Hi Chen Yu,

On Wed, Jul 22, 2015 at 08:58:11AM +0000, Chen, Yu C wrote:

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-----Original Message-----
From: Rafael J. Wysocki [mailto:rjw@rjwysocki.net]
Sent: Wednesday, July 22, 2015 9:04 AM
To: Chen, Yu C
Cc: linux-pm@vger.kernel.org; Wysocki, Rafael J; joeyli; Tian, YeX
Subject: Re: [RFC PATCH] PM / hibernate: make sure each resuming page is
in current memory zones

On Tuesday, July 21, 2015 09:28:32 AM chenyu5 wrote:

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On 2015年07月16日 08:30, Rafael J. Wysocki wrote:

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On Monday, July 06, 2015 04:37:39 PM joeyli wrote:

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Hi Chen Yu,

On Thu, Jul 02, 2015 at 04:00:42PM +0800, chenyu5 wrote:

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Hi, Joey
thanks for your reply,

On 2015年07月02日 14:19, joeyli wrote:

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Hi Chen Yu,

On Tue, Jun 30, 2015 at 11:54:28PM +0800, Chen Yu wrote:

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Commit 84c91b7ae07c ("PM / hibernate: avoid unsafe pages in e820
reserved
regions") was reverted, because this patch makes resume from
hibernation on Lenovo x230 unreliable. But reverting may bring
back the kernel exception firstly reported in former patch. In
general, there are three problems in current code when resuming

from hibernation:

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1.Resuming page may also be in second kernel's e820 reserved

region.

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BIOS-e820: [mem 0x0000000069d4f000-0x0000000069e12fff]

reserved

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this causes kernel exception described in Commit 84c91b7ae07c
("PM / hibernate: avoid unsafe pages in e820 reserved regions")

2.If Commit 84c91b7ae07c ("PM / hibernate: avoid unsafe pages in
e820 reserved regions") is applied to fix problem 1, and if
E820_RESERVED_KERN regions causes some regions at e820 table

not

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page aligned, e820_mark_nosave_regions will misjudgment the
non-page aligned space to be "hole" space and add to nosave

regions, this causes resuming failed.

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Refer to https://bugzilla.kernel.org/show_bug.cgi?id=96111 for

detail.

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Sorry for I am not fully understand why checking pfn_valid could
avoid the above 2. issue?

[Yu] According to e820_mark_nosave_regions, two kinds of e820
regions will be regarded as nosave:
a.e820.map holes between each e820entry b.e820entry with
(!E820_RAM && !E820_RESERVED_KERN) dmesg in
https://bugzilla.kernel.org/show_bug.cgi?id=96111
shows that:

BIOS-e820: [mem 0x000000005baff000-0x00000000d684ffff] usable
reserve setup_data: [mem 0x000000009d3e0018-0x000000009d3f0057]
usable
PM: Registered nosave memory: [mem 0x9d3e0000-0x9d3e0fff]

e820 map was changed by situation a, but it should not be added to
nosave list, right?

and according to saveable_page, only pages in the zone will be saved:
if (page_zone(page_ != zone)
	return NULL;

The function of is_valid_orig_page in this patch treats setup_data
as valid page, so I think this workaround issue 2.

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Per my understood should waiting Yinghai Lu's patches for killing
E820_RESERVED_KERN to avoid the aligned problem.

[Yu] yes, it is a graceful solution, but I don't see that in 4.1?
And we encountered problem 3 in our testing enviroment, so I wrote
a patch to deal with it first.

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Thanks a lot!
Joey Lee

Thanks for your explanation, then your patch makes sense to me.

Please feel free to add tag:

Reviewed-by: Lee, Chun-Yi <redacted>

Patch queued up for 4.3, thanks!

Hi Rafeal,
Please help drop this patch for now, QA has found some problems with
this patch applied, we're working on it now. Sorry for inconvenience.

Dropping, thanks for the heads up!

Hi,Rafeal, Joey
I've sent out another patch, it is based on Joey's 
original patch, and it treats any adjacent E820_RAM/E820_RESERVED_KERN regions as
one. In this way,  non-page-aligned setup_data address would not be added 
to nosave regions, thus workaround the hibernation failor mentiones in
https://bugzilla.kernel.org/show_bug.cgi?id=96111

V1 patch has a problem that, NOT every page in page zone has a valid mapping address , thus
accessing these pages would cause problem. So I rewrite this path and send out another V2 version.
Thanks for your time.

 Yu

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Thanks for your work on this patch, but the E820_RESERVED_KERN will be removed
anyhow. So I prefer waiting Yinghai Lu's patch for killing E820_RESERVED_KERN.


Regards
Joey Lee