirk.