[PATCH 17/19] arm64: smp: Pass secondary CPU boot parameters via firmware if possible

[Will Deacon]

In preparation for parallel bringup of secondary CPUs, the global
'secondary_data' structure used for initial paramater passing must be
localised.

Pass the idle 'task_struct' pointer for secondary CPUs directly to
->cpu_boot() if the backend supports it.

Signed-off-by: Will Deacon <will at kernel.org>
---
 arch/arm64/include/asm/smp.h |  1 +
 arch/arm64/kernel/head.S     | 12 +++++++++++-
 arch/arm64/kernel/psci.c     |  4 ++--
 arch/arm64/kernel/smp.c      | 25 +++++++++++--------------
 4 files changed, 25 insertions(+), 17 deletions(-)

diff --git a/arch/arm64/include/asm/smp.h b/arch/arm64/include/asm/smp.h
index 7b986a6a765b..7f2cd84b7785 100644
--- a/arch/arm64/include/asm/smp.h
+++ b/arch/arm64/include/asm/smp.h
@@ -95,6 +95,7 @@ struct secondary_data {
 extern struct secondary_data secondary_data;
 extern long __early_cpu_boot_status;
 extern void secondary_entry(void);
+extern void secondary_entry_with_arg(void);
 
 extern void arch_send_call_function_single_ipi(int cpu);
 extern void arch_send_call_function_ipi_mask(const struct cpumask *mask);
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 87a822e5c4ca..17868b497d7c 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -335,6 +335,7 @@ SYM_FUNC_END(init_kernel_el)
 	 * cores are held until we're ready for them to initialise.
 	 */
 SYM_FUNC_START(secondary_holding_pen)
+	mov	x19, xzr
 	mov	x0, xzr
 	bl	init_kernel_el			// w0=cpu_boot_mode
 	mrs	x2, mpidr_el1
@@ -353,10 +354,16 @@ SYM_FUNC_END(secondary_holding_pen)
 	 * be used where CPUs are brought online dynamically by the kernel.
 	 */
 SYM_FUNC_START(secondary_entry)
+	mov	x0, xzr
+	b	secondary_entry_with_arg
+SYM_FUNC_END(secondary_entry)
+
+SYM_FUNC_START(secondary_entry_with_arg)
+	mov	x19, x0
 	mov	x0, xzr
 	bl	init_kernel_el			// w0=cpu_boot_mode
 	b	secondary_startup
-SYM_FUNC_END(secondary_entry)
+SYM_FUNC_END(secondary_entry_with_arg)
 
 SYM_FUNC_START_LOCAL(secondary_startup)
 	/*
@@ -391,10 +398,13 @@ SYM_FUNC_START_LOCAL(__secondary_switched)
 	msr	vbar_el1, x5
 	isb
 
+	mov	x2, x19
+	cbnz	x2, 1f
 	adr_l	x0, secondary_data
 	ldr	x2, [x0, #CPU_BOOT_TASK]
 	cbz	x2, __secondary_too_slow
 
+1:
 	init_cpu_task x2, x1, x3
 
 #ifdef CONFIG_ARM64_PTR_AUTH
diff --git a/arch/arm64/kernel/psci.c b/arch/arm64/kernel/psci.c
index 3ba4fa14b9e3..c13e635e8a11 100644
--- a/arch/arm64/kernel/psci.c
+++ b/arch/arm64/kernel/psci.c
@@ -38,8 +38,8 @@ static int __init cpu_psci_cpu_prepare(unsigned int cpu)
 
 static int cpu_psci_cpu_boot(unsigned int cpu, unsigned long context)
 {
-	phys_addr_t pa_secondary_entry = __pa_symbol(secondary_entry);
-	int err = psci_ops.cpu_on(cpu_logical_map(cpu), pa_secondary_entry,
+	void *entry_va = context ? secondary_entry_with_arg : secondary_entry;
+	int err = psci_ops.cpu_on(cpu_logical_map(cpu), __pa_symbol(entry_va),
 				  context);
 	if (err && err != -EPERM)
 		pr_err("failed to boot CPU%d (%d)\n", cpu, err);
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index b57f8f752f78..95d5328c3f5a 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -93,34 +93,31 @@ static inline int op_cpu_kill(unsigned int cpu)
 }
 #endif
 
-
 /*
  * Boot a secondary CPU, and assign it the specified idle task.
  * This also gives us the initial stack to use for this CPU.
  */
-static int boot_secondary(unsigned int cpu, struct task_struct *idle)
-{
-	const struct cpu_operations *ops = get_secondary_cpu_ops();
-
-	if (ops->cpu_boot)
-		return ops->cpu_boot(cpu, 0);
-
-	return -EOPNOTSUPP;
-}
-
 int arch_cpuhp_kick_ap_alive(unsigned int cpu, struct task_struct *idle)
 {
-	int ret;
+	const struct cpu_operations *ops = get_secondary_cpu_ops();
+	int ret = -EOPNOTSUPP;
+	void *arg = NULL;
 
 	/*
 	 * We need to tell the secondary core where to find its stack and the
 	 * page tables.
 	 */
-	secondary_data.task = idle;
+	if (ops->cpu_boot_has_arg && ops->cpu_boot_has_arg())
+		arg = idle;
+	else
+		secondary_data.task = idle;
+
 	update_cpu_boot_status(CPU_MMU_OFF);
 
 	/* Now bring the CPU into our world */
-	ret = boot_secondary(cpu, idle);
+	if (ops->cpu_boot)
+		ret = ops->cpu_boot(cpu, (unsigned long)arg);
+
 	if (ret && ret != -EPERM)
 		pr_err("CPU%u: failed to boot: %d\n", cpu, ret);
 	return ret;
-- 
2.55.0.979.g7e5102b832-goog