arm64: smp: remove stack from secondary_data

When we boot a secondary CPU, we pass it a task and a stack to use. As
the stack is always the task's stack, which can be derived from the
task, let's have the secondary CPU derive this itself and avoid passing
redundant information.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Suzuki Poulose <suzuki.poulose@arm.com>
Cc: Will Deacon <will@kernel.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20210520115031.18509-5-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/arm64/include/asm/smp.h b/arch/arm64/include/asm/smp.h
index 0e35775..fc55f5a 100644 (file)
--- a/arch/arm64/include/asm/smp.h
+++ b/arch/arm64/include/asm/smp.h
@@ -73,12 +73,10 @@ asmlinkage void secondary_start_kernel(void);
 
 /*
  * Initial data for bringing up a secondary CPU.
- * @stack  - sp for the secondary CPU
  * @status - Result passed back from the secondary CPU to
  *           indicate failure.
  */
 struct secondary_data {
-       void *stack;
        struct task_struct *task;
        long status;
 };

diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 0cb34cc..4a5e204 100644 (file)
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -99,7 +99,6 @@ int main(void)
   DEFINE(SOFTIRQ_SHIFT, SOFTIRQ_SHIFT);
   DEFINE(IRQ_CPUSTAT_SOFTIRQ_PENDING, offsetof(irq_cpustat_t, __softirq_pending));
   BLANK();
-  DEFINE(CPU_BOOT_STACK,       offsetof(struct secondary_data, stack));
   DEFINE(CPU_BOOT_TASK,                offsetof(struct secondary_data, task));
   BLANK();
   DEFINE(FTR_OVR_VAL_OFFSET,   offsetof(struct arm64_ftr_override, val));

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index cc2d45d..9be95e1 100644 (file)
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -645,11 +645,12 @@ SYM_FUNC_START_LOCAL(__secondary_switched)
        isb
 
        adr_l   x0, secondary_data
-       ldr     x1, [x0, #CPU_BOOT_STACK]       // get secondary_data.stack
-       cbz     x1, __secondary_too_slow
-       mov     sp, x1
        ldr     x2, [x0, #CPU_BOOT_TASK]
        cbz     x2, __secondary_too_slow
+
+       ldr     x1, [x2, #TSK_STACK]
+       add     sp, x1, #THREAD_SIZE
+
        msr     sp_el0, x2
        scs_load x2, x3
        setup_final_frame

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 92e83e8..73625cc 100644 (file)
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -120,7 +120,6 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
         * page tables.
         */
        secondary_data.task = idle;
-       secondary_data.stack = task_stack_page(idle) + THREAD_SIZE;
        update_cpu_boot_status(CPU_MMU_OFF);
 
        /* Now bring the CPU into our world */
@@ -141,7 +140,6 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
 
        pr_crit("CPU%u: failed to come online\n", cpu);
        secondary_data.task = NULL;
-       secondary_data.stack = NULL;
        status = READ_ONCE(secondary_data.status);
        if (status == CPU_MMU_OFF)
                status = READ_ONCE(__early_cpu_boot_status);