linux-kernel - Re: [PATCH v5 05/14] vfio/mdev: idxd: add basic mdev registration and helper functions

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Date:   Mon, 1 Mar 2021 17:23:47 -0700
From:   Dave Jiang <dave.jiang@...el.com>
To:     Jason Gunthorpe <jgg@...dia.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, parav@...lanox.com, netanelg@...lanox.com,
        shahafs@...lanox.com, pbonzini@...hat.com,
        dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH v5 05/14] vfio/mdev: idxd: add basic mdev registration and
 helper functions


On 2/10/2021 4:59 PM, Jason Gunthorpe wrote:
> On Fri, Feb 05, 2021 at 01:53:24PM -0700, Dave Jiang wrote:

<-- cut for brevity -->


> +static int vdcm_idxd_set_msix_trigger(struct vdcm_idxd *vidxd,
> +				      unsigned int index, unsigned int start,
> +				      unsigned int count, uint32_t flags,
> +				      void *data)
> +{
> +	int i, rc = 0;
> +
> +	if (count > VIDXD_MAX_MSIX_ENTRIES - 1)
> +		count = VIDXD_MAX_MSIX_ENTRIES - 1;
> +
> +	if (count == 0 && (flags & VFIO_IRQ_SET_DATA_NONE)) {
> +		/* Disable all MSIX entries */
> +		for (i = 0; i < VIDXD_MAX_MSIX_ENTRIES; i++) {
> +			rc = msix_trigger_unregister(vidxd, i);
> +			if (rc < 0)
> +				return rc;
> +		}
> +		return 0;
> +	}
> +
> +	for (i = 0; i < count; i++) {
> +		if (flags & VFIO_IRQ_SET_DATA_EVENTFD) {
> +			u32 fd = *(u32 *)(data + i * sizeof(u32));
> +
> +			rc = msix_trigger_register(vidxd, fd, i);
> +			if (rc < 0)
> +				return rc;
> +		} else if (flags & VFIO_IRQ_SET_DATA_NONE) {
> +			rc = msix_trigger_unregister(vidxd, i);
> +			if (rc < 0)
> +				return rc;
> +		}
> +	}
> +	return rc;
> +}
> +
> +static int idxd_vdcm_set_irqs(struct vdcm_idxd *vidxd, uint32_t flags,
> +			      unsigned int index, unsigned int start,
> +			      unsigned int count, void *data)
> +{
> +	int (*func)(struct vdcm_idxd *vidxd, unsigned int index,
> +		    unsigned int start, unsigned int count, uint32_t flags,
> +		    void *data) = NULL;
> +	struct mdev_device *mdev = vidxd->vdev.mdev;
> +	struct device *dev = mdev_dev(mdev);
> +
> +	switch (index) {
> +	case VFIO_PCI_INTX_IRQ_INDEX:
> +		dev_warn(dev, "intx interrupts not supported.\n");
> +		break;
> +	case VFIO_PCI_MSI_IRQ_INDEX:
> +		dev_dbg(dev, "msi interrupt.\n");
> +		switch (flags & VFIO_IRQ_SET_ACTION_TYPE_MASK) {
> +		case VFIO_IRQ_SET_ACTION_MASK:
> +		case VFIO_IRQ_SET_ACTION_UNMASK:
> +			break;
> +		case VFIO_IRQ_SET_ACTION_TRIGGER:
> +			func = vdcm_idxd_set_msix_trigger;
> This would be a good place to insert a common VFIO helper library to
> take care of the MSI-X emulation for IMS.

Hi Jason,

So after looking at the code in vfio_pci_intrs.c, I agree that the 
set_irqs code between VFIO_PCI and this driver can be made in common. 
Given that Alex doesn't want a vfio_pci device embedded in the driver, I 
think we'll need some sort of generic VFIO device that can be used from 
the vfio_pci side and vfio_mdev side to pass down in order to have 
common support library functions. Do you have any thoughts on how to do 
this cleanly architecturally? Also, with vfio_pci common split [1] still 
being worked on, do you think we can defer the work on making the 
interrupt setup code common until the vfio_pci split work settles? Thanks!

[1]: https://lore.kernel.org/kvm/20210201162828.5938-1-mgurtovoy@nvidia.com/