If async page fault is received by idle task or when preemp_count is not zero guest cannot reschedule, so do sti; hlt and wait for page to be ready. vcpu can still process interrupts while it waits for the page to be ready.
Signed-off-by: Gleb Natapov <[email protected]> --- arch/x86/kernel/kvm.c | 31 +++++++++++++++++++++++++++---- 1 files changed, 27 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 09444c9..0836d9a 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -63,6 +63,7 @@ struct kvm_task_sleep_node { struct hlist_node link; wait_queue_head_t wq; u32 token; + int cpu; }; static struct kvm_task_sleep_head { @@ -91,6 +92,11 @@ static void apf_task_wait(struct task_struct *tsk, u32 token) struct kvm_task_sleep_head *b = &async_pf_sleepers[key]; struct kvm_task_sleep_node n, *e; DEFINE_WAIT(wait); + int cpu, idle; + + cpu = get_cpu(); + idle = idle_cpu(cpu); + put_cpu(); spin_lock(&b->lock); e = _find_apf_task(b, token); @@ -105,15 +111,30 @@ static void apf_task_wait(struct task_struct *tsk, u32 token) n.token = token; init_waitqueue_head(&n.wq); hlist_add_head(&n.link, &b->list); + if (idle || preempt_count() > 1) + n.cpu = smp_processor_id(); + else + n.cpu = -1; spin_unlock(&b->lock); for (;;) { - prepare_to_wait(&n.wq, &wait, TASK_UNINTERRUPTIBLE); + if (n.cpu < 0) + prepare_to_wait(&n.wq, &wait, TASK_UNINTERRUPTIBLE); if (hlist_unhashed(&n.link)) break; - schedule(); + + if (n.cpu < 0) { + schedule(); + } else { + /* + * We cannot reschedule. So halt. + */ + native_safe_halt(); + local_irq_disable(); + } } - finish_wait(&n.wq, &wait); + if (n.cpu < 0) + finish_wait(&n.wq, &wait); return; } @@ -146,7 +167,9 @@ again: hlist_add_head(&n->link, &b->list); } else { hlist_del_init(&n->link); - if (waitqueue_active(&n->wq)) + if (n->cpu >= 0) + smp_send_reschedule(n->cpu); + else if (waitqueue_active(&n->wq)) wake_up(&n->wq); } spin_unlock(&b->lock); -- 1.6.5 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
