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

[Christophe Leroy]

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