On Thu, Oct 07, 2010 at 03:10:27PM +0200, Avi Kivity wrote: > 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? > Host side keeps track of outstanding apfs and will not send apf for the same phys address twice. It will halt vcpu instead. > >+ 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. -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html