Re: [RFC PATCH] PM / hibernate: make sure each resuming page is in current memory zones

[chenyu5 <yu.c.chen@intel.com>]

On 2015年07月23日 13:34, joeyli wrote:
> Hi Chen Yu,
>
> On Wed, Jul 22, 2015 at 08:58:11AM +0000, Chen, Yu C wrote:
>>
>>
>>> -----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:
>>>> On 2015年07月16日 08:30, Rafael J. Wysocki wrote:
>>>>> On Monday, July 06, 2015 04:37:39 PM joeyli wrote:
>>>>>> Hi Chen Yu,
>>>>>>
>>>>>> On Thu, Jul 02, 2015 at 04:00:42PM +0800, chenyu5 wrote:
>>>>>>> Hi, Joey
>>>>>>> thanks for your reply,
>>>>>>>
>>>>>>> On 2015年07月02日 14:19, joeyli wrote:
>>>>>>>> Hi Chen Yu,
>>>>>>>>
>>>>>>>> On Tue, Jun 30, 2015 at 11:54:28PM +0800, Chen Yu wrote:
>>>>>>>>> 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:
>>>>>>>>>
>>>>>>>>> 1.Resuming page may also be in second kernel's e820 reserved
>>> region.
>>>>>>>>> BIOS-e820: [mem 0x0000000069d4f000-0x0000000069e12fff]
>>> reserved
>>>>>>>>> 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
>>>>>>>>> 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.
>>>>>>>>> Refer to https://bugzilla.kernel.org/show_bug.cgi?id=96111 for
>>> detail.
>>>>>>>>>
>>>>>>>>
>>>>>>>> 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.
>>>>>>>
>>>>>>>
>>>>>>>> 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.
>>>>>>>>
>>>>>>>>
>>>>>>>> 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 <joeyli.kernel@gmail.com>
>>>>>
>>>>> 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
>>>
>
> 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.
>
OK. I'll wait for Yinghai's patch and yours.
Thanks.

Yu
>
> Regards
> Joey Lee
>