linux-kernel - Re: "x86-64, mm: Put early page table high" causes crash on Xen

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Date:	Tue, 8 Mar 2011 08:39:03 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Jeremy Fitzhardinge <Jeremy.Fitzhardinge@...rix.com>
Subject: Re: "x86-64, mm: Put early page table high" causes crash on Xen

On Tue, Mar 8, 2011 at 4:14 AM, Stefano Stabellini
<stefano.stabellini@...citrix.com> wrote:
>> > [    0.000000] DEBUG alloc low page(cf965000, 00001000)
>>
>> these are not mapped yet, and need to use early_ioremap.
>
> In fact we are mapping them inside alloc_low_page. No need for
> map_low_page, right?

alloc_low_page return virtual address, but it can not be used to
access that position right away.
so in that case map_low_page is used to convert that virtual address
to phy address and then to early map address.

Yinghai
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