From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Hildenbrand Subject: Re: PATCH: setup_vmcs_config: disable TSC scaling on unlike processors Date: Tue, 6 Dec 2016 09:49:16 +0100 Message-ID: <59a3f1a2-5b9e-2ca7-5285-1469fef40f42@redhat.com> References: <20161202150632.GA22204@potion> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Cc: kvm@vger.kernel.org, pbonzini@redhat.com To: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Don Bowman Return-path: Received: from mx1.redhat.com ([209.132.183.28]:51628 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751396AbcLFItT (ORCPT ); Tue, 6 Dec 2016 03:49:19 -0500 In-Reply-To: <20161202150632.GA22204@potion> Sender: kvm-owner@vger.kernel.org List-ID: Am 02.12.2016 um 16:07 schrieb Radim Krčmář: > Subjects that touch only arch/x86/kvm/vmx.c are usually prefixed with > "[PATCH] KVM: VMX:". > > 2016-12-01 21:32-0500, Don Bowman: >> Add an enable_tsc_scaling parameter to kvm >> >> Signed-off-by: Don Bowman >> --- >> >> My system has what i thought were two identical processors (same >> stepping ID etc). >> However, bafflingly, one of them has the ability to do TSC scaling, >> and one does not (as reported in the vmcs). > > Wow, the chip doesn't sound trustworthy. > >> This in turn causes kvm to give up entirely. >> >> I feel a better solution is to mask off this capability on the one processor. > > I like the global toggle better -- it is less code with more uses. (not having much insight) what speaks against allowing such features only if available on all CPUs symmetrically? I actually prefer having an automatism to some magic toggle. -- David