Subject: Re: dom0 panic with Upstream Linux 4.1 tree
To: zhenzhong.duan@oracle.com, LKML <linux-kernel@vger.kernel.org>
References: <55D18E10.4010903@oracle.com>
From: =?UTF-8?Q?Juergen_Gro=c3=9f?= <jgross@suse.com>
Message-ID: <55DB55B4.7090107@suse.com>
Date: Mon, 24 Aug 2015 19:34:44 +0200
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On 08/17/2015 09:32 AM, Zhenzhong Duan wrote:
> Hi Maintainers
>
> I found below panic when bootup OVM3.3.3 on HP PROLIANT DL980 G7 with
> dom0_mem=max:128G, not reproduce with dom0_mem=max:127G.
> Dom0 kernel is uek4 4.1.5-5.el6uek which is based on Upstream Linux 4.1
> tree. This looks like an upstream issue.
> Appereciate any patch/fix. Thanks

I don't think there is an easy patch in 4.1 to fix that. Your system has
half of the physical memory above the 512GB boundary making it
impossible for dom0 to use. Dom0 tries to use the memory layout of the
physical host, so it can only use memory below 512GB.

As you try to allocate 128GB for Dom0 some of the memory will end above
the magic boundary (there is only a little bit less than 128GB below
the boundary available).

For 4.3 I have posted a patch series which will eventually make it into
the kernel allowing Dom0 (and other pv-domains as well) to use memory
above the 512GB boundary.


Juergen
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