linux-kernel - Re: [PATCH] x86: Fix adjust_range_size

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Message-ID: <CAE9FiQXrG0qZ3yJzxsOWhVtzxEY6R9g=sL7EHXZZKNj=BTjmxg@mail.gmail.com>
Date:	Tue, 28 May 2013 16:43:44 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	Yuanhan Liu <yuanhan.liu@...ux.intel.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: Fix adjust_range_size_mask calling position

On Tue, May 28, 2013 at 4:36 PM, H. Peter Anvin <hpa@...or.com> wrote:
> On 05/28/2013 04:28 PM, Yinghai Lu wrote:
>>
>> Actually there is bug about calling sequence for
>> adjust_range_page_size_mask(). Merge first will make
>> adjust to 1g for second partial 1g range fail.
>>
>
> Sorry, I'm not sure I understand what the above paragraph is trying to say.

We merge the continuous range with same page size allow too early.
in the case
     [mem 0x00200000-0x3fffffff] page 2M
     [mem 0x40000000-0x7bffffff] page 2M
after merging them, will get
     [mem 0x00200000-0x7bffffff] page 2M
even we can use 1G page to map
     [mem 0x40000000-0x7bffffff]

that will cause problem, because we map
     [mem 0x7fe00000-0x7fffffff] page 1G
     [mem 0x7c000000-0x7fdfffff] page 1G
with 1G page.

so need to adjust page size at first before merge
     [mem 0x00200000-0x3fffffff] page 2M
     [mem 0x40000000-0x7bffffff] page 2M

Yinghai
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