From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755872AbcGFV1X (ORCPT ); Wed, 6 Jul 2016 17:27:23 -0400 Received: from mail-wm0-f53.google.com ([74.125.82.53]:38772 "EHLO mail-wm0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755769AbcGFV1V (ORCPT ); Wed, 6 Jul 2016 17:27:21 -0400 Subject: Re: kvm: RDTSCP on AMD To: Eduardo Habkost References: <20160706124438.GB7300@pd.tnic> <20160706173440.GU4131@thinpad.lan.raisama.net> Cc: Borislav Petkov , =?UTF-8?B?SsO2cmcgUsO2ZGVs?= , Andre Przywara , kvm ML , lkml From: Paolo Bonzini Message-ID: <0b830bbe-182a-3bd3-bab0-0c2fd823edd4@redhat.com> Date: Wed, 6 Jul 2016 23:27:16 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1 MIME-Version: 1.0 In-Reply-To: <20160706173440.GU4131@thinpad.lan.raisama.net> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/07/2016 19:34, Eduardo Habkost wrote: >> > Nothing is needed in the kernel actually. You can skip the intercept >> > by running the guest with MSR_TSC_AUX set to the guest's expected value. >> > Which KVM does, except that it's botched so I need to apply the >> > patch in https://lkml.org/lkml/2016/4/13/802. > Do you mean -cpu Opteron_G*,+rdtscp will be buggy on Linux v4.5? > (v4.5 reports rdtscp as supported in GET_SUPPORTED_CPUID) > > Can we do something to make QEMU detect the buggy kernel before > allowing rdtscp to be enabled, or should we just tell people to > upgrade their kernel? We usually just tell people to use the latest stable kernel. Adding new CPU models is not a big deal, in fact it's almost easier than getting compat properties right. :) Paolo