[PATCH 1/6] arm64: don't override idmap t0sz

[Anshuman Khandual]

From: Mark Rutland <mark.rutland at arm.com>

When the kernel is built with CONFIG_ARM64_VA_BITS_52, __cpu_setup will
override `idmap_t0sz`, and program TCR_EL1.T0SZ based on
`vabits_actual`. This is inconsistent with cpu_set_idmap_tcr_t0sz(),
which will use `idmap_t0sz`, but happens to work as
CONFIG_ARM64_VA_BITS_52 requires 64K pages where 48-bit VAs and 52-bit
VAs required the same number of page table levels and TTBR0 addresses
grow upwards from the base of the PGD table (for which the entire page
is zeroed).

When switching away from the idmap, cpu_set_default_tcr_t0sz() will use
`vabits_actual`, and so the T0SZ value used for the idmap does not have
to match the T0SZ used during regular kernel/userspace execution.

This patch ensures we *always* use `idmap_t0sz` as the TCR_EL1.T0SZ
value used while the idmap is active.

Cc: Ard Biesheuvel <ardb at kernel.org>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Will Deacon <will at kernel.org>
Signed-off-by: Mark Rutland <mark.rutland at arm.com>
Signed-off-by: Anshuman Khandual <anshuman.khandual at arm.com>
---
 arch/arm64/mm/proc.S | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index 50bbed947bec..c1f76bf3276c 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -468,9 +468,8 @@ SYM_FUNC_START(__cpu_setup)
 	sub		x9, xzr, x9
 	add		x9, x9, #64
 	tcr_set_t1sz	tcr, x9
-#else
-	ldr_l		x9, idmap_t0sz
 #endif
+	ldr_l		x9, idmap_t0sz
 	tcr_set_t0sz	tcr, x9
 
 	/*
-- 
2.20.1