linux-kernel - Re: srat: harsh hot-pluggable memory check?

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Message-ID: <20130111202501.GL30577@one.firstfloor.org>
Date:	Fri, 11 Jan 2013 21:25:01 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Davidlohr Bueso <davidlohr.bueso@...com>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-acpi@...r.kernel.org,
	zeus@....org, linux-kernel@...r.kernel.org
Subject: Re: srat: harsh hot-pluggable memory check?

On Fri, Jan 11, 2013 at 12:13:50PM -0800, Davidlohr Bueso wrote:
> On Thu, 2013-01-10 at 21:02 +0100, Andi Kleen wrote:
> > > This only mentions that the system supports hot-plugging, and IMHO if the
> > > user decides not to use CONFIG_MEMORY_HOTPLUG, it shouldn't be considered an error.
> > > Therefore would it be ok to drop the check? Or am I missing something?
> > 
> > The very strict checks were originally implemented because various early
> > BIOS had largely fictional SRATs, and trusting them blindly caused
> > boot failures or a lot of wasted memory for unnecessary hotplug zones. 
> > The wasted memory was mainly a problem with the old memory hotplug
> > implementation that pre-allocated memmaps, that's not a problem anymore.
> > However there may be still some other failure cases.
> > 
> 
> Would you be willing to take a patch that drops this check then? Or do
> you see any other scenario where it would still be valid?

I don't maintain this code. 

Personally I would be vary to any changes in this area, unless you
can very clearly demonstrate that the change cannot break any old
system.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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