linux-kernel - Re: [PATCH] x86/numa: kernel stack corruption fix

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Message-ID: <20150403070347.GB22579@dhcp-128-53.nay.redhat.com>
Date:	Fri, 3 Apr 2015 15:03:47 +0800
From:	Dave Young <dyoung@...hat.com>
To:	Yasuaki Ishimatsu <yasu.isimatu@...il.com>
Cc:	Xishi Qiu <qiuxishi@...wei.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, tglx@...utronix.de, bhe@...hat.com,
	mingo@...hat.com, hpa@...or.com, akpm@...ux-foundation.org
Subject: Re: [PATCH] x86/numa: kernel stack corruption fix

> > > >>
> > > >> The above reserved region includes 0x40004000, a page excluded in
> > > >> trim_snb_memory. For this memblock reserved region the nid is not set it is
> > > >> still default value MAX_NUMNODES. later node_set callback will set bit
> > > >> MAX_NUMNODES in nodemask bitmap thus stack corruption happen. 
> > > >>
> > > 
> > > Hi Dave,
> > > 
> > > Is it means, first reserved region 0x40000000 - 0x40100000, then boot the kdump
> > > kernel, so this region is not include in "numa_meminfo", and memblock.reserved
> > > (0x40004000) is still MAX_NUMNODES from trim_snb_memory().
> > 
> > Right, btw, I booted kdump kernel with numa=off for saving memory.
> > 
> > I suspect it will also be reproduced with mem=XYZ with normal kernel.
> 
> Does the issue occur on your system with mem=0x40000000?
> 
> I think the issue occurs when reserved memory range is not includes
> in system ram which informed by e820 or SRAT table. On your system,
> 0x40004000 is reserved by trim_snb_memory(). But if you use mem=0x40000000,
> the system ram is limited within 0x40000000. So the issue will occur.

It does occur with mem=800M during my previous test, I think it will occur with
mem=0x40000000 as well though I did not test mem=0x40000000.

Thanks
Dave
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