From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753541AbaGKXb7 (ORCPT ); Fri, 11 Jul 2014 19:31:59 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:27050 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750775AbaGKXb6 (ORCPT ); Fri, 11 Jul 2014 19:31:58 -0400 Message-Id: <201407112331.s6BNVp9C022670@aserz7021.oracle.com> Date: Fri, 11 Jul 2014 19:31:31 -0400 Subject: Re: [PATCH] xen: Introduce 'xen_nopv' to disable PV extensions for HVM guests. From: Konrad Rzeszutek Wilk To: "H. Peter Anvin" Cc: konrad@kernel.org, xen-devel@lists.xenproject.org, boris.ostrovsky@oracle.com, david.vrabel@citrix.com, linux-kernel@vger.kernel.org MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 X-Source-IP: acsinet21.oracle.com [141.146.126.237] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id s6BNWJMs024658 On Jul 11, 2014 7:14 PM, "H. Peter Anvin" wrote: > > On 07/11/2014 04:09 PM, Konrad Rzeszutek Wilk wrote: > > > > On Jul 11, 2014 6:52 PM, "H. Peter Anvin" wrote: > >> > >> On 07/11/2014 12:53 PM, konrad@kernel.org wrote: > >>> > >>> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt > >>> index c1b9aa8..5dcfa6e 100644 > >>> --- a/Documentation/kernel-parameters.txt > >>> +++ b/Documentation/kernel-parameters.txt > >>> @@ -3691,6 +3691,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted. > >>>   Disables the ticketlock slowpath using Xen PV > >>>   optimizations. > >>>   > >>> + xen_nopv [X86,XEN] > >>> + Disables the PV optimizations forcing the guest to run > >>> + as generic HVM guest with no PV drivers. > >>> + > >>>   xirc2ps_cs= [NET,PCMCIA] > >>>   Format: > >>>   ,,,,,[,[,[,]]] > >>> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c > >>> index ffb101e..eb82239 100644 > >>> --- a/arch/x86/xen/enlighten.c > >>> +++ b/arch/x86/xen/enlighten.c > >>> @@ -1826,8 +1826,19 @@ static void __init xen_hvm_guest_init(void) > >>>   xen_hvm_init_mmu_ops(); > >>>   } > >>>   > >>> +static bool xen_nopv = false; > >>> +static __init int xen_parse_nopv(char *arg) > >>> +{ > >>> +       xen_nopv = true; > >>> +       return 0; > >>> +} > >>> +early_param("xen_nopv", xen_parse_nopv); > >>> + > >>>   static uint32_t __init xen_hvm_platform(void) > >>>   { > >>> + if (xen_nopv) > >>> + return 0; > >>> + > >>>   if (xen_pv_domain()) > >>>   return 0; > >>>   > >>> @@ -1836,6 +1847,8 @@ static uint32_t __init xen_hvm_platform(void) > >>>   > >>>   bool xen_hvm_need_lapic(void) > >>>   { > >>> + if (xen_nopv) > >>> + return false; > >>>   if (xen_pv_domain()) > >>>   return false; > >>>   if (!xen_hvm_domain()) > >>> > >> > >> Any reason to not simply let xen_pv_domain() return false here? > > > > It does return false already. > > > > Did you mean to collapse them together? > > OK, I'm confused.  The description of the option makes it look like it > could disable things associated with PV domains, but it looks like it > actually disables things having to do with HVM domains... > Thank you for pointing that out. I will update the documentation to be more clear and specific. It is as you surmised only for HVM guest. The a > -hpa > {.n++%ݶw{.n+{G{ayʇڙ,jfhz_(階ݢj"mG?&~iOzv^m ?I