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=-5.4 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT 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 B15BDC04EB8 for ; Mon, 10 Dec 2018 20:08:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7B26C2082F for ; Mon, 10 Dec 2018 20:08:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7B26C2082F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729788AbeLJUIq (ORCPT ); Mon, 10 Dec 2018 15:08:46 -0500 Received: from mx1.redhat.com ([209.132.183.28]:40288 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727146AbeLJUIq (ORCPT ); Mon, 10 Dec 2018 15:08:46 -0500 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 97229811DC; Mon, 10 Dec 2018 20:08:45 +0000 (UTC) Received: from localhost (ovpn-116-63.gru2.redhat.com [10.97.116.63]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1B5D060BF1; Mon, 10 Dec 2018 20:08:44 +0000 (UTC) Date: Mon, 10 Dec 2018 18:08:43 -0200 From: Eduardo Habkost To: Borislav Petkov Cc: Paolo Bonzini , =?iso-8859-1?Q?J=F6rg_R=F6del?= , Andre Przywara , kvm ML , lkml , Tom Lendacky , "Daniel P. Berrange" , Eric Blake Subject: Re: kvm: RDTSCP on AMD Message-ID: <20181210200843.GN4669@habkost.net> References: <20181210181328.GA762@zn.tnic> <20181210183730.GJ4669@habkost.net> <20181210184153.GB5482@zn.tnic> <20181210190600.GK4669@habkost.net> <20181210194258.GD5482@zn.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181210194258.GD5482@zn.tnic> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Mon, 10 Dec 2018 20:08:45 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 10, 2018 at 08:42:58PM +0100, Borislav Petkov wrote: > On Mon, Dec 10, 2018 at 05:06:00PM -0200, Eduardo Habkost wrote: > > I mean documenting it. We already have code that will print > > warnings if a feature isn't available. > > > > See my previous attempt to document the minimum kernel version > > at . > > Something like this? > > I still have no clue how to add RDTSCP on pc-*-4.0 and newer. qemu.git master have no PC_COMPAT_3_1 and pc-*-4.0 machine-types yet. I've sent another reply with additional pointers. > > Thx. > > --- > diff --git a/qemu-doc.texi b/qemu-doc.texi > index f7ad1dfe4b69..913b2ef68d54 100644 > --- a/qemu-doc.texi > +++ b/qemu-doc.texi > @@ -37,6 +37,7 @@ > * QEMU System emulator for non PC targets:: > * QEMU Guest Agent:: > * QEMU User space emulator:: > +* System requirements:: > * Implementation notes:: > * Deprecated features:: > * Supported build platforms:: > @@ -2813,6 +2814,13 @@ Act as if the host page size was 'pagesize' bytes > Run the emulation in single step mode. > @end table > > +@node System requirements > +@chapter System requirements > + > +@section KVM kernel module > + > +On x86_64 hosts, the default set of CPU features enabled by the KVM accelerator > +require the host to be running Linux v4.5 or newer. > Sounds good, but it would be nice to document what exactly makes Linux 4.5+ necessary. e.g.: | On x86_64 hosts, it is recommended to run Linux 4.5 or newer on | the host when using the KVM accelerator. | | The Opteron_G2, OpteronG3, Opteron_G4, and Opteron_G5 CPU | models require KVM support for RDTSCP, which was added on | Linux 4.5. I'm CCing some people who may help review English grammar and style. -- Eduardo