Re: [Resend][PATCH] x86/power/64: Always create temporary identity mapping correctly

On Mon, 8 Aug 2016, Rafael J. Wysocki wrote:

From: Rafael J. Wysocki <redacted>

The low-level resume-from-hibernation code on x86-64 uses
kernel_ident_mapping_init() to create the temoprary identity mapping,
but that function assumes that the offset between kernel virtual
addresses and physical addresses is aligned on the PGD level.

However, with a randomized identity mapping base, it may be aligned
on the PUD level and if that happens, the temporary identity mapping
created by set_up_temporary_mappings() will not reflect the actual
kernel identity mapping and the image restoration will fail as a
result (leading to a kernel panic most of the time).

To fix this problem, rework kernel_ident_mapping_init() to support
unaligned offsets between KVA and PA up to the PMD level and make
set_up_temporary_mappings() use it as approprtiate.

Reported-by: Thomas Garnier <redacted>
Suggested-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Rafael J. Wysocki <redacted>
Acked-by: Yinghai Lu <yinghai@kernel.org>
---

This is sort of urgent, because hibernation doesn't work with KASLR on x86-64
in 4.8-rc1 AFAICS and this should make them work together again.

Unless anyone sees any problems with it, I'll queue it up for 4.8-rc2.

Thomas, would it be possible to test it with KASLR enabled, please?

Unfortunately this applied on top of -rc1 still doesn't solve the reboot 
after reading hibernation image (I'd guess due to triple fault) with 
CONFIG_RANDOMIZE_MEMORY=y on my system.

With CONFIG_RANDOMIZE_MEMORY=n, the system resumes correctly.

-- 
Jiri Kosina
SUSE Labs