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SubjectRe: [PATCH v9 12/18] vfio: Register/unregister irq_bypass_producer
On Fri, 18 Sep 2015 22:29:50 +0800
Feng Wu <feng.wu@intel.com> 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,

Alex

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