diff options
| author | Ard Biesheuvel <ardb@kernel.org> | 2020-10-08 17:35:59 +0200 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2020-10-15 11:14:57 +0100 |
| commit | 7bc1a0f9e1765830e945669c99c59c35cf9bca82 (patch) | |
| tree | d52db7b64e7bd9cb4e0c4e3dd592f54cb2f7c43e /arch/arm64/include/asm/pgtable.h | |
| parent | 4b7a6ce71e033666d6f5a577deb7f1f5126ed889 (diff) | |
arm64: mm: use single quantity to represent the PA to VA translation
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>
Diffstat (limited to 'arch/arm64/include/asm/pgtable.h')
| -rw-r--r-- | arch/arm64/include/asm/pgtable.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index a11bf52e0c38..4ff12a7adcfd 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -24,6 +24,8 @@ #define VMALLOC_START (MODULES_END) #define VMALLOC_END (- PUD_SIZE - VMEMMAP_SIZE - SZ_64K) +#define vmemmap ((struct page *)VMEMMAP_START - (memstart_addr >> PAGE_SHIFT)) + #define FIRST_USER_ADDRESS 0UL #ifndef __ASSEMBLY__ @@ -34,8 +36,6 @@ #include <linux/mm_types.h> #include <linux/sched.h> -extern struct page *vmemmap; - #ifdef CONFIG_TRANSPARENT_HUGEPAGE #define __HAVE_ARCH_FLUSH_PMD_TLB_RANGE |