Merge patch series "riscv: CPU operations cleanup"

Samuel Holland <samuel.holland@sifive.com> says:

This series cleans up some duplicated and dead code around the RISC-V
CPU operations, that was copied from arm64 but is not needed here. The
result is a bit of memory savings and removal of a few SBI calls during
boot, with no functional change.

* b4-shazam-merge:
  riscv: Use the same CPU operations for all CPUs
  riscv: Remove unused members from struct cpu_operations
  riscv: Deduplicate code in setup_smp()

Link: https://lore.kernel.org/r/20231121234736.3489608-1-samuel.holland@sifive.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/include/asm/cpu_ops.h

@@ -13,33 +13,23 @@
 /**
  * struct cpu_operations - Callback operations for hotplugging CPUs.
  *
- * @name:		Name of the boot protocol.
- * @cpu_prepare:	Early one-time preparation step for a cpu. If there
- *			is a mechanism for doing so, tests whether it is
- *			possible to boot the given HART.
  * @cpu_start:		Boots a cpu into the kernel.
- * @cpu_disable:	Prepares a cpu to die. May fail for some
- *			mechanism-specific reason, which will cause the hot
- *			unplug to be aborted. Called from the cpu to be killed.
  * @cpu_stop:		Makes a cpu leave the kernel. Must not fail. Called from
  *			the cpu being stopped.
  * @cpu_is_stopped:	Ensures a cpu has left the kernel. Called from another
  *			cpu.
  */
 struct cpu_operations {
-	const char	*name;
-	int		(*cpu_prepare)(unsigned int cpu);
 	int		(*cpu_start)(unsigned int cpu,
 				     struct task_struct *tidle);
 #ifdef CONFIG_HOTPLUG_CPU
-	int		(*cpu_disable)(unsigned int cpu);
 	void		(*cpu_stop)(void);
 	int		(*cpu_is_stopped)(unsigned int cpu);
 #endif
 };
 
 extern const struct cpu_operations cpu_ops_spinwait;
-extern const struct cpu_operations *cpu_ops[NR_CPUS];
-void __init cpu_set_ops(int cpu);
+extern const struct cpu_operations *cpu_ops;
+void __init cpu_set_ops(void);
 
 #endif /* ifndef __ASM_CPU_OPS_H */

arch/riscv/kernel/cpu-hotplug.c

@@ -18,7 +18,7 @@
 
 bool cpu_has_hotplug(unsigned int cpu)
 {
-	if (cpu_ops[cpu]->cpu_stop)
+	if (cpu_ops->cpu_stop)
 		return true;
 
 	return false;
@@ -29,25 +29,18 @@ bool cpu_has_hotplug(unsigned int cpu)
  */
 int __cpu_disable(void)
 {
-	int ret = 0;
 	unsigned int cpu = smp_processor_id();
 
-	if (!cpu_ops[cpu] || !cpu_ops[cpu]->cpu_stop)
+	if (!cpu_ops->cpu_stop)
 		return -EOPNOTSUPP;
 
-	if (cpu_ops[cpu]->cpu_disable)
-		ret = cpu_ops[cpu]->cpu_disable(cpu);
-
-	if (ret)
-		return ret;
-
 	remove_cpu_topology(cpu);
 	numa_remove_cpu(cpu);
 	set_cpu_online(cpu, false);
 	riscv_ipi_disable();
 	irq_migrate_all_off_this_cpu();
 
-	return ret;
+	return 0;
 }
 
 #ifdef CONFIG_HOTPLUG_CPU
@@ -62,8 +55,8 @@ void arch_cpuhp_cleanup_dead_cpu(unsigned int cpu)
 	pr_notice("CPU%u: off\n", cpu);
 
 	/* Verify from the firmware if the cpu is really stopped*/
-	if (cpu_ops[cpu]->cpu_is_stopped)
-		ret = cpu_ops[cpu]->cpu_is_stopped(cpu);
+	if (cpu_ops->cpu_is_stopped)
+		ret = cpu_ops->cpu_is_stopped(cpu);
 	if (ret)
 		pr_warn("CPU%d may not have stopped: %d\n", cpu, ret);
 }
@@ -77,7 +70,7 @@ void __noreturn arch_cpu_idle_dead(void)
 
 	cpuhp_ap_report_dead();
 
-	cpu_ops[smp_processor_id()]->cpu_stop();
+	cpu_ops->cpu_stop();
 	/* It should never reach here */
 	BUG();
 }

arch/riscv/kernel/cpu_ops.c

@@ -13,25 +13,21 @@
 #include <asm/sbi.h>
 #include <asm/smp.h>
 
-const struct cpu_operations *cpu_ops[NR_CPUS] __ro_after_init;
+const struct cpu_operations *cpu_ops __ro_after_init = &cpu_ops_spinwait;
 
 extern const struct cpu_operations cpu_ops_sbi;
 #ifndef CONFIG_RISCV_BOOT_SPINWAIT
 const struct cpu_operations cpu_ops_spinwait = {
-	.name		= "",
-	.cpu_prepare	= NULL,
 	.cpu_start	= NULL,
 };
 #endif
 
-void __init cpu_set_ops(int cpuid)
+void __init cpu_set_ops(void)
 {
 #if IS_ENABLED(CONFIG_RISCV_SBI)
 	if (sbi_probe_extension(SBI_EXT_HSM)) {
-		if (!cpuid)
-			pr_info("SBI HSM extension detected\n");
-		cpu_ops[cpuid] = &cpu_ops_sbi;
-	} else
+		pr_info("SBI HSM extension detected\n");
+		cpu_ops = &cpu_ops_sbi;
+	}
 #endif
-		cpu_ops[cpuid] = &cpu_ops_spinwait;
 }

arch/riscv/kernel/cpu_ops_sbi.c

@@ -79,23 +79,7 @@ static int sbi_cpu_start(unsigned int cpuid, struct task_struct *tidle)
 	return sbi_hsm_hart_start(hartid, boot_addr, hsm_data);
 }
 
-static int sbi_cpu_prepare(unsigned int cpuid)
-{
-	if (!cpu_ops_sbi.cpu_start) {
-		pr_err("cpu start method not defined for CPU [%d]\n", cpuid);
-		return -ENODEV;
-	}
-	return 0;
-}
-
 #ifdef CONFIG_HOTPLUG_CPU
-static int sbi_cpu_disable(unsigned int cpuid)
-{
-	if (!cpu_ops_sbi.cpu_stop)
-		return -EOPNOTSUPP;
-	return 0;
-}
-
 static void sbi_cpu_stop(void)
 {
 	int ret;
@@ -118,11 +102,8 @@ static int sbi_cpu_is_stopped(unsigned int cpuid)
 #endif
 
 const struct cpu_operations cpu_ops_sbi = {
-	.name		= "sbi",
-	.cpu_prepare	= sbi_cpu_prepare,
 	.cpu_start	= sbi_cpu_start,
 #ifdef CONFIG_HOTPLUG_CPU
-	.cpu_disable	= sbi_cpu_disable,
 	.cpu_stop	= sbi_cpu_stop,
 	.cpu_is_stopped	= sbi_cpu_is_stopped,
 #endif

arch/riscv/kernel/cpu_ops_spinwait.c

@@ -39,15 +39,6 @@ static void cpu_update_secondary_bootdata(unsigned int cpuid,
 	WRITE_ONCE(__cpu_spinwait_task_pointer[hartid], tidle);
 }
 
-static int spinwait_cpu_prepare(unsigned int cpuid)
-{
-	if (!cpu_ops_spinwait.cpu_start) {
-		pr_err("cpu start method not defined for CPU [%d]\n", cpuid);
-		return -ENODEV;
-	}
-	return 0;
-}
-
 static int spinwait_cpu_start(unsigned int cpuid, struct task_struct *tidle)
 {
 	/*
@@ -64,7 +55,5 @@ static int spinwait_cpu_start(unsigned int cpuid, struct task_struct *tidle)
 }
 
 const struct cpu_operations cpu_ops_spinwait = {
-	.name		= "spinwait",
-	.cpu_prepare	= spinwait_cpu_prepare,
 	.cpu_start	= spinwait_cpu_start,
 };

arch/riscv/kernel/head.S

@@ -11,7 +11,6 @@
 #include <asm/page.h>
 #include <asm/pgtable.h>
 #include <asm/csr.h>
-#include <asm/cpu_ops_sbi.h>
 #include <asm/hwcap.h>
 #include <asm/image.h>
 #include <asm/scs.h>

arch/riscv/kernel/setup.c

@@ -26,7 +26,6 @@
 #include <asm/alternative.h>
 #include <asm/cacheflush.h>
 #include <asm/cpufeature.h>
-#include <asm/cpu_ops.h>
 #include <asm/early_ioremap.h>
 #include <asm/pgtable.h>
 #include <asm/setup.h>

arch/riscv/kernel/smp.c

@@ -81,7 +81,7 @@ static inline void ipi_cpu_crash_stop(unsigned int cpu, struct pt_regs *regs)
 
 #ifdef CONFIG_HOTPLUG_CPU
 	if (cpu_has_hotplug(cpu))
-		cpu_ops[cpu]->cpu_stop();
+		cpu_ops->cpu_stop();
 #endif
 
 	for(;;)

arch/riscv/kernel/smpboot.c

@@ -49,7 +49,6 @@ void __init smp_prepare_boot_cpu(void)
 void __init smp_prepare_cpus(unsigned int max_cpus)
 {
 	int cpuid;
-	int ret;
 	unsigned int curr_cpuid;
 
 	init_cpu_topology();
@@ -66,11 +65,6 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
 	for_each_possible_cpu(cpuid) {
 		if (cpuid == curr_cpuid)
 			continue;
-		if (cpu_ops[cpuid]->cpu_prepare) {
-			ret = cpu_ops[cpuid]->cpu_prepare(cpuid);
-			if (ret)
-				continue;
-		}
 		set_cpu_present(cpuid, true);
 		numa_store_cpu_info(cpuid);
 	}
@@ -125,18 +119,7 @@ static int __init acpi_parse_rintc(union acpi_subtable_headers *header, const un
 
 static void __init acpi_parse_and_init_cpus(void)
 {
-	int cpuid;
-
-	cpu_set_ops(0);
-
 	acpi_table_parse_madt(ACPI_MADT_TYPE_RINTC, acpi_parse_rintc, 0);
-
-	for (cpuid = 1; cpuid < nr_cpu_ids; cpuid++) {
-		if (cpuid_to_hartid_map(cpuid) != INVALID_HARTID) {
-			cpu_set_ops(cpuid);
-			set_cpu_possible(cpuid, true);
-		}
-	}
 }
 #else
 #define acpi_parse_and_init_cpus(...)	do { } while (0)
@@ -150,8 +133,6 @@ static void __init of_parse_and_init_cpus(void)
 	int cpuid = 1;
 	int rc;
 
-	cpu_set_ops(0);
-
 	for_each_of_cpu_node(dn) {
 		rc = riscv_early_of_processor_hartid(dn, &hart);
 		if (rc < 0)
@@ -179,27 +160,28 @@ static void __init of_parse_and_init_cpus(void)
 	if (cpuid > nr_cpu_ids)
 		pr_warn("Total number of cpus [%d] is greater than nr_cpus option value [%d]\n",
 			cpuid, nr_cpu_ids);
-
-	for (cpuid = 1; cpuid < nr_cpu_ids; cpuid++) {
-		if (cpuid_to_hartid_map(cpuid) != INVALID_HARTID) {
-			cpu_set_ops(cpuid);
-			set_cpu_possible(cpuid, true);
-		}
-	}
 }
 
 void __init setup_smp(void)
 {
+	int cpuid;
+
+	cpu_set_ops();
+
 	if (acpi_disabled)
 		of_parse_and_init_cpus();
 	else
 		acpi_parse_and_init_cpus();
+
+	for (cpuid = 1; cpuid < nr_cpu_ids; cpuid++)
+		if (cpuid_to_hartid_map(cpuid) != INVALID_HARTID)
+			set_cpu_possible(cpuid, true);
 }
 
 static int start_secondary_cpu(int cpu, struct task_struct *tidle)
 {
-	if (cpu_ops[cpu]->cpu_start)
-		return cpu_ops[cpu]->cpu_start(cpu, tidle);
+	if (cpu_ops->cpu_start)
+		return cpu_ops->cpu_start(cpu, tidle);
 
 	return -EOPNOTSUPP;
 }