884 строки
20 KiB
C
884 строки
20 KiB
C
/*
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* KVM paravirt_ops implementation
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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* Copyright (C) 2007, Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
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* Copyright IBM Corporation, 2007
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* Authors: Anthony Liguori <aliguori@us.ibm.com>
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*/
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#include <linux/context_tracking.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/kvm_para.h>
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#include <linux/cpu.h>
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#include <linux/mm.h>
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#include <linux/highmem.h>
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#include <linux/hardirq.h>
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#include <linux/notifier.h>
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#include <linux/reboot.h>
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#include <linux/hash.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <linux/kprobes.h>
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#include <linux/debugfs.h>
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#include <linux/nmi.h>
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#include <linux/swait.h>
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#include <asm/timer.h>
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#include <asm/cpu.h>
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#include <asm/traps.h>
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#include <asm/desc.h>
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#include <asm/tlbflush.h>
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#include <asm/idle.h>
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#include <asm/apic.h>
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#include <asm/apicdef.h>
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#include <asm/hypervisor.h>
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#include <asm/kvm_guest.h>
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static int kvmapf = 1;
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static int parse_no_kvmapf(char *arg)
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{
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kvmapf = 0;
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return 0;
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}
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early_param("no-kvmapf", parse_no_kvmapf);
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static int steal_acc = 1;
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static int parse_no_stealacc(char *arg)
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{
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steal_acc = 0;
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return 0;
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}
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early_param("no-steal-acc", parse_no_stealacc);
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static int kvmclock_vsyscall = 1;
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static int parse_no_kvmclock_vsyscall(char *arg)
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{
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kvmclock_vsyscall = 0;
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return 0;
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}
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early_param("no-kvmclock-vsyscall", parse_no_kvmclock_vsyscall);
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static DEFINE_PER_CPU(struct kvm_vcpu_pv_apf_data, apf_reason) __aligned(64);
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static DEFINE_PER_CPU(struct kvm_steal_time, steal_time) __aligned(64);
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static int has_steal_clock = 0;
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/*
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* No need for any "IO delay" on KVM
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*/
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static void kvm_io_delay(void)
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{
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}
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#define KVM_TASK_SLEEP_HASHBITS 8
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#define KVM_TASK_SLEEP_HASHSIZE (1<<KVM_TASK_SLEEP_HASHBITS)
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struct kvm_task_sleep_node {
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struct hlist_node link;
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struct swait_queue_head wq;
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u32 token;
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int cpu;
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bool halted;
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};
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static struct kvm_task_sleep_head {
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raw_spinlock_t lock;
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struct hlist_head list;
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} async_pf_sleepers[KVM_TASK_SLEEP_HASHSIZE];
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static struct kvm_task_sleep_node *_find_apf_task(struct kvm_task_sleep_head *b,
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u32 token)
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{
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struct hlist_node *p;
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hlist_for_each(p, &b->list) {
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struct kvm_task_sleep_node *n =
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hlist_entry(p, typeof(*n), link);
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if (n->token == token)
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return n;
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}
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return NULL;
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}
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void kvm_async_pf_task_wait(u32 token)
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{
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u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS);
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struct kvm_task_sleep_head *b = &async_pf_sleepers[key];
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struct kvm_task_sleep_node n, *e;
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DECLARE_SWAITQUEUE(wait);
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rcu_irq_enter();
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raw_spin_lock(&b->lock);
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e = _find_apf_task(b, token);
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if (e) {
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/* dummy entry exist -> wake up was delivered ahead of PF */
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hlist_del(&e->link);
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kfree(e);
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raw_spin_unlock(&b->lock);
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rcu_irq_exit();
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return;
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}
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n.token = token;
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n.cpu = smp_processor_id();
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n.halted = is_idle_task(current) || preempt_count() > 1;
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init_swait_queue_head(&n.wq);
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hlist_add_head(&n.link, &b->list);
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raw_spin_unlock(&b->lock);
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for (;;) {
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if (!n.halted)
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prepare_to_swait(&n.wq, &wait, TASK_UNINTERRUPTIBLE);
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if (hlist_unhashed(&n.link))
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break;
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if (!n.halted) {
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local_irq_enable();
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schedule();
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local_irq_disable();
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} else {
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/*
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* We cannot reschedule. So halt.
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*/
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rcu_irq_exit();
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native_safe_halt();
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rcu_irq_enter();
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local_irq_disable();
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}
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}
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if (!n.halted)
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finish_swait(&n.wq, &wait);
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rcu_irq_exit();
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return;
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}
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EXPORT_SYMBOL_GPL(kvm_async_pf_task_wait);
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static void apf_task_wake_one(struct kvm_task_sleep_node *n)
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{
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hlist_del_init(&n->link);
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if (n->halted)
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smp_send_reschedule(n->cpu);
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else if (swait_active(&n->wq))
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swake_up(&n->wq);
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}
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static void apf_task_wake_all(void)
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{
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int i;
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for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++) {
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struct hlist_node *p, *next;
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struct kvm_task_sleep_head *b = &async_pf_sleepers[i];
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raw_spin_lock(&b->lock);
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hlist_for_each_safe(p, next, &b->list) {
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struct kvm_task_sleep_node *n =
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hlist_entry(p, typeof(*n), link);
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if (n->cpu == smp_processor_id())
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apf_task_wake_one(n);
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}
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raw_spin_unlock(&b->lock);
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}
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}
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void kvm_async_pf_task_wake(u32 token)
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{
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u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS);
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struct kvm_task_sleep_head *b = &async_pf_sleepers[key];
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struct kvm_task_sleep_node *n;
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if (token == ~0) {
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apf_task_wake_all();
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return;
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}
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again:
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raw_spin_lock(&b->lock);
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n = _find_apf_task(b, token);
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if (!n) {
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/*
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* async PF was not yet handled.
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* Add dummy entry for the token.
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*/
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n = kzalloc(sizeof(*n), GFP_ATOMIC);
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if (!n) {
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/*
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* Allocation failed! Busy wait while other cpu
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* handles async PF.
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*/
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raw_spin_unlock(&b->lock);
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cpu_relax();
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goto again;
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}
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n->token = token;
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n->cpu = smp_processor_id();
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init_swait_queue_head(&n->wq);
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hlist_add_head(&n->link, &b->list);
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} else
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apf_task_wake_one(n);
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raw_spin_unlock(&b->lock);
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return;
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}
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EXPORT_SYMBOL_GPL(kvm_async_pf_task_wake);
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u32 kvm_read_and_reset_pf_reason(void)
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{
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u32 reason = 0;
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if (__this_cpu_read(apf_reason.enabled)) {
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reason = __this_cpu_read(apf_reason.reason);
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__this_cpu_write(apf_reason.reason, 0);
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}
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return reason;
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}
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EXPORT_SYMBOL_GPL(kvm_read_and_reset_pf_reason);
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NOKPROBE_SYMBOL(kvm_read_and_reset_pf_reason);
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dotraplinkage void
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do_async_page_fault(struct pt_regs *regs, unsigned long error_code)
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{
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enum ctx_state prev_state;
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switch (kvm_read_and_reset_pf_reason()) {
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default:
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trace_do_page_fault(regs, error_code);
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break;
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case KVM_PV_REASON_PAGE_NOT_PRESENT:
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/* page is swapped out by the host. */
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prev_state = exception_enter();
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exit_idle();
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kvm_async_pf_task_wait((u32)read_cr2());
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exception_exit(prev_state);
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break;
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case KVM_PV_REASON_PAGE_READY:
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rcu_irq_enter();
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exit_idle();
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kvm_async_pf_task_wake((u32)read_cr2());
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rcu_irq_exit();
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break;
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}
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}
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NOKPROBE_SYMBOL(do_async_page_fault);
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static void __init paravirt_ops_setup(void)
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{
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pv_info.name = "KVM";
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if (kvm_para_has_feature(KVM_FEATURE_NOP_IO_DELAY))
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pv_cpu_ops.io_delay = kvm_io_delay;
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#ifdef CONFIG_X86_IO_APIC
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no_timer_check = 1;
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#endif
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}
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static void kvm_register_steal_time(void)
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{
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int cpu = smp_processor_id();
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struct kvm_steal_time *st = &per_cpu(steal_time, cpu);
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if (!has_steal_clock)
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return;
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wrmsrl(MSR_KVM_STEAL_TIME, (slow_virt_to_phys(st) | KVM_MSR_ENABLED));
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pr_info("kvm-stealtime: cpu %d, msr %llx\n",
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cpu, (unsigned long long) slow_virt_to_phys(st));
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}
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static DEFINE_PER_CPU(unsigned long, kvm_apic_eoi) = KVM_PV_EOI_DISABLED;
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static void kvm_guest_apic_eoi_write(u32 reg, u32 val)
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{
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/**
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* This relies on __test_and_clear_bit to modify the memory
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* in a way that is atomic with respect to the local CPU.
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* The hypervisor only accesses this memory from the local CPU so
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* there's no need for lock or memory barriers.
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* An optimization barrier is implied in apic write.
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*/
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if (__test_and_clear_bit(KVM_PV_EOI_BIT, this_cpu_ptr(&kvm_apic_eoi)))
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return;
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apic_write(APIC_EOI, APIC_EOI_ACK);
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}
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static void kvm_guest_cpu_init(void)
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{
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if (!kvm_para_available())
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return;
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if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF) && kvmapf) {
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u64 pa = slow_virt_to_phys(this_cpu_ptr(&apf_reason));
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#ifdef CONFIG_PREEMPT
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pa |= KVM_ASYNC_PF_SEND_ALWAYS;
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#endif
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wrmsrl(MSR_KVM_ASYNC_PF_EN, pa | KVM_ASYNC_PF_ENABLED);
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__this_cpu_write(apf_reason.enabled, 1);
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printk(KERN_INFO"KVM setup async PF for cpu %d\n",
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smp_processor_id());
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}
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if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) {
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unsigned long pa;
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/* Size alignment is implied but just to make it explicit. */
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BUILD_BUG_ON(__alignof__(kvm_apic_eoi) < 4);
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__this_cpu_write(kvm_apic_eoi, 0);
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pa = slow_virt_to_phys(this_cpu_ptr(&kvm_apic_eoi))
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| KVM_MSR_ENABLED;
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wrmsrl(MSR_KVM_PV_EOI_EN, pa);
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}
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if (has_steal_clock)
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kvm_register_steal_time();
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}
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static void kvm_pv_disable_apf(void)
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{
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if (!__this_cpu_read(apf_reason.enabled))
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return;
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wrmsrl(MSR_KVM_ASYNC_PF_EN, 0);
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__this_cpu_write(apf_reason.enabled, 0);
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printk(KERN_INFO"Unregister pv shared memory for cpu %d\n",
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smp_processor_id());
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}
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static void kvm_pv_guest_cpu_reboot(void *unused)
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{
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/*
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* We disable PV EOI before we load a new kernel by kexec,
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* since MSR_KVM_PV_EOI_EN stores a pointer into old kernel's memory.
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* New kernel can re-enable when it boots.
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*/
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if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
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wrmsrl(MSR_KVM_PV_EOI_EN, 0);
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kvm_pv_disable_apf();
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kvm_disable_steal_time();
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}
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static int kvm_pv_reboot_notify(struct notifier_block *nb,
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unsigned long code, void *unused)
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{
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if (code == SYS_RESTART)
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on_each_cpu(kvm_pv_guest_cpu_reboot, NULL, 1);
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return NOTIFY_DONE;
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}
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static struct notifier_block kvm_pv_reboot_nb = {
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.notifier_call = kvm_pv_reboot_notify,
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};
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static u64 kvm_steal_clock(int cpu)
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{
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u64 steal;
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struct kvm_steal_time *src;
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int version;
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src = &per_cpu(steal_time, cpu);
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do {
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version = src->version;
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rmb();
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steal = src->steal;
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rmb();
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} while ((version & 1) || (version != src->version));
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return steal;
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}
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void kvm_disable_steal_time(void)
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{
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if (!has_steal_clock)
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return;
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wrmsr(MSR_KVM_STEAL_TIME, 0, 0);
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}
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#ifdef CONFIG_SMP
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static void __init kvm_smp_prepare_boot_cpu(void)
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{
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kvm_guest_cpu_init();
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native_smp_prepare_boot_cpu();
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kvm_spinlock_init();
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}
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static void kvm_guest_cpu_online(void *dummy)
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{
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kvm_guest_cpu_init();
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}
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static void kvm_guest_cpu_offline(void *dummy)
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{
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kvm_disable_steal_time();
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if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
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wrmsrl(MSR_KVM_PV_EOI_EN, 0);
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kvm_pv_disable_apf();
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apf_task_wake_all();
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}
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static int kvm_cpu_notify(struct notifier_block *self, unsigned long action,
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void *hcpu)
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{
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int cpu = (unsigned long)hcpu;
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switch (action) {
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case CPU_ONLINE:
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case CPU_DOWN_FAILED:
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case CPU_ONLINE_FROZEN:
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smp_call_function_single(cpu, kvm_guest_cpu_online, NULL, 0);
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break;
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case CPU_DOWN_PREPARE:
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case CPU_DOWN_PREPARE_FROZEN:
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smp_call_function_single(cpu, kvm_guest_cpu_offline, NULL, 1);
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break;
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default:
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break;
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}
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return NOTIFY_OK;
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}
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static struct notifier_block kvm_cpu_notifier = {
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.notifier_call = kvm_cpu_notify,
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};
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#endif
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static void __init kvm_apf_trap_init(void)
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{
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set_intr_gate(14, async_page_fault);
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}
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void __init kvm_guest_init(void)
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{
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int i;
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if (!kvm_para_available())
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return;
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paravirt_ops_setup();
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register_reboot_notifier(&kvm_pv_reboot_nb);
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for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++)
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raw_spin_lock_init(&async_pf_sleepers[i].lock);
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if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF))
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x86_init.irqs.trap_init = kvm_apf_trap_init;
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if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
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has_steal_clock = 1;
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pv_time_ops.steal_clock = kvm_steal_clock;
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}
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if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
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apic_set_eoi_write(kvm_guest_apic_eoi_write);
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if (kvmclock_vsyscall)
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kvm_setup_vsyscall_timeinfo();
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#ifdef CONFIG_SMP
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smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
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register_cpu_notifier(&kvm_cpu_notifier);
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#else
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kvm_guest_cpu_init();
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#endif
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/*
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* Hard lockup detection is enabled by default. Disable it, as guests
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* can get false positives too easily, for example if the host is
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* overcommitted.
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*/
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hardlockup_detector_disable();
|
|
}
|
|
|
|
static noinline uint32_t __kvm_cpuid_base(void)
|
|
{
|
|
if (boot_cpu_data.cpuid_level < 0)
|
|
return 0; /* So we don't blow up on old processors */
|
|
|
|
if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
|
|
return hypervisor_cpuid_base("KVMKVMKVM\0\0\0", 0);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static inline uint32_t kvm_cpuid_base(void)
|
|
{
|
|
static int kvm_cpuid_base = -1;
|
|
|
|
if (kvm_cpuid_base == -1)
|
|
kvm_cpuid_base = __kvm_cpuid_base();
|
|
|
|
return kvm_cpuid_base;
|
|
}
|
|
|
|
bool kvm_para_available(void)
|
|
{
|
|
return kvm_cpuid_base() != 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(kvm_para_available);
|
|
|
|
unsigned int kvm_arch_para_features(void)
|
|
{
|
|
return cpuid_eax(kvm_cpuid_base() | KVM_CPUID_FEATURES);
|
|
}
|
|
|
|
static uint32_t __init kvm_detect(void)
|
|
{
|
|
return kvm_cpuid_base();
|
|
}
|
|
|
|
const struct hypervisor_x86 x86_hyper_kvm __refconst = {
|
|
.name = "KVM",
|
|
.detect = kvm_detect,
|
|
.x2apic_available = kvm_para_available,
|
|
};
|
|
EXPORT_SYMBOL_GPL(x86_hyper_kvm);
|
|
|
|
static __init int activate_jump_labels(void)
|
|
{
|
|
if (has_steal_clock) {
|
|
static_key_slow_inc(¶virt_steal_enabled);
|
|
if (steal_acc)
|
|
static_key_slow_inc(¶virt_steal_rq_enabled);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
arch_initcall(activate_jump_labels);
|
|
|
|
#ifdef CONFIG_PARAVIRT_SPINLOCKS
|
|
|
|
/* Kick a cpu by its apicid. Used to wake up a halted vcpu */
|
|
static void kvm_kick_cpu(int cpu)
|
|
{
|
|
int apicid;
|
|
unsigned long flags = 0;
|
|
|
|
apicid = per_cpu(x86_cpu_to_apicid, cpu);
|
|
kvm_hypercall2(KVM_HC_KICK_CPU, flags, apicid);
|
|
}
|
|
|
|
|
|
#ifdef CONFIG_QUEUED_SPINLOCKS
|
|
|
|
#include <asm/qspinlock.h>
|
|
|
|
static void kvm_wait(u8 *ptr, u8 val)
|
|
{
|
|
unsigned long flags;
|
|
|
|
if (in_nmi())
|
|
return;
|
|
|
|
local_irq_save(flags);
|
|
|
|
if (READ_ONCE(*ptr) != val)
|
|
goto out;
|
|
|
|
/*
|
|
* halt until it's our turn and kicked. Note that we do safe halt
|
|
* for irq enabled case to avoid hang when lock info is overwritten
|
|
* in irq spinlock slowpath and no spurious interrupt occur to save us.
|
|
*/
|
|
if (arch_irqs_disabled_flags(flags))
|
|
halt();
|
|
else
|
|
safe_halt();
|
|
|
|
out:
|
|
local_irq_restore(flags);
|
|
}
|
|
|
|
#else /* !CONFIG_QUEUED_SPINLOCKS */
|
|
|
|
enum kvm_contention_stat {
|
|
TAKEN_SLOW,
|
|
TAKEN_SLOW_PICKUP,
|
|
RELEASED_SLOW,
|
|
RELEASED_SLOW_KICKED,
|
|
NR_CONTENTION_STATS
|
|
};
|
|
|
|
#ifdef CONFIG_KVM_DEBUG_FS
|
|
#define HISTO_BUCKETS 30
|
|
|
|
static struct kvm_spinlock_stats
|
|
{
|
|
u32 contention_stats[NR_CONTENTION_STATS];
|
|
u32 histo_spin_blocked[HISTO_BUCKETS+1];
|
|
u64 time_blocked;
|
|
} spinlock_stats;
|
|
|
|
static u8 zero_stats;
|
|
|
|
static inline void check_zero(void)
|
|
{
|
|
u8 ret;
|
|
u8 old;
|
|
|
|
old = READ_ONCE(zero_stats);
|
|
if (unlikely(old)) {
|
|
ret = cmpxchg(&zero_stats, old, 0);
|
|
/* This ensures only one fellow resets the stat */
|
|
if (ret == old)
|
|
memset(&spinlock_stats, 0, sizeof(spinlock_stats));
|
|
}
|
|
}
|
|
|
|
static inline void add_stats(enum kvm_contention_stat var, u32 val)
|
|
{
|
|
check_zero();
|
|
spinlock_stats.contention_stats[var] += val;
|
|
}
|
|
|
|
|
|
static inline u64 spin_time_start(void)
|
|
{
|
|
return sched_clock();
|
|
}
|
|
|
|
static void __spin_time_accum(u64 delta, u32 *array)
|
|
{
|
|
unsigned index;
|
|
|
|
index = ilog2(delta);
|
|
check_zero();
|
|
|
|
if (index < HISTO_BUCKETS)
|
|
array[index]++;
|
|
else
|
|
array[HISTO_BUCKETS]++;
|
|
}
|
|
|
|
static inline void spin_time_accum_blocked(u64 start)
|
|
{
|
|
u32 delta;
|
|
|
|
delta = sched_clock() - start;
|
|
__spin_time_accum(delta, spinlock_stats.histo_spin_blocked);
|
|
spinlock_stats.time_blocked += delta;
|
|
}
|
|
|
|
static struct dentry *d_spin_debug;
|
|
static struct dentry *d_kvm_debug;
|
|
|
|
static struct dentry *kvm_init_debugfs(void)
|
|
{
|
|
d_kvm_debug = debugfs_create_dir("kvm-guest", NULL);
|
|
if (!d_kvm_debug)
|
|
printk(KERN_WARNING "Could not create 'kvm' debugfs directory\n");
|
|
|
|
return d_kvm_debug;
|
|
}
|
|
|
|
static int __init kvm_spinlock_debugfs(void)
|
|
{
|
|
struct dentry *d_kvm;
|
|
|
|
d_kvm = kvm_init_debugfs();
|
|
if (d_kvm == NULL)
|
|
return -ENOMEM;
|
|
|
|
d_spin_debug = debugfs_create_dir("spinlocks", d_kvm);
|
|
|
|
debugfs_create_u8("zero_stats", 0644, d_spin_debug, &zero_stats);
|
|
|
|
debugfs_create_u32("taken_slow", 0444, d_spin_debug,
|
|
&spinlock_stats.contention_stats[TAKEN_SLOW]);
|
|
debugfs_create_u32("taken_slow_pickup", 0444, d_spin_debug,
|
|
&spinlock_stats.contention_stats[TAKEN_SLOW_PICKUP]);
|
|
|
|
debugfs_create_u32("released_slow", 0444, d_spin_debug,
|
|
&spinlock_stats.contention_stats[RELEASED_SLOW]);
|
|
debugfs_create_u32("released_slow_kicked", 0444, d_spin_debug,
|
|
&spinlock_stats.contention_stats[RELEASED_SLOW_KICKED]);
|
|
|
|
debugfs_create_u64("time_blocked", 0444, d_spin_debug,
|
|
&spinlock_stats.time_blocked);
|
|
|
|
debugfs_create_u32_array("histo_blocked", 0444, d_spin_debug,
|
|
spinlock_stats.histo_spin_blocked, HISTO_BUCKETS + 1);
|
|
|
|
return 0;
|
|
}
|
|
fs_initcall(kvm_spinlock_debugfs);
|
|
#else /* !CONFIG_KVM_DEBUG_FS */
|
|
static inline void add_stats(enum kvm_contention_stat var, u32 val)
|
|
{
|
|
}
|
|
|
|
static inline u64 spin_time_start(void)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
static inline void spin_time_accum_blocked(u64 start)
|
|
{
|
|
}
|
|
#endif /* CONFIG_KVM_DEBUG_FS */
|
|
|
|
struct kvm_lock_waiting {
|
|
struct arch_spinlock *lock;
|
|
__ticket_t want;
|
|
};
|
|
|
|
/* cpus 'waiting' on a spinlock to become available */
|
|
static cpumask_t waiting_cpus;
|
|
|
|
/* Track spinlock on which a cpu is waiting */
|
|
static DEFINE_PER_CPU(struct kvm_lock_waiting, klock_waiting);
|
|
|
|
__visible void kvm_lock_spinning(struct arch_spinlock *lock, __ticket_t want)
|
|
{
|
|
struct kvm_lock_waiting *w;
|
|
int cpu;
|
|
u64 start;
|
|
unsigned long flags;
|
|
__ticket_t head;
|
|
|
|
if (in_nmi())
|
|
return;
|
|
|
|
w = this_cpu_ptr(&klock_waiting);
|
|
cpu = smp_processor_id();
|
|
start = spin_time_start();
|
|
|
|
/*
|
|
* Make sure an interrupt handler can't upset things in a
|
|
* partially setup state.
|
|
*/
|
|
local_irq_save(flags);
|
|
|
|
/*
|
|
* The ordering protocol on this is that the "lock" pointer
|
|
* may only be set non-NULL if the "want" ticket is correct.
|
|
* If we're updating "want", we must first clear "lock".
|
|
*/
|
|
w->lock = NULL;
|
|
smp_wmb();
|
|
w->want = want;
|
|
smp_wmb();
|
|
w->lock = lock;
|
|
|
|
add_stats(TAKEN_SLOW, 1);
|
|
|
|
/*
|
|
* This uses set_bit, which is atomic but we should not rely on its
|
|
* reordering gurantees. So barrier is needed after this call.
|
|
*/
|
|
cpumask_set_cpu(cpu, &waiting_cpus);
|
|
|
|
barrier();
|
|
|
|
/*
|
|
* Mark entry to slowpath before doing the pickup test to make
|
|
* sure we don't deadlock with an unlocker.
|
|
*/
|
|
__ticket_enter_slowpath(lock);
|
|
|
|
/* make sure enter_slowpath, which is atomic does not cross the read */
|
|
smp_mb__after_atomic();
|
|
|
|
/*
|
|
* check again make sure it didn't become free while
|
|
* we weren't looking.
|
|
*/
|
|
head = READ_ONCE(lock->tickets.head);
|
|
if (__tickets_equal(head, want)) {
|
|
add_stats(TAKEN_SLOW_PICKUP, 1);
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* halt until it's our turn and kicked. Note that we do safe halt
|
|
* for irq enabled case to avoid hang when lock info is overwritten
|
|
* in irq spinlock slowpath and no spurious interrupt occur to save us.
|
|
*/
|
|
if (arch_irqs_disabled_flags(flags))
|
|
halt();
|
|
else
|
|
safe_halt();
|
|
|
|
out:
|
|
cpumask_clear_cpu(cpu, &waiting_cpus);
|
|
w->lock = NULL;
|
|
local_irq_restore(flags);
|
|
spin_time_accum_blocked(start);
|
|
}
|
|
PV_CALLEE_SAVE_REGS_THUNK(kvm_lock_spinning);
|
|
|
|
/* Kick vcpu waiting on @lock->head to reach value @ticket */
|
|
static void kvm_unlock_kick(struct arch_spinlock *lock, __ticket_t ticket)
|
|
{
|
|
int cpu;
|
|
|
|
add_stats(RELEASED_SLOW, 1);
|
|
for_each_cpu(cpu, &waiting_cpus) {
|
|
const struct kvm_lock_waiting *w = &per_cpu(klock_waiting, cpu);
|
|
if (READ_ONCE(w->lock) == lock &&
|
|
READ_ONCE(w->want) == ticket) {
|
|
add_stats(RELEASED_SLOW_KICKED, 1);
|
|
kvm_kick_cpu(cpu);
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
#endif /* !CONFIG_QUEUED_SPINLOCKS */
|
|
|
|
/*
|
|
* Setup pv_lock_ops to exploit KVM_FEATURE_PV_UNHALT if present.
|
|
*/
|
|
void __init kvm_spinlock_init(void)
|
|
{
|
|
if (!kvm_para_available())
|
|
return;
|
|
/* Does host kernel support KVM_FEATURE_PV_UNHALT? */
|
|
if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
|
|
return;
|
|
|
|
#ifdef CONFIG_QUEUED_SPINLOCKS
|
|
__pv_init_lock_hash();
|
|
pv_lock_ops.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
|
|
pv_lock_ops.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock);
|
|
pv_lock_ops.wait = kvm_wait;
|
|
pv_lock_ops.kick = kvm_kick_cpu;
|
|
#else /* !CONFIG_QUEUED_SPINLOCKS */
|
|
pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(kvm_lock_spinning);
|
|
pv_lock_ops.unlock_kick = kvm_unlock_kick;
|
|
#endif
|
|
}
|
|
|
|
static __init int kvm_spinlock_init_jump(void)
|
|
{
|
|
if (!kvm_para_available())
|
|
return 0;
|
|
if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
|
|
return 0;
|
|
|
|
static_key_slow_inc(¶virt_ticketlocks_enabled);
|
|
printk(KERN_INFO "KVM setup paravirtual spinlock\n");
|
|
|
|
return 0;
|
|
}
|
|
early_initcall(kvm_spinlock_init_jump);
|
|
|
|
#endif /* CONFIG_PARAVIRT_SPINLOCKS */
|