Messages in this thread | | | Date | Thu, 07 Oct 2010 15:10:27 +0200 | From | Avi Kivity <> | Subject | Re: [PATCH v6 08/12] Handle async PF in a guest. |
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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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