On Wed, Apr 29, 2020 at 1:01 PM James Morse [off-list ref] wrote:

Hi Pavel,

On 26/03/2020 03:24, Pavel Tatashin wrote:

quoted

From: James Morse <james.morse@arm.com>

To resume from hibernate, the contents of memory are restored from
the swap image. This may overwrite any page, including the running
kernel and its page tables.

Hibernate copies the code it uses to do the restore into a single
page that it knows won't be overwritten, and maps it with page tables
built from pages that won't be overwritten.

Today the address it uses for this mapping is arbitrary, but to allow
kexec to reuse this code, it needs to be idmapped. To idmap the page
we must avoid the kernel helpers that have VA_BITS baked in.

Convert create_single_mapping() to take a single PA, and idmap it.
The page tables are built in the reverse order to normal using
pfn_pte() to stir in any bits between 52:48. T0SZ is always increased
to cover 48bits, or 52 if the copy code has bits 52:48 in its PA.

Pasha: The original patch from James
inux-arm-kernel/20200115143322.214247-4-james.morse@arm.com

-EBROKENLINK

The convention is to use a 'Link:' tag in the signed-off area.
e.g. 5a3577039cbe

OK Fixed.

quoted

Adopted it to trans_pgd, so it can be commonly used by both Kexec
and Hibernate. Some minor clean-ups.

Please describe your changes just before your SoB. This means each author sign's off on
the stuff above their SoB, and its obvious who made which changes.

Search for 'Lucky K Maintainer' in process/submitting-patches.rst for an example.

OK, Fixed.
eed the maximum T0SZ.

quoted

+ *
+ * Returns 0 on success, and -ENOMEM on failure.
+ * On success trans_ttbr0 contains page table with idmapped page, t0sz is set to

quoted

+ * maxumum T0SZ for this page.

maxumum

Ok.

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