Messages in this thread | | | Date | Thu, 07 Oct 2010 19:18:03 +0200 | From | Avi Kivity <> | Subject | Re: [PATCH v6 08/12] Handle async PF in a guest. |
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On 10/07/2010 07:14 PM, Gleb Natapov wrote: > 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.
What about different pages, running the scheduler code?
Oh, and we'll run the scheduler recursively.
-- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.
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