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Ard Biesheuvel 0edc78af73 arm64: mm: use single quantity to represent the PA to VA translation

commit 7bc1a0f9e1765830e945669c99c59c35cf9bca82 upstream.

On arm64, the global variable memstart_addr represents the physical
address of PAGE_OFFSET, and so physical to virtual translations or
vice versa used to come down to simple additions or subtractions
involving the values of PAGE_OFFSET and memstart_addr.

When support for 52-bit virtual addressing was introduced, we had to
deal with PAGE_OFFSET potentially being outside of the region that
can be covered by the virtual range (as the 52-bit VA capable build
needs to be able to run on systems that are only 48-bit VA capable),
and for this reason, another translation was introduced, and recorded
in the global variable physvirt_offset.

However, if we go back to the original definition of memstart_addr,
i.e., the physical address of PAGE_OFFSET, it turns out that there is
no need for two separate translations: instead, we can simply subtract
the size of the unaddressable VA space from memstart_addr to make the
available physical memory appear in the 48-bit addressable VA region.

This simplifies things, but also fixes a bug on KASLR builds, which
may update memstart_addr later on in arm64_memblock_init(), but fails
to update vmemmap and physvirt_offset accordingly.

Fixes: 5383cc6efed1 ("arm64: mm: Introduce vabits_actual")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Steve Capper <steve.capper@arm.com>
Link: https://lore.kernel.org/r/20201008153602.9467-2-ardb@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2021-01-30 13:54:10 +01:00

cache.S

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 234

2019-06-19 17:09:07 +02:00

context.c

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 234

2019-06-19 17:09:07 +02:00

copypage.c

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 234

2019-06-19 17:09:07 +02:00

dma-mapping.c

arm64: use asm-generic/dma-mapping.h