linux-kernel - Re: [PATCH] vfio/cdx: add support for CDX bus

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Date:   Wed, 5 Apr 2023 12:33:39 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Nipun Gupta <nipun.gupta@....com>
Cc:     alex.williamson@...hat.com, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, git@....com, harpreet.anand@....com,
        michal.simek@....com
Subject: Re: [PATCH] vfio/cdx: add support for CDX bus

On Mon, Apr 03, 2023 at 07:55:25PM +0530, Nipun Gupta wrote:

> +enum {
> +	CDX_ID_F_VFIO_DRIVER_OVERRIDE = 1,
> +};

This seems to be missing the file2alias part.

> +static void vfio_cdx_regions_cleanup(struct vfio_cdx_device *vdev)
> +{
> +	kfree(vdev->regions);
> +}
> +
> +static int vfio_cdx_reset_device(struct vfio_cdx_device *vdev)
> +{
> +	return cdx_dev_reset(&vdev->cdx_dev->dev);
> +}

Wrapper functions should be avoided.

> +static void vfio_cdx_close_device(struct vfio_device *core_vdev)
> +{
> +	struct vfio_cdx_device *vdev =
> +		container_of(core_vdev, struct vfio_cdx_device, vdev);
> +	int ret;
> +
> +	vfio_cdx_regions_cleanup(vdev);
> +
> +	/* reset the device before cleaning up the interrupts */
> +	ret = vfio_cdx_reset_device(vdev);
> +	if (WARN_ON(ret))
> +		dev_warn(core_vdev->dev,
> +			 "VFIO_CDX: reset device has failed (%d)\n", ret);

This is pretty problematic.. if the reset can fail the device is
returned to the system in an unknown state and it seems pretty likely
that it can be a way to attack the kernel.

> +	case VFIO_DEVICE_RESET:
> +	{
> +		return vfio_cdx_reset_device(vdev);
> +	}

What happens to MMIO access during this reset?

> +static int vfio_cdx_mmap_mmio(struct vfio_cdx_region region,
> +			      struct vm_area_struct *vma)
> +{
> +	u64 size = vma->vm_end - vma->vm_start;
> +	u64 pgoff, base;
> +
> +	pgoff = vma->vm_pgoff &
> +		((1U << (VFIO_CDX_OFFSET_SHIFT - PAGE_SHIFT)) - 1);
> +	base = pgoff << PAGE_SHIFT;
> +
> +	if (region.size < PAGE_SIZE || base + size > region.size)
> +		return -EINVAL;
> +
> +	vma->vm_pgoff = (region.addr >> PAGE_SHIFT) + pgoff;
> +	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);

pgprot_device

> +	return remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
> +			       size, vma->vm_page_prot);

io_remap_pfn_range
> +static int vfio_cdx_mmap(struct vfio_device *core_vdev,
> +			 struct vm_area_struct *vma)
> +{
> +	struct vfio_cdx_device *vdev =
> +		container_of(core_vdev, struct vfio_cdx_device, vdev);
> +	struct cdx_device *cdx_dev = vdev->cdx_dev;
> +	unsigned int index;
> +
> +	index = vma->vm_pgoff >> (VFIO_CDX_OFFSET_SHIFT - PAGE_SHIFT);
> +
> +	if (vma->vm_end < vma->vm_start)
> +		return -EINVAL;
> +	if (vma->vm_start & ~PAGE_MASK)
> +		return -EINVAL;
> +	if (vma->vm_end & ~PAGE_MASK)
> +		return -EINVAL;

The core code already assures these checks.

> +	if (!(vma->vm_flags & VM_SHARED))
> +		return -EINVAL;
> +	if (index >= cdx_dev->res_count)
> +		return -EINVAL;
> +
> +	if (!(vdev->regions[index].flags & VFIO_REGION_INFO_FLAG_MMAP))
> +		return -EINVAL;
> +
> +	if (!(vdev->regions[index].flags & VFIO_REGION_INFO_FLAG_READ) &&
> +	    (vma->vm_flags & VM_READ))
> +		return -EINVAL;
> +
> +	if (!(vdev->regions[index].flags & VFIO_REGION_INFO_FLAG_WRITE) &&
> +	    (vma->vm_flags & VM_WRITE))
> +		return -EINVAL;
> +
> +	vma->vm_private_data = cdx_dev;

not needed

> diff --git a/drivers/vfio/cdx/vfio_cdx_private.h b/drivers/vfio/cdx/vfio_cdx_private.h
> new file mode 100644
> index 000000000000..8b6f1ee3f5cd
> --- /dev/null
> +++ b/drivers/vfio/cdx/vfio_cdx_private.h
> @@ -0,0 +1,32 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2022-2023, Advanced Micro Devices, Inc.
> + */
> +
> +#ifndef VFIO_CDX_PRIVATE_H
> +#define VFIO_CDX_PRIVATE_H
> +
> +#define VFIO_CDX_OFFSET_SHIFT    40
> +#define VFIO_CDX_OFFSET_MASK (((u64)(1) << VFIO_CDX_OFFSET_SHIFT) - 1)
> +
> +#define VFIO_CDX_OFFSET_TO_INDEX(off) ((off) >> VFIO_CDX_OFFSET_SHIFT)
> +
> +#define VFIO_CDX_INDEX_TO_OFFSET(index)	\
> +	((u64)(index) << VFIO_CDX_OFFSET_SHIFT)

use static inlines for function-line macros

> +struct vfio_cdx_region {
> +	u32			flags;
> +	u32			type;
> +	u64			addr;
> +	resource_size_t		size;
> +	void __iomem		*ioaddr;
> +};
> +
> +struct vfio_cdx_device {
> +	struct vfio_device	vdev;
> +	struct cdx_device	*cdx_dev;
> +	struct device		*dev;
> +	struct vfio_cdx_region	*regions;
> +};

This header file does not seem necessary right now

Jason