On 06/05/2011 08:54 PM, Alexander Graf wrote: > On 05.06.2011, at 19:48, Jan Kiszka wrote: > > > On 2011-06-05 19:19, Alexander Graf wrote: > >> > >> On 05.06.2011, at 18:33, Avi Kivity wrote: > >> > >>> On 06/05/2011 07:30 PM, Alexander Graf wrote: > >>>>>> > >>>>>> Could you elaborate what you mean here? I'm not really following. Are > >>>>>> you suggesting a new arch-generic interface? (Pardon my ignorance). > >>>>> > >>>>> Using KVM_IRQ_LINE everywhere except s390, not just in x86 and ARM. > >>>> > >>>> An in-kernel MPIC implementation is coming for PPC, so I don't see any reason to switch from something that works now. > >>> > >>> Right, this is spilled milk. > >>> > >>> Does the ppc qemu implementation raise KVM_INTERRUPT solely from the vcpu thread? > >> > >> Well, without iothread it used to obviously. Now that we have an iothread, it calls ioctl(KVM_INTERRUPT) from a separate thread. The code also doesn't forcefully wake up the vcpu thread, so yes, I think here's a chance for at least delaying interrupt delivery. Chances are pretty slim we don't get out of the vcpu thread at all :). > > > > There are good chances to run into a deadlock when calling a per-vcpu > > IOCTL over a foreign context: calling thread holds qemu_mutex and blocks > > on kvm_mutex inside the kernel, target vcpu is running endless guest > > loop, holding kvm_mutex, all other qemu threads will sooner or later > > block on the global lock. That's at least one pattern you can get on x86 > > (we had a few of such bugs in the past). > > Any recommendations? Should we just signal the main thread when we want to inject an interrupt? > Signal the vcpu thread, of course. There's on_vcpu (or on_cpu, don't know how it's called today) for that. -- error compiling committee.c: too many arguments to function
