From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Fitzhardinge Subject: Re: [patch 08/18] x86: pvclock: generic pvclock vsyscall initialization Date: Mon, 29 Oct 2012 10:46:35 -0700 Message-ID: <508EC0FB.3050401@goop.org> References: <20121024131340.742340256@redhat.com> <20121024131621.658249278@redhat.com> <508E902C.4080402@parallels.com> <20121029145419.GB13104@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Glauber Costa , kvm@vger.kernel.org, johnstul@us.ibm.com, zamsden@gmail.com, gleb@redhat.com, avi@redhat.com, pbonzini@redhat.com To: Marcelo Tosatti Return-path: Received: from claw.goop.org ([74.207.240.146]:34892 "EHLO claw.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755165Ab2J2R4e (ORCPT ); Mon, 29 Oct 2012 13:56:34 -0400 In-Reply-To: <20121029145419.GB13104@amt.cnet> Sender: kvm-owner@vger.kernel.org List-ID: On 10/29/2012 07:54 AM, Marcelo Tosatti wrote: > On Mon, Oct 29, 2012 at 06:18:20PM +0400, Glauber Costa wrote: >> On 10/24/2012 05:13 PM, Marcelo Tosatti wrote: >>> Index: vsyscall/arch/x86/Kconfig >>> =================================================================== >>> --- vsyscall.orig/arch/x86/Kconfig >>> +++ vsyscall/arch/x86/Kconfig >>> @@ -632,6 +632,13 @@ config PARAVIRT_SPINLOCKS >>> >>> config PARAVIRT_CLOCK >>> bool >>> +config PARAVIRT_CLOCK_VSYSCALL >>> + bool "Paravirt clock vsyscall support" >>> + depends on PARAVIRT_CLOCK && GENERIC_TIME_VSYSCALL >>> + ---help--- >>> + Enable performance critical clock related system calls to >>> + be executed in userspace, provided that the hypervisor >>> + supports it. >>> >>> endif >> Besides debugging, what is the point in having this as an >> extra-selectable? Is there any case in which a virtual machine has code >> for this, but may decide to run without it ? > Don't think so (its pretty small anyway, the code). > >> I believe all this code in vsyscall should be wrapped in PARAVIRT_CLOCK >> only. > Unless Jeremy has a reason, i'm fine with that. I often set up blind config variables for dependency management; I'm guessing the "GENERIC_TIME_VSYSCALL" dependency is important. I think the problem is that this exists, but that it's a user-selectable option. Removing the prompt should fix that. J