Subject: Re: [PATCH v2] Call xen_cleanhighmap() with 4MB aligned for page
 tables mapping
To: Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Zhenzhong Duan <zhenzhong.duan@oracle.com>, mingo@redhat.com,
        tglx@linutronix.de, hpa@zytor.com
Cc: x86@kernel.org, xen-devel@lists.xenproject.org,
        srinivas.eeda@oracle.com, joe.jin@oracle.com,
        linux-kernel@vger.kernel.org
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 <44ebc914-d1a3-06ac-9ec5-b866d5f04e0a@oracle.com>
From: Juergen Gross <jgross@suse.com>
Message-ID: <9faf8d7b-227f-2ecd-26e6-44ae4270d469@suse.com>
Date: Wed, 27 Sep 2017 16:33:04 +0200
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On 27/09/17 15:38, Boris Ostrovsky wrote:
> On 09/27/2017 05:43 AM, Juergen Gross wrote:
>> On 27/09/17 11:41, Zhenzhong Duan wrote:
>>> When bootup a PVM guest with large memory(Ex.240GB), XEN provided initial
>>> mapping overlaps with kernel module virtual space. When mapping in this space
>>> is cleared by xen_cleanhighmap(), in certain case there could be an 2MB mapping
>>> left. This is due to XEN initialize 4MB aligned mapping but xen_cleanhighmap()
>>> finish at 2MB boundary.
> 
> Does this mapping need to be 4MB-aligned?

I guess you are questioning the alignment of addr to be 4MB?
In this case you are right: the end of the mapping is 4MB aligned, as
correctly stated in the comment added.

> (I also think this should go to stable trees)

Indeed.


Juergen