Reading TTBCR in early boot stage might return the value of the previous kernel's configuration, especially in case of kexec. For example, if normal kernel (first kernel) had run on a configuration of PHYS_OFFSET <= PAGE_OFFSET and crash kernel (second kernel) is running on a configuration PHYS_OFFSET > PAGE_OFFSET, which can happen because it depends on the reserved area for crash kernel, reading TTBCR and using the value to OR other bit fields might be risky because it doesn't have a reset value for TTBCR.
Acked-by: Russell King <rmk+ker...@armlinux.org.uk> Suggested-by: Robin Murphy <robin.mur...@arm.com> Signed-off-by: Hoeun Ryu <hoeun....@gmail.com> --- * add Acked-by: Russell King <rmk+ker...@armlinux.org.uk> * v1: amended based on - "[PATCHv2] arm: LPAE: kexec: clear TTBCR.T1SZ explicitly when PHYS_OFFSET > PAGE_OFFSET" - https://lkml.org/lkml/2017/6/5/239 arch/arm/mm/proc-v7-3level.S | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/arm/mm/proc-v7-3level.S b/arch/arm/mm/proc-v7-3level.S index 5e5720e..7d16bbc 100644 --- a/arch/arm/mm/proc-v7-3level.S +++ b/arch/arm/mm/proc-v7-3level.S @@ -129,8 +129,7 @@ ENDPROC(cpu_v7_set_pte_ext) .macro v7_ttb_setup, zero, ttbr0l, ttbr0h, ttbr1, tmp ldr \tmp, =swapper_pg_dir @ swapper_pg_dir virtual address cmp \ttbr1, \tmp, lsr #12 @ PHYS_OFFSET > PAGE_OFFSET? - mrc p15, 0, \tmp, c2, c0, 2 @ TTB control egister - orr \tmp, \tmp, #TTB_EAE + mov \tmp, #TTB_EAE @ for TTB control egister ALT_SMP(orr \tmp, \tmp, #TTB_FLAGS_SMP) ALT_UP(orr \tmp, \tmp, #TTB_FLAGS_UP) ALT_SMP(orr \tmp, \tmp, #TTB_FLAGS_SMP << 16) -- 2.7.4