On Wed, 27 Apr 2016 01:32:32 +0000 "Wu, Feng" <feng.wu@xxxxxxxxx> wrote: > > -----Original Message----- > > From: Alex Williamson [mailto:alex.williamson@xxxxxxxxxx] > > Sent: Wednesday, April 27, 2016 4:08 AM > > To: Wu, Feng <feng.wu@xxxxxxxxx> > > Cc: pbonzini@xxxxxxxxxx; joro@xxxxxxxxxx; mtosatti@xxxxxxxxxx; > > eric.auger@xxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; iommu@lists.linux- > > foundation.org; linux-kernel@xxxxxxxxxxxxxxx > > Subject: Re: [PATCH v9 12/18] vfio: Register/unregister irq_bypass_producer > > > > On Fri, 18 Sep 2015 22:29:50 +0800 > > Feng Wu <feng.wu@xxxxxxxxx> wrote: > > > > @@ -360,6 +361,14 @@ static int vfio_msi_set_vector_signal(struct > > vfio_pci_device *vdev, > > > return ret; > > > } > > > > > > + vdev->ctx[vector].producer.token = trigger; > > > + vdev->ctx[vector].producer.irq = irq; > > > + ret = irq_bypass_register_producer(&vdev->ctx[vector].producer); > > > + if (unlikely(ret)) > > > + dev_info(&pdev->dev, > > > + "irq bypass producer (token %p) registeration fails: %d\n", > > > + vdev->ctx[vector].producer.token, ret); > > > + > > > vdev->ctx[vector].trigger = trigger; > > > > > > return 0; > > > > Digging back into the IRQ producer/consumer thing, I'm not sure how we > > should be handling a failure here, but it turns out that what we have > > is pretty sub-optimal. Any sort of testing on AMD hits this dev_info > > because kvm_arch_irq_bypass_add_producer() returns -EINVAL without > > kvm_x86_ops->update_pi_irte which is only implemented for vmx. Clearly > > we don't want to spew confusing error messages for a feature that does > > not exist. > > > > The easiest option is to simply make this error silent, but should > > registering a producer/consumer really fail due to a mismatch on the > > other end or should the __connect sequence fail silently, which both > > ends would know about (if they care) due to the add/del handshake > > between them? Perhaps for now we simply need a stable suitable fix to > > silence the dev_info above, but longer term, registration shouldn't > > fail for mismatches like this. Thoughts? Thanks, > > Can we just return 0 when kvm_x86_ops->update_pi_irte is NULL in > kvm_arch_irq_bypass_add_producer? Yeah, that may be the best way to go, only return error for actual failures, not for simple lack of a bypass mechanism. This is consistent with what update_pi_irte does when running on hardware or configurations without PI. Thanks, Alex -- 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
