Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760902Ab3GSR5J (ORCPT ); Fri, 19 Jul 2013 13:57:09 -0400 Received: from g5t0007.atlanta.hp.com ([15.192.0.44]:1131 "EHLO g5t0007.atlanta.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759986Ab3GSR5H (ORCPT ); Fri, 19 Jul 2013 13:57:07 -0400 Message-ID: <1374256575.24916.176.camel@misato.fc.hp.com> Subject: Re: [PATCH] mm/hotplug, x86: Disable ARCH_MEMORY_PROBE by default From: Toshi Kani To: KOSAKI Motohiro Cc: Andrew Morton , "linux-mm@kvack.org" , LKML , x86@kernel.org, Yasuaki Ishimatsu , Tang Chen , "vasilis.liaskovitis" Date: Fri, 19 Jul 2013 11:56:15 -0600 In-Reply-To: References: <1374097503-25515-1-git-send-email-toshi.kani@hp.com> <1374103783.24916.49.camel@misato.fc.hp.com> <1374105078.24916.62.camel@misato.fc.hp.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.6.4 (3.6.4-3.fc18) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2704 Lines: 54 On Wed, 2013-07-17 at 20:24 -0400, KOSAKI Motohiro wrote: > On Wed, Jul 17, 2013 at 7:51 PM, Toshi Kani wrote: > > On Wed, 2013-07-17 at 19:33 -0400, KOSAKI Motohiro wrote: > >> On Wed, Jul 17, 2013 at 7:29 PM, Toshi Kani wrote: > >> > On Wed, 2013-07-17 at 19:22 -0400, KOSAKI Motohiro wrote: > >> >> On Wed, Jul 17, 2013 at 5:45 PM, Toshi Kani wrote: > >> >> > CONFIG_ARCH_MEMORY_PROBE enables /sys/devices/system/memory/probe > >> >> > interface, which allows a given memory address to be hot-added as > >> >> > follows. (See Documentation/memory-hotplug.txt for more detail.) > >> >> > > >> >> > # echo start_address_of_new_memory > /sys/devices/system/memory/probe > >> >> > > >> >> > This probe interface is required on powerpc. On x86, however, ACPI > >> >> > notifies a memory hotplug event to the kernel, which performs its > >> >> > hotplug operation as the result. Therefore, users should not be > >> >> > required to use this interface on x86. This probe interface is also > >> >> > error-prone that the kernel blindly adds a given memory address > >> >> > without checking if the memory is present on the system; no probing > >> >> > is done despite of its name. The kernel crashes when a user requests > >> >> > to online a memory block that is not present on the system. > >> >> > > >> >> > This patch disables CONFIG_ARCH_MEMORY_PROBE by default on x86, > >> >> > and clarifies it in Documentation/memory-hotplug.txt. > >> >> > >> >> Why don't you completely remove it? Who should use this strange interface? > >> > > >> > According to the comment below, this probe interface is used on powerpc. > >> > So, we cannot remove it, but to disable it on x86. > >> > >> I meant x86. Why can't we completely remove ARCH_MEMORY_PROBE section > >> from x86 Kconfig? > > > > Oh, I see what you meant. I do not expect any need for end-users, but I > > was not sure if someone working on the memory hotplug development might > > use it for fake hot-add testing. Yes, if you folks do not see any need, > > I will remove it from x86 Kconfig. > > Then it's ok to submit your patch now. > > Acked-by: KOSAKI Motohiro I just sent v2 patch, but did not put your Ack since I did not remove the option from x86 Kconfig per discussions with Dave. I'd really appreciate if you can take a look at the v2 and re-ack it if it still makes sense to you. Thanks, -Toshi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/