From 9db284f30311b741a5e74eb8e5800ff7b92c4be3 Mon Sep 17 00:00:00 2001 From: Rik van Riel Date: Mon, 21 Mar 2016 15:13:27 +0100 Subject: [PATCH] kvm, rt: change async pagefault code locking for PREEMPT_RT The async pagefault wake code can run from the idle task in exception context, so everything here needs to be made non-preemptible. Conversion to a simple wait queue and raw spinlock does the trick. Signed-off-by: Rik van Riel Signed-off-by: Paolo Bonzini --- arch/x86/kernel/kvm.c | 37 +++++++++++++++++++------------------ 1 file changed, 19 insertions(+), 18 deletions(-) diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 47190bd399e7..807950860fb7 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -36,6 +36,7 @@ #include #include #include +#include #include #include #include @@ -91,14 +92,14 @@ static void kvm_io_delay(void) struct kvm_task_sleep_node { struct hlist_node link; - wait_queue_head_t wq; + struct swait_queue_head wq; u32 token; int cpu; bool halted; }; static struct kvm_task_sleep_head { - spinlock_t lock; + raw_spinlock_t lock; struct hlist_head list; } async_pf_sleepers[KVM_TASK_SLEEP_HASHSIZE]; @@ -122,17 +123,17 @@ void kvm_async_pf_task_wait(u32 token) u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS); struct kvm_task_sleep_head *b = &async_pf_sleepers[key]; struct kvm_task_sleep_node n, *e; - DEFINE_WAIT(wait); + DECLARE_SWAITQUEUE(wait); rcu_irq_enter(); - spin_lock(&b->lock); + raw_spin_lock(&b->lock); e = _find_apf_task(b, token); if (e) { /* dummy entry exist -> wake up was delivered ahead of PF */ hlist_del(&e->link); kfree(e); - spin_unlock(&b->lock); + raw_spin_unlock(&b->lock); rcu_irq_exit(); return; @@ -141,13 +142,13 @@ void kvm_async_pf_task_wait(u32 token) n.token = token; n.cpu = smp_processor_id(); n.halted = is_idle_task(current) || preempt_count() > 1; - init_waitqueue_head(&n.wq); + init_swait_queue_head(&n.wq); hlist_add_head(&n.link, &b->list); - spin_unlock(&b->lock); + raw_spin_unlock(&b->lock); for (;;) { if (!n.halted) - prepare_to_wait(&n.wq, &wait, TASK_UNINTERRUPTIBLE); + prepare_to_swait(&n.wq, &wait, TASK_UNINTERRUPTIBLE); if (hlist_unhashed(&n.link)) break; @@ -166,7 +167,7 @@ void kvm_async_pf_task_wait(u32 token) } } if (!n.halted) - finish_wait(&n.wq, &wait); + finish_swait(&n.wq, &wait); rcu_irq_exit(); return; @@ -178,8 +179,8 @@ static void apf_task_wake_one(struct kvm_task_sleep_node *n) hlist_del_init(&n->link); if (n->halted) smp_send_reschedule(n->cpu); - else if (waitqueue_active(&n->wq)) - wake_up(&n->wq); + else if (swait_active(&n->wq)) + swake_up(&n->wq); } static void apf_task_wake_all(void) @@ -189,14 +190,14 @@ static void apf_task_wake_all(void) for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++) { struct hlist_node *p, *next; struct kvm_task_sleep_head *b = &async_pf_sleepers[i]; - spin_lock(&b->lock); + raw_spin_lock(&b->lock); hlist_for_each_safe(p, next, &b->list) { struct kvm_task_sleep_node *n = hlist_entry(p, typeof(*n), link); if (n->cpu == smp_processor_id()) apf_task_wake_one(n); } - spin_unlock(&b->lock); + raw_spin_unlock(&b->lock); } } @@ -212,7 +213,7 @@ void kvm_async_pf_task_wake(u32 token) } again: - spin_lock(&b->lock); + raw_spin_lock(&b->lock); n = _find_apf_task(b, token); if (!n) { /* @@ -225,17 +226,17 @@ again: * Allocation failed! Busy wait while other cpu * handles async PF. */ - spin_unlock(&b->lock); + raw_spin_unlock(&b->lock); cpu_relax(); goto again; } n->token = token; n->cpu = smp_processor_id(); - init_waitqueue_head(&n->wq); + init_swait_queue_head(&n->wq); hlist_add_head(&n->link, &b->list); } else apf_task_wake_one(n); - spin_unlock(&b->lock); + raw_spin_unlock(&b->lock); return; } EXPORT_SYMBOL_GPL(kvm_async_pf_task_wake); @@ -486,7 +487,7 @@ void __init kvm_guest_init(void) paravirt_ops_setup(); register_reboot_notifier(&kvm_pv_reboot_nb); for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++) - spin_lock_init(&async_pf_sleepers[i].lock); + raw_spin_lock_init(&async_pf_sleepers[i].lock); if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF)) x86_init.irqs.trap_init = kvm_apf_trap_init; -- 2.20.1