On 10/04/2010 05:56 PM, Gleb Natapov wrote:
When async PF capability is detected hook up special page fault handler
that will handle async page fault events and bypass other page faults to
regular page fault handler. Also add async PF handling to nested SVM
emulation. Async PF always generates exit to L1 where vcpu thread will
be scheduled out until page is available.
Please separate guest and host changes.
+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);
+
+ 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);
+ return;
+ }
+
+ n.token = token;
+ n.cpu = smp_processor_id();
+ 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 (hlist_unhashed(&n.link))
+ break;
+ local_irq_enable();
Suppose we take another apf here. And another, and another (for
different pages, while executing schedule()). What's to prevent kernel
stack overflow?
+ schedule();
+ local_irq_disable();
+ }
+ finish_wait(&n.wq,&wait);
+
+ return;
+}
+EXPORT_SYMBOL_GPL(kvm_async_pf_task_wait);
+
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
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