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

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?

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


Thanks a lot!
Joey Lee