diff options
author | Gleb Natapov <gleb@redhat.com> | 2010-10-14 11:22:54 +0200 |
---|---|---|
committer | Avi Kivity <avi@redhat.com> | 2011-01-12 11:23:19 +0200 |
commit | 6c047cd982f944fa63b2d96de2a06463d113f9fa (patch) | |
tree | 33ea24341320d9adda2d2d3c0314a7244bac7862 | |
parent | 7c90705bf2a373aa238661bdb6446f27299ef489 (diff) | |
download | op-kernel-dev-6c047cd982f944fa63b2d96de2a06463d113f9fa.zip op-kernel-dev-6c047cd982f944fa63b2d96de2a06463d113f9fa.tar.gz |
KVM paravirt: Handle async PF in non preemptable context
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.
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
-rw-r--r-- | arch/x86/kernel/kvm.c | 40 |
1 files changed, 34 insertions, 6 deletions
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index d564063..47ea93e 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -37,6 +37,7 @@ #include <asm/cpu.h> #include <asm/traps.h> #include <asm/desc.h> +#include <asm/tlbflush.h> #define MMU_QUEUE_SIZE 1024 @@ -78,6 +79,8 @@ struct kvm_task_sleep_node { wait_queue_head_t wq; u32 token; int cpu; + bool halted; + struct mm_struct *mm; }; static struct kvm_task_sleep_head { @@ -106,6 +109,11 @@ void kvm_async_pf_task_wait(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); @@ -119,19 +127,33 @@ void kvm_async_pf_task_wait(u32 token) n.token = token; n.cpu = smp_processor_id(); + n.mm = current->active_mm; + n.halted = idle || preempt_count() > 1; + atomic_inc(&n.mm->mm_count); init_waitqueue_head(&n.wq); hlist_add_head(&n.link, &b->list); spin_unlock(&b->lock); for (;;) { - prepare_to_wait(&n.wq, &wait, TASK_UNINTERRUPTIBLE); + if (!n.halted) + prepare_to_wait(&n.wq, &wait, TASK_UNINTERRUPTIBLE); if (hlist_unhashed(&n.link)) break; - local_irq_enable(); - schedule(); - local_irq_disable(); + + if (!n.halted) { + local_irq_enable(); + schedule(); + local_irq_disable(); + } else { + /* + * We cannot reschedule. So halt. + */ + native_safe_halt(); + local_irq_disable(); + } } - finish_wait(&n.wq, &wait); + if (!n.halted) + finish_wait(&n.wq, &wait); return; } @@ -140,7 +162,12 @@ EXPORT_SYMBOL_GPL(kvm_async_pf_task_wait); static void apf_task_wake_one(struct kvm_task_sleep_node *n) { hlist_del_init(&n->link); - if (waitqueue_active(&n->wq)) + if (!n->mm) + return; + mmdrop(n->mm); + if (n->halted) + smp_send_reschedule(n->cpu); + else if (waitqueue_active(&n->wq)) wake_up(&n->wq); } @@ -193,6 +220,7 @@ again: } n->token = token; n->cpu = smp_processor_id(); + n->mm = NULL; init_waitqueue_head(&n->wq); hlist_add_head(&n->link, &b->list); } else |