From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Williamson Subject: Re: [PATCH v9 12/18] vfio: Register/unregister irq_bypass_producer Date: Thu, 28 Apr 2016 10:40:28 -0600 Message-ID: <20160428104028.63ff2109@t450s.home> References: <1442586596-5920-1-git-send-email-feng.wu@intel.com> <1442586596-5920-13-git-send-email-feng.wu@intel.com> <20160426140816.67b8b37c@t450s.home> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: "Wu, Feng" Cc: "kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "eric.auger-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org" , "mtosatti-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" , "pbonzini-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org" List-Id: iommu@lists.linux-foundation.org On Wed, 27 Apr 2016 01:32:32 +0000 "Wu, Feng" wrote: > > -----Original Message----- > > From: Alex Williamson [mailto:alex.williamson-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org] > > Sent: Wednesday, April 27, 2016 4:08 AM > > To: Wu, Feng > > Cc: pbonzini-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org; joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org; mtosatti-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org; > > eric.auger-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org; kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; iommu-cunTk1MwBs/ROKNJybVBZg@public.gmane.org > > foundation.org; linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > > Subject: Re: [PATCH v9 12/18] vfio: Register/unregister irq_bypass_producer > > > > On Fri, 18 Sep 2015 22:29:50 +0800 > > Feng Wu 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