diff options
| author | Steve Capper | 2018-12-06 22:50:41 +0000 |
|---|---|---|
| committer | Will Deacon | 2018-12-10 18:42:17 +0000 |
| commit | 67e7fdfcc6824a4f768d76d89377b33baad58fad (patch) | |
| tree | b53aaa1c9e7bf1853f2725374daedf690d0ee0cb /arch/arm64/Kconfig | |
| parent | a96a33b1ca57dbea4285893dedf290aeb8eb090b (diff) | |
arm64: mm: introduce 52-bit userspace support
On arm64 there is optional support for a 52-bit virtual address space.
To exploit this one has to be running with a 64KB page size and be
running on hardware that supports this.
For an arm64 kernel supporting a 48 bit VA with a 64KB page size,
some changes are needed to support a 52-bit userspace:
* TCR_EL1.T0SZ needs to be 12 instead of 16,
* TASK_SIZE needs to reflect the new size.
This patch implements the above when the support for 52-bit VAs is
detected at early boot time.
On arm64 userspace addresses translation is controlled by TTBR0_EL1. As
well as userspace, TTBR0_EL1 controls:
* The identity mapping,
* EFI runtime code.
It is possible to run a kernel with an identity mapping that has a
larger VA size than userspace (and for this case __cpu_set_tcr_t0sz()
would set TCR_EL1.T0SZ as appropriate). However, when the conditions for
52-bit userspace are met; it is possible to keep TCR_EL1.T0SZ fixed at
12. Thus in this patch, the TCR_EL1.T0SZ size changing logic is
disabled.
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Steve Capper <steve.capper@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/Kconfig')
| -rw-r--r-- | arch/arm64/Kconfig | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 6d2b25f51bb3..858e353b2f40 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -716,6 +716,10 @@ config ARM64_PA_BITS_52 endchoice +config ARM64_52BIT_VA + def_bool y + depends on ARM64_VA_BITS_48 && ARM64_64K_PAGES && (ARM64_PAN || !ARM64_SW_TTBR0_PAN) + config ARM64_PA_BITS int default 48 if ARM64_PA_BITS_48 |