linux-kernel - Re: [PATCH v6 05/20] vfio: mdev: common lib code for setting up Interrupt Message Store

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Date:   Sun, 23 May 2021 21:02:57 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Dave Jiang <dave.jiang@...el.com>
Cc:     alex.williamson@...hat.com, kwankhede@...dia.com,
        tglx@...utronix.de, vkoul@...nel.org, megha.dey@...el.com,
        jacob.jun.pan@...el.com, ashok.raj@...el.com, yi.l.liu@...el.com,
        baolu.lu@...el.com, kevin.tian@...el.com, sanjay.k.kumar@...el.com,
        tony.luck@...el.com, dan.j.williams@...el.com,
        eric.auger@...hat.com, pbonzini@...hat.com,
        dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH v6 05/20] vfio: mdev: common lib code for setting up
 Interrupt Message Store

On Fri, May 21, 2021 at 05:19:36PM -0700, Dave Jiang wrote:
> Add common helper code to setup IMS once the MSI domain has been
> setup by the device driver. The main helper function is
> mdev_ims_set_msix_trigger() that is called by the VFIO ioctl
> VFIO_DEVICE_SET_IRQS. The function deals with the setup and
> teardown of emulated and IMS backed eventfd that gets exported
> to the guest kernel via VFIO as MSIX vectors.
> 
> Suggested-by: Jason Gunthorpe <jgg@...dia.com>
> Signed-off-by: Dave Jiang <dave.jiang@...el.com>
> ---
>  drivers/vfio/mdev/Kconfig     |   12 ++
>  drivers/vfio/mdev/Makefile    |    3 
>  drivers/vfio/mdev/mdev_irqs.c |  318 +++++++++++++++++++++++++++++++++++++++++
>  include/linux/mdev.h          |   51 +++++++
>  4 files changed, 384 insertions(+)
>  create mode 100644 drivers/vfio/mdev/mdev_irqs.c

IMS is not mdev specific, do not entangle it with mdev code. This
should be generic VFIO stuff.

> +static int mdev_msix_set_vector_signal(struct mdev_irq *mdev_irq, int vector, int fd)
> +{
> +	int rc, irq;
> +	struct mdev_device *mdev = irq_to_mdev(mdev_irq);
> +	struct mdev_irq_entry *entry;
> +	struct device *dev = &mdev->dev;
> +	struct eventfd_ctx *trigger;
> +	char *name;
> +	bool pasid_en;
> +	u32 auxval;
> +
> +	if (vector < 0 || vector >= mdev_irq->num)
> +		return -EINVAL;
> +
> +	entry = &mdev_irq->irq_entries[vector];
> +
> +	if (entry->ims)
> +		irq = dev_msi_irq_vector(dev, entry->ims_id);
> +	else
> +		irq = 0;
> +
> +	pasid_en = mdev_irq->pasid != INVALID_IOASID ? true : false;
> +
> +	/* IMS and invalid pasid is not a valid configuration */
> +	if (entry->ims && !pasid_en)
> +		return -EINVAL;
> +
> +	if (entry->trigger) {
> +		if (irq) {
> +			irq_bypass_unregister_producer(&entry->producer);
> +			free_irq(irq, entry->trigger);
> +			if (pasid_en) {
> +				auxval = ims_ctrl_pasid_aux(0, false);
> +				irq_set_auxdata(irq, IMS_AUXDATA_CONTROL_WORD, auxval);
> +			}
> +		}
> +		kfree(entry->name);
> +		eventfd_ctx_put(entry->trigger);
> +		entry->trigger = NULL;
> +	}
> +
> +	if (fd < 0)
> +		return 0;
> +
> +	name = kasprintf(GFP_KERNEL, "vfio-mdev-irq[%d](%s)", vector, dev_name(dev));
> +	if (!name)
> +		return -ENOMEM;
> +
> +	trigger = eventfd_ctx_fdget(fd);
> +	if (IS_ERR(trigger)) {
> +		kfree(name);
> +		return PTR_ERR(trigger);
> +	}
> +
> +	entry->name = name;
> +	entry->trigger = trigger;
> +
> +	if (!irq)
> +		return 0;
> +
> +	if (pasid_en) {
> +		auxval = ims_ctrl_pasid_aux(mdev_irq->pasid, true);
> +		rc = irq_set_auxdata(irq, IMS_AUXDATA_CONTROL_WORD, auxval);
> +		if (rc < 0)
> +			goto err;

Why is anything to do with PASID here? Something has gone wrong with
the layers I suspect..

Oh yes. drivers/irqchip/irq-ims-msi.c is dxd specific and shouldn't be
pretending to be common code.

The protocol to stuff the pasid and other stuff into the auxdata is
also compeltely idxd specific and is just a hacky way to communicate
from this code to the IDXD irq-chip.

So this doesn't belong here either. Pass in the auxdata from the idxd
code and I'd rename the irq-ims-msi to irq-ims-idxd

> +static int mdev_msix_enable(struct mdev_irq *mdev_irq, int nvec)
> +{
> +	struct mdev_device *mdev = irq_to_mdev(mdev_irq);
> +	struct device *dev;
> +	int rc;
> +
> +	if (nvec != mdev_irq->num)
> +		return -EINVAL;
> +
> +	if (mdev_irq->ims_num) {
> +		dev = &mdev->dev;
> +		rc = msi_domain_alloc_irqs(dev_get_msi_domain(dev), dev, mdev_irq->ims_num);

Huh? The PCI device should be the only device touching IRQ stuff. I'm
nervous to see you mix in the mdev struct device into this function.

Isn't the msi_domain just idxd->ims_domain?

Jason