From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752591AbdK3MZl (ORCPT ); Thu, 30 Nov 2017 07:25:41 -0500 Received: from mx1.redhat.com ([209.132.183.28]:40738 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750723AbdK3MZk (ORCPT ); Thu, 30 Nov 2017 07:25:40 -0500 Subject: Re: [PATCH v3 3/9] KVM: x86: Add Intel Processor Trace virtualization mode To: Luwei Kang , kvm@vger.kernel.org Cc: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, rkrcmar@redhat.com, linux-kernel@vger.kernel.org, joro@8bytes.org, Chao Peng References: <1511814242-12949-1-git-send-email-luwei.kang@intel.com> <1511814242-12949-4-git-send-email-luwei.kang@intel.com> From: Paolo Bonzini Message-ID: <9a15e683-8627-0fc6-a95d-3ac6a0468509@redhat.com> Date: Thu, 30 Nov 2017 13:25:34 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <1511814242-12949-4-git-send-email-luwei.kang@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Thu, 30 Nov 2017 12:25:40 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 27/11/2017 21:23, Luwei Kang wrote: > +/* Default is host guest mode. */ > +static int __read_mostly pt_mode = PT_MODE_HOST_GUEST; > +module_param(pt_mode, int, S_IRUGO); > + This will cause a slowdown on new processors. Please make the default PT_SYSTEM until that is addressed (with a combination of XSAVES, caching the host rtit_ctl at the kernel level, or something like that). Paolo