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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 DA7F1C433DB for ; Mon, 15 Mar 2021 22:40:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 80EB664F52 for ; Mon, 15 Mar 2021 22:40:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232066AbhCOWkC convert rfc822-to-8bit (ORCPT ); Mon, 15 Mar 2021 18:40:02 -0400 Received: from ex13-edg-ou-001.vmware.com ([208.91.0.189]:1445 "EHLO EX13-EDG-OU-001.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231377AbhCOWjp (ORCPT ); Mon, 15 Mar 2021 18:39:45 -0400 X-Greylist: delayed 901 seconds by postgrey-1.27 at vger.kernel.org; Mon, 15 Mar 2021 18:39:45 EDT Received: from sc9-mailhost3.vmware.com (10.113.161.73) by EX13-EDG-OU-001.vmware.com (10.113.208.155) with Microsoft SMTP Server id 15.0.1156.6; Mon, 15 Mar 2021 15:24:43 -0700 Received: from [10.200.196.160] (unknown [10.200.196.160]) by sc9-mailhost3.vmware.com (Postfix) with ESMTP id 323722050D; Mon, 15 Mar 2021 15:24:44 -0700 (PDT) Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 (Mac OS X Mail 14.0 \(3654.60.0.2.21\)) Subject: Re: [PATCH] x86/vmware: avoid TSC recalibration From: Alexey Makhalov In-Reply-To: <87im8bildr.fsf@vitty.brq.redhat.com> Date: Mon, 15 Mar 2021 15:24:43 -0700 CC: , , "H . Peter Anvin" , Borislav Petkov , , , , Content-Transfer-Encoding: 8BIT Message-ID: <84F586C5-EECE-4EE5-8988-64D8E0325D7A@vmware.com> References: <20210105004752.131069-1-amakhalov@vmware.com> <87im8bildr.fsf@vitty.brq.redhat.com> To: Vitaly Kuznetsov X-Mailer: Apple Mail (2.3654.60.0.2.21) Received-SPF: None (EX13-EDG-OU-001.vmware.com: amakhalov@vmware.com does not designate permitted sender hosts) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Vitaly, I believe, it is responsibility of each guest code to set X86_FEATURE_TSC_KNOWN_FREQ cap. Regarding VMware guest, there is a case where vmware_tsc_khz is zero (not provided by hypervisor) and TSC frequency should be calculated. Sorry for late response. Regards, —Alexey > On Jan 5, 2021, at 5:06 AM, Vitaly Kuznetsov wrote: > > Alexey Makhalov writes: > >> When TSC frequency is known (retrieved from hypervisor), we should skip >> TSC refined calibration by setting X86_FEATURE_TSC_KNOWN_FREQ. >> >> Signed-off-by: Alexey Makhalov >> --- >> arch/x86/kernel/cpu/vmware.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c >> index c6ede3b3d302..83164110ccc5 100644 >> --- a/arch/x86/kernel/cpu/vmware.c >> +++ b/arch/x86/kernel/cpu/vmware.c >> @@ -378,6 +378,8 @@ static void __init vmware_set_capabilities(void) >> { >> setup_force_cpu_cap(X86_FEATURE_CONSTANT_TSC); >> setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE); >> + if (vmware_tsc_khz) >> + setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); >> if (vmware_hypercall_mode == CPUID_VMWARE_FEATURES_ECX_VMCALL) >> setup_force_cpu_cap(X86_FEATURE_VMCALL); >> else if (vmware_hypercall_mode == CPUID_VMWARE_FEATURES_ECX_VMMCALL) > > The same trick is being used in Xen/Jailhouse/KVM code already and > Hyper-V overwrites x86_platform.calibrate_tsc/x86_platform.calibrate_cpu > hooks to basically achive the same goal. Should we maybe introduce a > flag in 'struct hypervisor_x86' or something like that to unify all > this? > > Just a suggestion. > > -- > Vitaly