linux-kernel - Re: [PATCH v6 13/20] vfio/mdev: idxd: add mdev driver registration and helper functions

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Message-ID: <20210523233223.GI1002214@nvidia.com>
Date:   Sun, 23 May 2021 20:32:23 -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 13/20] vfio/mdev: idxd: add mdev driver registration
 and helper functions

On Fri, May 21, 2021 at 05:20:26PM -0700, Dave Jiang wrote:
> +static int idxd_vdcm_mmap(struct vfio_device *vdev, struct vm_area_struct *vma)
> +{
> +	unsigned int wq_idx;
> +	unsigned long req_size, pgoff = 0, offset;
> +	pgprot_t pg_prot;
> +	struct vdcm_idxd *vidxd = vdev_to_vidxd(vdev);
> +	struct idxd_wq *wq = vidxd->wq;
> +	struct idxd_device *idxd = vidxd->idxd;
> +	enum idxd_portal_prot virt_portal, phys_portal;
> +	phys_addr_t base = pci_resource_start(idxd->pdev, IDXD_WQ_BAR);
> +	struct device *dev = vdev->dev;
> +
> +	if (!(vma->vm_flags & VM_SHARED))
> +		return -EINVAL;
> +
> +	pg_prot = vma->vm_page_prot;
> +	req_size = vma->vm_end - vma->vm_start;
> +	if (req_size > PAGE_SIZE)
> +		return -EINVAL;
> +
> +	vma->vm_flags |= VM_DONTCOPY;
> +
> +	offset = (vma->vm_pgoff << PAGE_SHIFT) &
> +		 ((1ULL << VFIO_PCI_OFFSET_SHIFT) - 1);
> +
> +	wq_idx = offset >> (PAGE_SHIFT + 2);
> +	if (wq_idx >= 1) {
> +		dev_err(dev, "mapping invalid wq %d off %lx\n",
> +			wq_idx, offset);
> +		return -EINVAL;
> +	}

This is a really wonky and leaky way to say that the vm_pgoff can only
be one of two values? It is uAPI, be thorough.

> +static long idxd_vdcm_ioctl(struct vfio_device *vdev, unsigned int cmd, unsigned long arg)
> +{
> +	struct vdcm_idxd *vidxd = vdev_to_vidxd(vdev);
> +	unsigned long minsz;
> +	int rc = -EINVAL;
> +	struct device *dev = vdev->dev;
> +
> +	dev_dbg(dev, "vidxd %p ioctl, cmd: %d\n", vidxd, cmd);
> +
> +	mutex_lock(&vidxd->dev_lock);
> +	if (cmd == VFIO_DEVICE_GET_INFO) {

Sigh.. This ioctl stuff really needs splitting into proper functions
called by the core code instead of cut&pasting all of this

>  static int idxd_mdev_drv_probe(struct device *dev)
> diff --git a/drivers/vfio/mdev/idxd/mdev.h b/drivers/vfio/mdev/idxd/mdev.h
> index f696fe38e374..dd4290bce772 100644
> +++ b/drivers/vfio/mdev/idxd/mdev.h
> @@ -30,11 +30,26 @@
>  #define VIDXD_MAX_MSIX_ENTRIES		VIDXD_MAX_MSIX_VECS
>  #define VIDXD_MAX_WQS			1
>  
> +#define IDXD_MDEV_NAME_LEN		64

This is never used. Check everything..

Jason