Now in the code, when interrupt and exception disturbs the user-space, always update SCTLR with cr_alignment. In our ARMv7 Cortex A15 SOC, the statements bracketed by CONFIG_ALIGNMENT_TRAP need about 100 cycles. it impacts our high realtime interrupt requirement scenario. Considering in ARMv6 and ARMv7 versions, cr_alignment and cr_no_alignment are always same without A bit, they are initialized by clearing A bit in alignment_init. So there is no need to update SCTLR if interrupt and exception disturbs the user-space in vector_swi function or alignment_trap macro, in the ARMv6 and ARMv7 chip. The patch has already verified in our ARMv7 Cortex A15 SOC. Signed-off-by: Wuqixuan <wuqix...@huawei.com> --- arch/arm/kernel/entry-common.S | 4 ++-- arch/arm/kernel/entry-header.S | 2 +- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S index a2dcafd..4b7686a 100644 --- a/arch/arm/kernel/entry-common.S +++ b/arch/arm/kernel/entry-common.S @@ -366,7 +366,7 @@ ENTRY(vector_swi) #endif zero_fp -#ifdef CONFIG_ALIGNMENT_TRAP +#if defined(CONFIG_ALIGNMENT_TRAP) && !(__LINUX_ARM_ARCH__ >= 6) ldr ip, __cr_alignment ldr ip, [ip] mcr p15, 0, ip, c1, c0 @ update control register @@ -490,7 +490,7 @@ __sys_trace_return: b ret_slow_syscall .align 5 -#ifdef CONFIG_ALIGNMENT_TRAP +#if defined(CONFIG_ALIGNMENT_TRAP) && !(__LINUX_ARM_ARCH__ >= 6) .type __cr_alignment, #object __cr_alignment: .word cr_alignment diff --git a/arch/arm/kernel/entry-header.S b/arch/arm/kernel/entry-header.S index 1420725..5eb9e59 100644 --- a/arch/arm/kernel/entry-header.S +++ b/arch/arm/kernel/entry-header.S @@ -38,7 +38,7 @@ .endm .macro alignment_trap, rtemp -#ifdef CONFIG_ALIGNMENT_TRAP +#if defined(CONFIG_ALIGNMENT_TRAP) && !(__LINUX_ARM_ARCH__ >= 6) ldr \rtemp, .LCcralign ldr \rtemp, [\rtemp] mcr p15, 0, \rtemp, c1, c0 -- 1.7.6-- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
