linux-kernel - Re: [PATCH v7u1 21/31] x86, kexec: only set ident mapping for ram.

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Date:	Mon, 14 Jan 2013 10:17:27 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Borislav Petkov <bp@...en8.de>, Yinghai Lu <yinghai@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jan Kiszka <jan.kiszka@....de>,
	Jason Wessel <jason.wessel@...driver.com>,
	linux-kernel@...r.kernel.org,
	Alexander Duyck <alexander.h.duyck@...el.com>
Subject: Re: [PATCH v7u1 21/31] x86, kexec: only set ident mapping for ram.

On Mon, Jan 14, 2013 at 1:53 AM, Borislav Petkov <bp@...en8.de> wrote:
> On Sun, Jan 13, 2013 at 09:46:17PM -0800, Yinghai Lu wrote:
>> On Sun, Jan 13, 2013 at 4:56 AM, Borislav Petkov <bp@...en8.de> wrote:
>> > On Thu, Jan 03, 2013 at 04:48:41PM -0800, Yinghai Lu wrote:
>> >> We should not set mapping for all under max_pfn.
>> >
>> > "We should not establish mappings for all memory under max_pfn."
>>
>> that is not accurate.
>>
>> We should not set mapping for all range under max_pfn.
>>
>> or
>>
>> We should set mappings only for memory ranges under max_pfn.
>
> Ok, that last thing is getting close. So do I understand it correctly
> now:
>
> "We should establish mappings only for memory (memory which is not
> marked reserved or whatever by E820 or some other mechanism) under
> max_pfn."
>
> ?

yes, you got it.

---
We should set mappings only for usable memory ranges under max_pfn
Otherwise causes same problem that is fixed by

        x86, mm: Only direct map addresses that are marked as E820_RAM

This patch exposes pfn_mapped array, and only sets ident mapping for ranges
in that array.

This patch relies on new kernel_ident_mapping_init that could handle existing
pgd/pud between different calls.

---
>
>> >> That causes same problem that is fixed by
>> >
>> > "Otherwise, it causes the same ..."
>> >
>> >>
>> >>       x86, mm: Only direct map addresses that are marked as E820_RAM
>> >
>> > You could add this patch's commit id since it is in tip:x86/mm2 and it
>> > shouldn't change: 66520ebc2df3.
>>
>> why ? they are not in linus tree yet, so it could change if that tip
>> branch is rebased.
>
> Oh, you didn't know: tip branches don't get rebased. At least almost
> never.

hpa rebased x86/mm2 one time with my patchset according to request from Ingo.
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