From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl1-f198.google.com (mail-pl1-f198.google.com [209.85.214.198]) by kanga.kvack.org (Postfix) with ESMTP id CB9B16B0003 for ; Thu, 1 Nov 2018 11:39:18 -0400 (EDT) Received: by mail-pl1-f198.google.com with SMTP id 33-v6so11398320pld.19 for ; Thu, 01 Nov 2018 08:39:18 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id d16-v6si31063696pfj.251.2018.11.01.08.39.17 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 01 Nov 2018 08:39:17 -0700 (PDT) Subject: Re: [PATCH] x86/build: Build VSMP support only if selected References: <20181030230905.xHZmM%akpm@linux-foundation.org> <9e14d183-55a4-8299-7a18-0404e50bf004@infradead.org> <054cd800-5124-f897-0069-aba49f8eb654@suse.com> <3c75860d-e3d7-8c28-6120-f6056200f941@scalemp.com> From: Juergen Gross Message-ID: <0d472636-e39d-8cd3-4a47-2b9dc139b7fe@suse.com> Date: Thu, 1 Nov 2018 16:39:13 +0100 MIME-Version: 1.0 In-Reply-To: <3c75860d-e3d7-8c28-6120-f6056200f941@scalemp.com> Content-Type: text/plain; charset=windows-1252 Content-Language: de-DE Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Eial Czerwacki Cc: Thomas Gleixner , Randy Dunlap , "Shai Fultheim (Shai@ScaleMP.com)" , Andrew Morton , "broonie@kernel.org" , "mhocko@suse.cz" , Stephen Rothwell , "linux-next@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , LKML , "mm-commits@vger.kernel.org" , X86 ML , 'Oren Twaig' On 01/11/2018 16:09, Eial Czerwacki wrote: > Greetings, > > On 11/01/2018 03:45 PM, Juergen Gross wrote: >> On 01/11/2018 14:10, Eial Czerwacki wrote: >>> Greetings, >>> >>> On 11/01/2018 12:39 PM, Shai Fultheim (Shai@ScaleMP.com) wrote: >>>> On 01/11/18 11:37, Thomas Gleixner wrote: >>>> >>>>> VSMP support is built even if CONFIG_X86_VSMP is not set. This leads to a build >>>>> breakage when CONFIG_PCI is disabled as well. >>>>> >>>>> Build VSMP code only when selected. >>>> >>>> This patch disables detect_vsmp_box() on systems without CONFIG_X86_VSMP, due to >>>> the recent 6da63eb241a05b0e676d68975e793c0521387141. This is significant >>>> regression that will affect significant number of deployments. >>>> >>>> We will reply shortly with an updated patch that fix the dependency on pv_irq_ops, >>>> and revert to CONFIG_PARAVIRT, with proper protection for CONFIG_PCI. >>>> >>> >>> here is the proper patch which fixes the issue on hand: >>> From ebff534f8cfa55d7c3ab798c44abe879f3fbe2b8 Mon Sep 17 00:00:00 2001 >>> From: Eial Czerwacki >>> Date: Thu, 1 Nov 2018 15:08:32 +0200 >>> Subject: [PATCH] x86/build: Build VSMP support only if CONFIG_PCI is >>> selected >>> >>> vsmp dependency of pv_irq_ops removed some years ago, so now let's clean >>> it up from vsmp_64.c. >>> >>> In short, "cap & ctl & (1 << 4)" was always returning 0, as such we can >>> remove all the PARAVIRT/PARAVIRT_XXL code handling that. >>> >>> However, the rest of the code depends on CONFIG_PCI, so fix it accordingly. >>> >>> Signed-off-by: Eial Czerwacki >>> Acked-by: Shai Fultheim >>> --- >>> arch/x86/Kconfig | 1 - >>> arch/x86/kernel/vsmp_64.c | 80 >>> +++-------------------------------------------- >>> 2 files changed, 5 insertions(+), 76 deletions(-) >>> >>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig >>> index c51c989..4b187ca 100644 >>> --- a/arch/x86/Kconfig >>> +++ b/arch/x86/Kconfig >>> @@ -524,7 +524,6 @@ config X86_VSMP >>> bool "ScaleMP vSMP" >>> select HYPERVISOR_GUEST >>> select PARAVIRT >> >> Do you really still need PARAVIRT and HYPERVISOR_GUEST? >> Maybe you want IRQ_REMAP instead? >> > Better performance is achieved with PARAVIRTed kernel. Hence we keep > them both in. Do you have an explanation for that? Normally PARAVIRT is expected to have a small negative impact on performance. Juergen