[PATCH v32 07/13] arm64: hibernate: preserve kdump image around hibernation

On Wed, Feb 15, 2017 at 12:12:35PM +0000, James Morse wrote:

Hi Akashi,

On 07/02/17 08:08, AKASHI Takahiro wrote:

quoted

Since arch_kexec_protect_crashkres() removes a mapping for crash dump
kernel memory, the loaded contents won't be preserved around hibernation.

In this patch, arch_kexec_(un)protect_crashkres() are additionally called
before/after hibernation so that the relevant region will be mapped again
and restored just as the other memory regions are.

Reviewed-by: James Morse <james.morse@arm.com>

Thank you very much.

A quick test of this took longer than expected (writing to a slow usb device),

Really? I use a uSD card on hikey as a swap device, and it takes just
a few moments to save a hibernate image although I do the test right after
the system comes up.

I
suspect it is save/restoring the whole crash region (which I don't think is a
problem).

Now that we have only page-level mappings for the crash region,
it might be possible to mark all the unused pages "reserved"
in arch_kexec_unprotect_crashkres() if called in hibernate.

-Takahiro AKASHI

If someone turns out to use this combination of features I will look
at improving this, (almost certainly requires core-code changes).


Thanks,

James