path: root/arch/arm64/Kconfig
diff options
authorSteve Capper <steve.capper@arm.com>2018-12-06 22:50:41 +0000
committerWill Deacon <will.deacon@arm.com>2018-12-10 18:42:17 +0000
commit67e7fdfcc6824a4f768d76d89377b33baad58fad (patch)
treeb53aaa1c9e7bf1853f2725374daedf690d0ee0cb /arch/arm64/Kconfig
parentarm64: mm: Prevent mismatched 52-bit VA support (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 '')
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
+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
default 48 if ARM64_PA_BITS_48