From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752138AbdGWNmG (ORCPT ); Sun, 23 Jul 2017 09:42:06 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53904 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751365AbdGWNmE (ORCPT ); Sun, 23 Jul 2017 09:42:04 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 287493680B Authentication-Results: ext-mx06.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx06.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=pbonzini@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 287493680B Subject: Re: [PATCH 6/8] x86: add MULTIUSER dependency for KVM To: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Arnd Bergmann Cc: the arch/x86 maintainers , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Linux Kernel Mailing List , Alex Williamson , kvm@vger.kernel.org References: <20170719125310.2487451-1-arnd@arndb.de> <20170719125310.2487451-7-arnd@arndb.de> <20170719141153.GA17303@potion> <20170719161328.GB17303@potion> From: Paolo Bonzini Message-ID: <8ee0dbeb-9a74-1e9a-2500-978f415c8b40@redhat.com> Date: Sun, 23 Jul 2017 15:41:58 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170719161328.GB17303@potion> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Sun, 23 Jul 2017 13:42:04 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19/07/2017 18:13, Radim Krčmář wrote: > Good point, 'select' seems misused here. > > There is no reason to depend on TASKSTATS (nor NET+MULTIUSER), we only > suggest to enable it with KVM. KVM uses sched_info_on() to handle any > any possible resulting configuration, c9aaa8957f20 ("KVM: Steal time > implementation"). > > KVM would work as intended if 'select' would not enable the option if > its dependencies failed (instead of unconditionally forcing the option). > > Is the preferred way to encode it: > > 'default y if KVM' in config TASK_DELAY_ACCT > (that adds a non-local and enigmatic dependency and also needlessly > expands the possible configuration space) > > or > > 'select TASKSTATS if NET && MULTIUSER' in config KVM > (that is going to break when dependencies of TASKSTATS change again) > > ? I think the former is the closest to what the user actually wants, and it would let us clean up arch/x86/kvm/Kconfig. However it should be "default y if KVM && X86'. Maybe there is room for a new operator "suggest Y" which, when added inside "config X", operates as if "config Y" had a "default y if X". In this case, kvm could do - depends on NET && MULTIUSER - select TASKSTATS + suggest TASKSTATS Thanks, Paolo