Re: [PATCH v2 1/7] arm64: add CPU field to struct thread_info

Christophe Leroy
2021-09-30T13:23:19Z

Le 30/09/2021 à 15:20, Ard Biesheuvel a écrit :
> On Thu, 30 Sept 2021 at 15:15, Christophe Leroy
> <christophe.leroy@csgroup.eu> wrote:
>>
>>
>>
>> Le 30/09/2021 à 15:07, Ard Biesheuvel a écrit :
>>> On Thu, 30 Sept 2021 at 15:06, Christophe Leroy
>>> <christophe.leroy@csgroup.eu> wrote:
>>>>
>>>>
>>>>
>>>> Le 30/09/2021 à 14:58, Ard Biesheuvel a écrit :
>>>>> The CPU field will be moved back into thread_info even when
>>>>> THREAD_INFO_IN_TASK is enabled, so add it back to arm64's definition of
>>>>> struct thread_info.
>>>>>
>>>>> Note that arm64 always has CONFIG_SMP=y so there is no point in guarding
>>>>> the CPU field with an #ifdef.
>>>>>
>>>>> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
>>>>> Acked-by: Catalin Marinas <catalin.marinas@arm.com>
>>>>> Acked-by: Mark Rutland <mark.rutland@arm.com>
>>>>> ---
>>>>> arch/arm64/include/asm/thread_info.h | 1 +
>>>>> arch/arm64/kernel/asm-offsets.c | 1 +
>>>>> 2 files changed, 2 insertions(+)
>>>>>
>>>>> diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
>>>>> index 6623c99f0984..c02bc8c183c3 100644
>>>>> --- a/arch/arm64/include/asm/thread_info.h
>>>>> +++ b/arch/arm64/include/asm/thread_info.h
>>>>> @@ -42,6 +42,7 @@ struct thread_info {
>>>>> void *scs_base;
>>>>> void *scs_sp;
>>>>> #endif
>>>>> + u32 cpu;
>>>>> };
>>>>>
>>>>> #define thread_saved_pc(tsk) \
>>>>> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
>>>>> index 551427ae8cc5..cee9f3e9f906 100644
>>>>> --- a/arch/arm64/kernel/asm-offsets.c
>>>>> +++ b/arch/arm64/kernel/asm-offsets.c
>>>>> @@ -29,6 +29,7 @@ int main(void)
>>>>> DEFINE(TSK_ACTIVE_MM, offsetof(struct task_struct, active_mm));
>>>>> DEFINE(TSK_CPU, offsetof(struct task_struct, cpu));
>>>>> BLANK();
>>>>> + DEFINE(TSK_TI_CPU, offsetof(struct task_struct, thread_info.cpu));
>>>>
>>>> Why adding that now ? For powerpc you do the switch in 5.
>>>>
>>>
>>>
>>> Why not?
>>
>> Maybe to remain consistent between archs ?
>>
>
> Does it matter?

Probably not :)

>
>>>
>>>
>>>>> DEFINE(TSK_TI_FLAGS, offsetof(struct task_struct, thread_info.flags));
>>>>> DEFINE(TSK_TI_PREEMPT, offsetof(struct task_struct, thread_info.preempt_count));
>>>>> #ifdef CONFIG_ARM64_SW_TTBR0_PAN
>>>>>