linux-kernel - Re: [PATCH v2] Call xen_cleanhighmap() with 4MB aligned for page tables mapping

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Date:   Wed, 27 Sep 2017 16:33:04 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Zhenzhong Duan <zhenzhong.duan@...cle.com>, mingo@...hat.com,
        tglx@...utronix.de, hpa@...or.com
Cc:     x86@...nel.org, xen-devel@...ts.xenproject.org,
        srinivas.eeda@...cle.com, joe.jin@...cle.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] Call xen_cleanhighmap() with 4MB aligned for page
 tables mapping

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