Messages in this thread | | | From | Ard Biesheuvel <> | Date | Sun, 5 Sep 2021 22:25:37 +0200 | Subject | Re: [PATCH 1/3] ARM: Pass cpu number to secondary_start_kernel |
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Hi Keith,
This looks like a worthwhile cleanup to me regardless of the following patches.
On Sat, 4 Sept 2021 at 08:09, Keith Packard <keithp@keithp.com> wrote: > > Instead of pulling the CPU value out of the thread_info struct, pass > it as an argument. When first initializing secondary processors, this > is done by stashing the value in the secondary_data struct. When > restarting idle processors, the previous CPU value is passed. > > Because the cpu is now known at the top of secondary_start_kernel, the > per_cpu_offset value can now be set at this point, instead of in > cpu_init where it was also incorrectly setting the per_cpu_offset for > the boot processor before that value had been computed. > > Signed-off-by: Keith Packard <keithpac@amazon.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
> --- > arch/arm/include/asm/smp.h | 3 ++- > arch/arm/kernel/head-nommu.S | 1 + > arch/arm/kernel/head.S | 1 + > arch/arm/kernel/setup.c | 6 ------ > arch/arm/kernel/smp.c | 14 +++++++++----- > 5 files changed, 13 insertions(+), 12 deletions(-) > > diff --git a/arch/arm/include/asm/smp.h b/arch/arm/include/asm/smp.h > index 5d508f5d56c4..86a7fd721556 100644 > --- a/arch/arm/include/asm/smp.h > +++ b/arch/arm/include/asm/smp.h > @@ -48,7 +48,7 @@ extern void set_smp_ipi_range(int ipi_base, int nr_ipi); > * Called from platform specific assembly code, this is the > * secondary CPU entry point. > */ > -asmlinkage void secondary_start_kernel(void); > +asmlinkage void secondary_start_kernel(unsigned int cpu); > > > /* > @@ -61,6 +61,7 @@ struct secondary_data { > }; > unsigned long swapper_pg_dir; > void *stack; > + unsigned int cpu; > }; > extern struct secondary_data secondary_data; > extern void secondary_startup(void); > diff --git a/arch/arm/kernel/head-nommu.S b/arch/arm/kernel/head-nommu.S > index 0fc814bbc34b..5aa8ef42717f 100644 > --- a/arch/arm/kernel/head-nommu.S > +++ b/arch/arm/kernel/head-nommu.S > @@ -114,6 +114,7 @@ ENTRY(secondary_startup) > add r12, r12, r10 > ret r12 > 1: bl __after_proc_init > + ldr r0, [r7, #16] @ set up cpu number > ldr sp, [r7, #12] @ set up the stack pointer > mov fp, #0 > b secondary_start_kernel > diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S > index 7f62c5eccdf3..0e541af738e2 100644 > --- a/arch/arm/kernel/head.S > +++ b/arch/arm/kernel/head.S > @@ -394,6 +394,7 @@ ENDPROC(secondary_startup_arm) > > ENTRY(__secondary_switched) > ldr_l r7, secondary_data + 12 @ get secondary_data.stack > + ldr_l r0, secondary_data + 16 @ get secondary_data.cpu > mov sp, r7 > mov fp, #0 > b secondary_start_kernel > diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c > index 73ca7797b92f..ca0201635fac 100644 > --- a/arch/arm/kernel/setup.c > +++ b/arch/arm/kernel/setup.c > @@ -532,12 +532,6 @@ void notrace cpu_init(void) > BUG(); > } > > - /* > - * This only works on resume and secondary cores. For booting on the > - * boot cpu, smp_prepare_boot_cpu is called after percpu area setup. > - */ > - set_my_cpu_offset(per_cpu_offset(cpu)); > - > cpu_proc_init(); > > /* > diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c > index 74679240a9d8..55cb1689a4b3 100644 > --- a/arch/arm/kernel/smp.c > +++ b/arch/arm/kernel/smp.c > @@ -153,6 +153,7 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle) > secondary_data.pgdir = virt_to_phys(idmap_pgd); > secondary_data.swapper_pg_dir = get_arch_pgd(swapper_pg_dir); > #endif > + secondary_data.cpu = cpu; > sync_cache_w(&secondary_data); > > /* > @@ -373,11 +374,14 @@ void arch_cpu_idle_dead(void) > * cpu initialisation. There's some initialisation which needs > * to be repeated to undo the effects of taking the CPU offline. > */ > - __asm__("mov sp, %0\n" > + __asm__("mov r0, %1\n" > + " mov sp, %0\n" > " mov fp, #0\n" > " b secondary_start_kernel" > : > - : "r" (task_stack_page(current) + THREAD_SIZE - 8)); > + : "r" (task_stack_page(current) + THREAD_SIZE - 8), > + "r" (cpu) > + : "r0"); > } > #endif /* CONFIG_HOTPLUG_CPU */ > > @@ -400,10 +404,11 @@ static void smp_store_cpu_info(unsigned int cpuid) > * This is the secondary CPU boot entry. We're using this CPUs > * idle thread stack, but a set of temporary page tables. > */ > -asmlinkage void secondary_start_kernel(void) > +asmlinkage void secondary_start_kernel(unsigned int cpu) > { > struct mm_struct *mm = &init_mm; > - unsigned int cpu; > + > + set_my_cpu_offset(per_cpu_offset(cpu)); > > secondary_biglittle_init(); > > @@ -420,7 +425,6 @@ asmlinkage void secondary_start_kernel(void) > * All kernel threads share the same mm context; grab a > * reference and switch to it. > */ > - cpu = smp_processor_id(); > mmgrab(mm); > current->active_mm = mm; > cpumask_set_cpu(cpu, mm_cpumask(mm)); > -- > 2.33.0 >
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