linux-kernel - Re: [PATCH 6/7] x86, mm: setup page table from top-down

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Message-ID: <50A6746D.8070506@zytor.com>
Date:	Fri, 16 Nov 2012 09:14:21 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, Jacob Shin <jacob.shin@....com>,
	Tejun Heo <tj@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 6/7] x86, mm: setup page table from top-down

On 10/10/2012 10:38 AM, Yinghai Lu wrote:
> On Wed, Oct 10, 2012 at 10:26 AM, Stefano Stabellini
> <stefano.stabellini@...citrix.com> wrote:
>> On Wed, 10 Oct 2012, Yinghai Lu wrote:
>>
>> It doesn't matter whether they come from BRK or other memory: Xen
>> assumes that all the pagetable pages come from
>> pgt_buf_start-pgt_buf_top, so if you are going to use another range you
>> need to tell Xen about it.
>>
>> Alternatively, you can follow Peter's suggestion and replace the current
>> hooks with a new one with a more precise and well defined semantic.
>> Something along the lines of "this pagetable page is about to be hooked
>> into the live pagetable". Xen would use the hook to mark it RO.
>
> attached patch on top of this patch will fix the problem?
>

  	.mapping = {
-		.pagetable_reserve		= native_pagetable_reserve,
+		.mark_page_ro			= mark_page_ro_noop;
  	},

I have already objected to this naming in the past, because it describes 
an implementation ("hypervisor make readonly") as opposed to a semantic 
function "make this page permissible to use as a page table".  I would 
call it pagetable_prepare or something like that.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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