linux-kernel - Re: [PATCH] x86/mm/init: respect memblock reserved regions when destroying mappings

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Message-ID: <4D504161.2060900@kernel.org>
Date:	Mon, 07 Feb 2011 11:00:49 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
CC:	"H. Peter Anvin" <hpa@...or.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"x86@...nel.org" <x86@...nel.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Jan Beulich <JBeulich@...ell.com>
Subject: Re: [PATCH] x86/mm/init: respect memblock reserved regions when destroying
 mappings

On 02/07/2011 10:58 AM, Stefano Stabellini wrote:
> On Mon, 7 Feb 2011, Yinghai Lu wrote:
>> On 02/07/2011 08:50 AM, Stefano Stabellini wrote:
>>> On Sun, 6 Feb 2011, Yinghai Lu wrote:
>>>> On 02/05/2011 11:30 PM, H. Peter Anvin wrote:
>>>>> On 02/05/2011 11:02 PM, Yinghai Lu wrote:
>>>>>> why not just move calling cleanup_highmap down?
>>>>>>
>>>>>> something like attached patch.
>>>>>
>>>>> This patch looks very clean and looks on the surface of it like it is
>>>>> removing some ugly ad hoc code, but (as always) it needs a description
>>>>> about the problem it solves and why it is correct.
>>>>
>>>> Sure.
>>>>
>>>>
>>>> Jeremy and xen guys, can you please check if it works well with xen ?
>>>>
>>>
>>> Actually this patch makes things worse on xen, because before
>>> cleanup_highmap() wasn't called at all on xen (on purpose) and now it
>>> is, fully destroying all the mappings we have at _end.
>>>
>>> Can we add a check on memblock reserved regions in cleanup_highmap()?
>>> Otherwise could we avoid calling cleanup_highmap() at all on xen?
>>
>> why DO xen need over-mapped kernel initial mapping?
>>
>> what is in that range after _end to 512M?
> 
> The mfn list that is the list of machine frame numbers assigned to this
> domain; it is used across the kernel to convert pfns into mfns.
> It passed to us at that address by the domain builder.

is it possible for you to pass physical address, and then map it in kernel?
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