linux-kernel - Re: [PATCH 2/2] x86, e820 disable ACPI Memory Hotplug if memory mapping is specified by user [v2]

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20140114015202.GD4327@dhcp-16-126.nay.redhat.com>
Date:	Tue, 14 Jan 2014 09:52:02 +0800
From:	Dave Young <dyoung@...hat.com>
To:	Toshi Kani <toshi.kani@...com>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Prarit Bhargava <prarit@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	Bodo Eggert <7eggert@....de>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	the arch/x86 maintainers <x86@...nel.org>,
	Len Brown <lenb@...nel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Linn Crosetto <linn@...com>, Pekka Enberg <penberg@...nel.org>,
	Yinghai Lu <yinghai@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tang Chen <tangchen@...fujitsu.com>,
	Wen Congyang <wency@...fujitsu.com>,
	Vivek Goyal <vgoyal@...hat.com>, linux-acpi@...r.kernel.org,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH 2/2] x86, e820 disable ACPI Memory Hotplug if memory
 mapping is specified by user [v2]

On 01/13/14 at 06:09pm, Toshi Kani wrote:
> On Mon, 2014-01-13 at 16:53 -0800, H. Peter Anvin wrote:
> > On 01/13/2014 04:33 PM, Toshi Kani wrote:
> > > 
> > > I do not think it makes sense.  You needed memmap=exactmap as a
> > > workaround because the kernel did not boot with the firmware's memory
> > > info.  So, it's broken, and you requested the kernel to ignore the
> > > firmware info.
> > > 
> > > Why do you think memory hotplug needs to be supported under such
> > > condition, which has to use the broken firmware info?
> > > 
> > 
> > Even more than memory hotplug: what do we do with NUMA?  Since we have
> > already told the kernel "the firmware is bogus" it would seem that any
> > NUMA optimizations would be a bit ... cantankerous at best, no?
> 
> Agreed that NUMA info can be bogus in this case, but is probably not
> critical.
> 
> In majority of the cases, memmap=exactmap is used for kdump and the
> firmware info is sane.  So, I think we should keep NUMA enabled since it
> could be useful when multiple CPUs are enabled for kdump.

In Fedora kdump, we by default add numa=off to 2nd kernel cmdline because
enabling numa will use a lot more memory, at the same time we have only 128M
reserved by default..

Thanks
Dave
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/