x86/smpboot: Switch to hotplug core state synchronization

The new AP state tracking and synchronization mechanism in the CPU hotplug
core code allows to remove quite some x86 specific code:

  1) The AP alive synchronization based on cpumasks

  2) The decision whether an AP can be brought up again

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Tested-by: Helge Deller <deller@gmx.de> # parisc
Tested-by: Guilherme G. Piccoli <gpiccoli@igalia.com> # Steam Deck
Link: https://lore.kernel.org/r/20230512205256.529657366@linutronix.de

2 files changed, 29 insertions, 26 deletions

diff --git a/arch/x86/xen/smp_hvm.c b/arch/x86/xen/smp_hvm.c
index b70afdff419c..ac95d1981cc0 100644
--- a/arch/x86/xen/smp_hvm.c
+++ b/arch/x86/xen/smp_hvm.c
@@ -55,18 +55,16 @@ static void __init xen_hvm_smp_prepare_cpus(unsigned int max_cpus)
 }
 
 #ifdef CONFIG_HOTPLUG_CPU
-static void xen_hvm_cpu_die(unsigned int cpu)
+static void xen_hvm_cleanup_dead_cpu(unsigned int cpu)
 {
-	if (common_cpu_die(cpu) == 0) {
-		if (xen_have_vector_callback) {
-			xen_smp_intr_free(cpu);
-			xen_uninit_lock_cpu(cpu);
-			xen_teardown_timer(cpu);
-		}
+	if (xen_have_vector_callback) {
+		xen_smp_intr_free(cpu);
+		xen_uninit_lock_cpu(cpu);
+		xen_teardown_timer(cpu);
 	}
 }
 #else
-static void xen_hvm_cpu_die(unsigned int cpu)
+static void xen_hvm_cleanup_dead_cpu(unsigned int cpu)
 {
 	BUG();
 }
@@ -77,7 +75,7 @@ void __init xen_hvm_smp_init(void)
 	smp_ops.smp_prepare_boot_cpu = xen_hvm_smp_prepare_boot_cpu;
 	smp_ops.smp_prepare_cpus = xen_hvm_smp_prepare_cpus;
 	smp_ops.smp_cpus_done = xen_smp_cpus_done;
-	smp_ops.cpu_die = xen_hvm_cpu_die;
+	smp_ops.cleanup_dead_cpu = xen_hvm_cleanup_dead_cpu;
 
 	if (!xen_have_vector_callback) {
 #ifdef CONFIG_PARAVIRT_SPINLOCKS
diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c
index be40927667cf..b089fb1cefc6 100644
--- a/arch/x86/xen/smp_pv.c
+++ b/arch/x86/xen/smp_pv.c
@@ -62,6 +62,7 @@ static void cpu_bringup(void)
 	int cpu;
 
 	cr4_init();
+	cpuhp_ap_sync_alive();
 	cpu_init();
 	touch_softlockup_watchdog();
 
@@ -83,7 +84,7 @@ static void cpu_bringup(void)
 
 	set_cpu_online(cpu, true);
 
-	cpu_set_state_online(cpu);  /* Implies full memory barrier. */
+	smp_mb();
 
 	/* We can take interrupts now: we're officially "up". */
 	local_irq_enable();
@@ -323,14 +324,6 @@ static int xen_pv_cpu_up(unsigned int cpu, struct task_struct *idle)
 
 	xen_setup_runstate_info(cpu);
 
-	/*
-	 * PV VCPUs are always successfully taken down (see 'while' loop
-	 * in xen_cpu_die()), so -EBUSY is an error.
-	 */
-	rc = cpu_check_up_prepare(cpu);
-	if (rc)
-		return rc;
-
 	/* make sure interrupts start blocked */
 	per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
 
@@ -349,6 +342,11 @@ static int xen_pv_cpu_up(unsigned int cpu, struct task_struct *idle)
 	return 0;
 }
 
+static void xen_pv_poll_sync_state(void)
+{
+	HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
+}
+
 #ifdef CONFIG_HOTPLUG_CPU
 static int xen_pv_cpu_disable(void)
 {
@@ -364,18 +362,18 @@ static int xen_pv_cpu_disable(void)
 
 static void xen_pv_cpu_die(unsigned int cpu)
 {
-	while (HYPERVISOR_vcpu_op(VCPUOP_is_up,
-				  xen_vcpu_nr(cpu), NULL)) {
+	while (HYPERVISOR_vcpu_op(VCPUOP_is_up, xen_vcpu_nr(cpu), NULL)) {
 		__set_current_state(TASK_UNINTERRUPTIBLE);
 		schedule_timeout(HZ/10);
 	}
+}
 
-	if (common_cpu_die(cpu) == 0) {
-		xen_smp_intr_free(cpu);
-		xen_uninit_lock_cpu(cpu);
-		xen_teardown_timer(cpu);
-		xen_pmu_finish(cpu);
-	}
+static void xen_pv_cleanup_dead_cpu(unsigned int cpu)
+{
+	xen_smp_intr_free(cpu);
+	xen_uninit_lock_cpu(cpu);
+	xen_teardown_timer(cpu);
+	xen_pmu_finish(cpu);
 }
 
 static void __noreturn xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */
@@ -397,6 +395,11 @@ static void xen_pv_cpu_die(unsigned int cpu)
 	BUG();
 }
 
+static void xen_pv_cleanup_dead_cpu(unsigned int cpu)
+{
+	BUG();
+}
+
 static void __noreturn xen_pv_play_dead(void)
 {
 	BUG();
@@ -437,6 +440,8 @@ static const struct smp_ops xen_smp_ops __initconst = {
 
 	.cpu_up = xen_pv_cpu_up,
 	.cpu_die = xen_pv_cpu_die,
+	.cleanup_dead_cpu = xen_pv_cleanup_dead_cpu,
+	.poll_sync_state = xen_pv_poll_sync_state,
 	.cpu_disable = xen_pv_cpu_disable,
 	.play_dead = xen_pv_play_dead,