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

[joeyli <jlee@suse.com>]

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