From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Auger Subject: Re: [PATCH v9 12/18] vfio: Register/unregister irq_bypass_producer Date: Thu, 28 Apr 2016 17:35:12 +0200 Message-ID: <57222DB0.7080205@linaro.org> 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: <20160426140816.67b8b37c-1yVPhWWZRC1BDLzU/O5InQ@public.gmane.org> 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: Alex Williamson , Feng Wu Cc: kvm-u79uwXL29TY76Z2rM5mHXA@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 Hi Alex, On 04/26/2016 10:08 PM, Alex Williamson wrote: > 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, Regarding the ARM IRQ forwarding use case, I think it is OK to fail silently. We would fall back to the irqfd standard mechanism. Anyway this series still is waiting for ARM new-vgic dependency to be resolved, as discussed with Christoffer and Marc. Best Regards Eric > > Alex >