linux-kernel - Re: [PATCH 26/46] x86, mm, Xen: Remove mapping_pagetable

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Message-ID: <CAE9FiQUc0Jz0g+oZXye95dNCV0W4YMr-WMroUR_HaUmh-qZwoA@mail.gmail.com>
Date:	Tue, 13 Nov 2012 10:51:59 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>, Jacob Shin <jacob.shin@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 26/46] x86, mm, Xen: Remove mapping_pagetable_reserve()

On Tue, Nov 13, 2012 at 8:36 AM, Stefano Stabellini
<stefano.stabellini@...citrix.com> wrote:
> On Mon, 12 Nov 2012, Yinghai Lu wrote:
>> Page table area are pre-mapped now after
>>       x86, mm: setup page table in top-down
>>       x86, mm: Remove early_memremap workaround for page table accessing on 64bit
>>
>> mapping_pagetable_reserve is not used anymore, so remove it.
>
> You should mention in the description of the patch that you are
> removing mask_rw_pte too.
>
> The reason why you can do that safely is that you previously modified
> allow_low_page to always return pages that are already mapped, moreover
> xen_alloc_pte_init, xen_alloc_pmd_init, etc, will mark the page RO
> before hooking it into the pagetable automatically.

updated change log:
---
x86, mm, Xen: Remove mapping_pagetable_reserve()

Page table area are pre-mapped now after
        x86, mm: setup page table in top-down
        x86, mm: Remove early_memremap workaround for page table
accessing on 64bit

mapping_pagetable_reserve is not used anymore, so remove it.

Also remove operation in mask_rw_pte(), as modified allow_low_page
always return pages that are already mapped, moreover
xen_alloc_pte_init, xen_alloc_pmd_init, etc, will mark the page RO
before hooking it into the pagetable automatically.

-v2: add changelog about mask_rw_pte() from Stefano.
-----


>
> [ ... ]
>
> you should just get rid of mask_rw_pte completely

then how about 32bit mask_rw_pte? Maybe you can clean up that later?

Thanks

Yinghai
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