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

From: Christophe Leroy
Date: Thu Sep 30 2021 - 09:23:19 EST




Le 30/09/2021 à 15:20, Ard Biesheuvel a écrit :
On Thu, 30 Sept 2021 at 15:15, Christophe Leroy
<christophe.leroy@xxxxxxxxxx> wrote:



Le 30/09/2021 à 15:07, Ard Biesheuvel a écrit :
On Thu, 30 Sept 2021 at 15:06, Christophe Leroy
<christophe.leroy@xxxxxxxxxx> 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@xxxxxxxxxx>
Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Acked-by: Mark Rutland <mark.rutland@xxxxxxx>
---
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