From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757294AbcIUPWW (ORCPT ); Wed, 21 Sep 2016 11:22:22 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59836 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755812AbcIUPWU (ORCPT ); Wed, 21 Sep 2016 11:22:20 -0400 Subject: Re: [PATCH 2/6] kvm: x86: drop read_tsc_offset() To: Jim Mattson References: <1474036056-21270-1-git-send-email-lcapitulino@redhat.com> <1474036056-21270-3-git-send-email-lcapitulino@redhat.com> <41e7b724-07dd-9c9d-3119-c12e50adbe44@redhat.com> Cc: Luiz Capitulino , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , rostedt@goodmis.org, mhiramat@kernel.org, mtosatti@redhat.com From: Paolo Bonzini Message-ID: <6d755392-d0f7-078f-8db2-b6539846d709@redhat.com> Date: Wed, 21 Sep 2016 17:22:14 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Wed, 21 Sep 2016 15:22:19 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 21/09/2016 17:19, Jim Mattson wrote: > Doesn't that assume you can run the merge program in L1? You only need the TSC offset, but we should make sure that L0 tracepoints contain enough information to figure out the L0->L2 TSC offsets (they are the values in VMCS02). That said, how would you get the trace from L1 if you don't have access to it? Paolo > On Mon, Sep 19, 2016 at 10:37 PM, Paolo Bonzini wrote: >> >> >> On 20/09/2016 00:18, Jim Mattson wrote: >>> Hmmm. Yes, I think it does. With this patch series, >>> vcpu->arch.tsc_offset appears to contain L1's TSC offset (perhaps >>> making vmx->nested.vmcs01_tsc_offset redundant). >>> >>> However, this unfortunately limits the newly added functionality to >>> merging host and *L1* guest traces. It doesn't work with L2 (or >>> deeper) guests. Or perhaps I'm missing something? >> >> You can merge L1/L2 first and then host/L1. >> >> Paolo