diff options
Diffstat (limited to 'arch/s390/kernel/wti.c')
| -rw-r--r-- | arch/s390/kernel/wti.c | 215 |
1 files changed, 215 insertions, 0 deletions
diff --git a/arch/s390/kernel/wti.c b/arch/s390/kernel/wti.c new file mode 100644 index 000000000000..949fdbf0e8b6 --- /dev/null +++ b/arch/s390/kernel/wti.c @@ -0,0 +1,215 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Support for warning track interruption + * + * Copyright IBM Corp. 2023 + */ + +#include <linux/cpu.h> +#include <linux/debugfs.h> +#include <linux/kallsyms.h> +#include <linux/smpboot.h> +#include <linux/irq.h> +#include <uapi/linux/sched/types.h> +#include <asm/debug.h> +#include <asm/diag.h> +#include <asm/sclp.h> + +#define WTI_DBF_LEN 64 + +struct wti_debug { + unsigned long missed; + unsigned long addr; + pid_t pid; +}; + +struct wti_state { + /* debug data for s390dbf */ + struct wti_debug dbg; + /* + * Represents the real-time thread responsible to + * acknowledge the warning-track interrupt and trigger + * preliminary and postliminary precautions. + */ + struct task_struct *thread; + /* + * If pending is true, the real-time thread must be scheduled. + * If not, a wake up of that thread will remain a noop. + */ + bool pending; +}; + +static DEFINE_PER_CPU(struct wti_state, wti_state); + +static debug_info_t *wti_dbg; + +/* + * During a warning-track grace period, interrupts are disabled + * to prevent delays of the warning-track acknowledgment. + * + * Once the CPU is physically dispatched again, interrupts are + * re-enabled. + */ + +static void wti_irq_disable(void) +{ + unsigned long flags; + struct ctlreg cr6; + + local_irq_save(flags); + local_ctl_store(6, &cr6); + /* disable all I/O interrupts */ + cr6.val &= ~0xff000000UL; + local_ctl_load(6, &cr6); + local_irq_restore(flags); +} + +static void wti_irq_enable(void) +{ + unsigned long flags; + struct ctlreg cr6; + + local_irq_save(flags); + local_ctl_store(6, &cr6); + /* enable all I/O interrupts */ + cr6.val |= 0xff000000UL; + local_ctl_load(6, &cr6); + local_irq_restore(flags); +} + +static void store_debug_data(struct wti_state *st) +{ + struct pt_regs *regs = get_irq_regs(); + + st->dbg.pid = current->pid; + st->dbg.addr = 0; + if (!user_mode(regs)) + st->dbg.addr = regs->psw.addr; +} + +static void wti_interrupt(struct ext_code ext_code, + unsigned int param32, unsigned long param64) +{ + struct wti_state *st = this_cpu_ptr(&wti_state); + + inc_irq_stat(IRQEXT_WTI); + wti_irq_disable(); + store_debug_data(st); + st->pending = true; + wake_up_process(st->thread); +} + +static int wti_pending(unsigned int cpu) +{ + struct wti_state *st = per_cpu_ptr(&wti_state, cpu); + + return st->pending; +} + +static void wti_dbf_grace_period(struct wti_state *st) +{ + struct wti_debug *wdi = &st->dbg; + char buf[WTI_DBF_LEN]; + + if (wdi->addr) + snprintf(buf, sizeof(buf), "%d %pS", wdi->pid, (void *)wdi->addr); + else + snprintf(buf, sizeof(buf), "%d <user>", wdi->pid); + debug_text_event(wti_dbg, 2, buf); + wdi->missed++; +} + +static int wti_show(struct seq_file *seq, void *v) +{ + struct wti_state *st; + int cpu; + + cpus_read_lock(); + seq_puts(seq, " "); + for_each_online_cpu(cpu) + seq_printf(seq, "CPU%-8d", cpu); + seq_putc(seq, '\n'); + for_each_online_cpu(cpu) { + st = per_cpu_ptr(&wti_state, cpu); + seq_printf(seq, " %10lu", st->dbg.missed); + } + seq_putc(seq, '\n'); + cpus_read_unlock(); + return 0; +} +DEFINE_SHOW_ATTRIBUTE(wti); + +static void wti_thread_fn(unsigned int cpu) +{ + struct wti_state *st = per_cpu_ptr(&wti_state, cpu); + + st->pending = false; + /* + * Yield CPU voluntarily to the hypervisor. Control + * resumes when hypervisor decides to dispatch CPU + * to this LPAR again. + */ + if (diag49c(DIAG49C_SUBC_ACK)) + wti_dbf_grace_period(st); + wti_irq_enable(); +} + +static struct smp_hotplug_thread wti_threads = { + .store = &wti_state.thread, + .thread_should_run = wti_pending, + .thread_fn = wti_thread_fn, + .thread_comm = "cpuwti/%u", + .selfparking = false, +}; + +static int __init wti_init(void) +{ + struct sched_param wti_sched_param = { .sched_priority = MAX_RT_PRIO - 1 }; + struct dentry *wti_dir; + struct wti_state *st; + int cpu, rc; + + rc = -EOPNOTSUPP; + if (!sclp.has_wti) + goto out; + rc = smpboot_register_percpu_thread(&wti_threads); + if (WARN_ON(rc)) + goto out; + for_each_online_cpu(cpu) { + st = per_cpu_ptr(&wti_state, cpu); + sched_setscheduler(st->thread, SCHED_FIFO, &wti_sched_param); + } + rc = register_external_irq(EXT_IRQ_WARNING_TRACK, wti_interrupt); + if (rc) { + pr_warn("Couldn't request external interrupt 0x1007\n"); + goto out_thread; + } + irq_subclass_register(IRQ_SUBCLASS_WARNING_TRACK); + rc = diag49c(DIAG49C_SUBC_REG); + if (rc) { + pr_warn("Failed to register warning track interrupt through DIAG 49C\n"); + rc = -EOPNOTSUPP; + goto out_subclass; + } + wti_dir = debugfs_create_dir("wti", arch_debugfs_dir); + debugfs_create_file("stat", 0400, wti_dir, NULL, &wti_fops); + wti_dbg = debug_register("wti", 1, 1, WTI_DBF_LEN); + if (!wti_dbg) { + rc = -ENOMEM; + goto out_debug_register; + } + rc = debug_register_view(wti_dbg, &debug_hex_ascii_view); + if (rc) + goto out_debug_register; + goto out; +out_debug_register: + debug_unregister(wti_dbg); +out_subclass: + irq_subclass_unregister(IRQ_SUBCLASS_WARNING_TRACK); + unregister_external_irq(EXT_IRQ_WARNING_TRACK, wti_interrupt); +out_thread: + smpboot_unregister_percpu_thread(&wti_threads); +out: + return rc; +} +late_initcall(wti_init); |