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SubjectRe: [PATCH v2] riscv: Setup exception vector for nommu platform
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On Thu, 13 Aug 2020 01:49:44 PDT (-0700), anup@brainfault.org wrote:
> On Thu, Aug 13, 2020 at 9:10 AM Qiu Wenbo <qiuwenbo@phytium.com.cn> wrote:
>>
>> Exception vector is missing on nommu platform and that is an issue.
>> This patch is tested in Sipeed Maix Bit Dev Board.
>>
>> Fixes: 79b1feba5455 ("RISC-V: Setup exception vector early")
>> Suggested-by: Anup Patel <anup@brainfault.org>
>> Suggested-by: Atish Patra <atishp@atishpatra.org>
>> Signed-off-by: Qiu Wenbo <qiuwenbo@phytium.com.cn>
>> ---
>> arch/riscv/kernel/head.S | 25 +++++++++++++++++--------
>> 1 file changed, 17 insertions(+), 8 deletions(-)
>>
>> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
>> index d0c5c316e9bb..0a4e81b8dc79 100644
>> --- a/arch/riscv/kernel/head.S
>> +++ b/arch/riscv/kernel/head.S
>> @@ -77,16 +77,10 @@ relocate:
>> csrw CSR_SATP, a0
>> .align 2
>> 1:
>> - /* Set trap vector to exception handler */
>> - la a0, handle_exception
>> + /* Set trap vector to spin forever to help debug */
>> + la a0, .Lsecondary_park
>> csrw CSR_TVEC, a0
>>
>> - /*
>> - * Set sup0 scratch register to 0, indicating to exception vector that
>> - * we are presently executing in kernel.
>> - */
>> - csrw CSR_SCRATCH, zero
>> -
>> /* Reload the global pointer */
>> .option push
>> .option norelax
>> @@ -144,9 +138,23 @@ secondary_start_common:
>> la a0, swapper_pg_dir
>> call relocate
>> #endif
>> + call setup_trap_vector
>> tail smp_callin
>> #endif /* CONFIG_SMP */
>>
>> +.align 2
>> +setup_trap_vector:
>> + /* Set trap vector to exception handler */
>> + la a0, handle_exception
>> + csrw CSR_TVEC, a0
>> +
>> + /*
>> + * Set sup0 scratch register to 0, indicating to exception vector that
>> + * we are presently executing in kernel.
>> + */
>> + csrw CSR_SCRATCH, zero
>> + ret
>> +
>> .Lsecondary_park:
>> /* We lack SMP support or have too many harts, so park this hart */
>> wfi
>> @@ -240,6 +248,7 @@ clear_bss_done:
>> call relocate
>> #endif /* CONFIG_MMU */
>>
>> + call setup_trap_vector
>> /* Restore C environment */
>> la tp, init_task
>> sw zero, TASK_TI_CPU(tp)
>> --
>> 2.28.0
>>
>
> Looks good to me.
>
> Reviewed-by: Anup Patel <anup@brainfault.org>
>
> Regards,
> Anup

Thanks, this is on fixes.

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