linux-kernel - Re: [PATCH v2 1/7] arm64: add CPU field to struct thread

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Message-ID: <6b003f58-48df-7ac4-4dbf-81b2c5bca5d9@csgroup.eu>
Date:   Thu, 30 Sep 2021 15:06:43 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Ard Biesheuvel <ardb@...nel.org>, linux-kernel@...r.kernel.org
Cc:     Keith Packard <keithpac@...zon.com>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v2 1/7] arm64: add CPU field to struct thread_info



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@...nel.org>
> Acked-by: Catalin Marinas <catalin.marinas@....com>
> Acked-by: Mark Rutland <mark.rutland@....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.

>     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
>