linux-kernel - Re: [PATCH 1/4] vfio: selftests: add iova range query helpers

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Message-ID: <aRJhSkj6S48G_pHI@google.com>
Date: Mon, 10 Nov 2025 22:03:54 +0000
From: David Matlack <dmatlack@...gle.com>
To: Alex Mastro <amastro@...com>
Cc: Alex Williamson <alex@...zbot.org>, Shuah Khan <shuah@...nel.org>,
	kvm@...r.kernel.org, linux-kselftest@...r.kernel.org,
	linux-kernel@...r.kernel.org, Jason Gunthorpe <jgg@...pe.ca>
Subject: Re: [PATCH 1/4] vfio: selftests: add iova range query helpers

On 2025-11-10 01:10 PM, Alex Mastro wrote:
> +/*
> + * Return iova ranges for the device's container. Normalize vfio_iommu_type1 to
> + * report iommufd's iommu_iova_range. Free with free().
> + */
> +static struct iommu_iova_range *vfio_iommu_iova_ranges(struct vfio_pci_device *device,
> +						       size_t *nranges)
> +{
> +	struct vfio_iommu_type1_info_cap_iova_range *cap_range;
> +	struct vfio_iommu_type1_info *buf;

nit: Maybe name this variable `info` here and in vfio_iommu_info_buf()
and vfio_iommu_info_cap_hdr()? It is not an opaque buffer.

> +	struct vfio_info_cap_header *hdr;
> +	struct iommu_iova_range *ranges = NULL;
> +
> +	buf = vfio_iommu_info_buf(device);

nit: How about naming this vfio_iommu_get_info() since it actually
fetches the info from VFIO? (It doesn't just allocate a buffer.)

> +	VFIO_ASSERT_NOT_NULL(buf);

This assert is unnecessary.

> +
> +	hdr = vfio_iommu_info_cap_hdr(buf, VFIO_IOMMU_TYPE1_INFO_CAP_IOVA_RANGE);
> +	if (!hdr)
> +		goto free_buf;

Is this to account for running on old versions of VFIO? Or are there
some scenarios when VFIO can't report the list of IOVA ranges?

> +
> +	cap_range = container_of(hdr, struct vfio_iommu_type1_info_cap_iova_range, header);
> +	if (!cap_range->nr_iovas)
> +		goto free_buf;
> +
> +	ranges = malloc(cap_range->nr_iovas * sizeof(*ranges));
> +	VFIO_ASSERT_NOT_NULL(ranges);
> +
> +	for (u32 i = 0; i < cap_range->nr_iovas; i++) {
> +		ranges[i] = (struct iommu_iova_range){
> +			.start = cap_range->iova_ranges[i].start,
> +			.last = cap_range->iova_ranges[i].end,
> +		};
> +	}
> +
> +	*nranges = cap_range->nr_iovas;
> +
> +free_buf:
> +	free(buf);
> +	return ranges;
> +}
> +
> +/* Return iova ranges of the device's IOAS. Free with free() */
> +struct iommu_iova_range *iommufd_iova_ranges(struct vfio_pci_device *device,
> +					     size_t *nranges)
> +{
> +	struct iommu_iova_range *ranges;
> +	int ret;
> +
> +	struct iommu_ioas_iova_ranges query = {
> +		.size = sizeof(query),
> +		.ioas_id = device->ioas_id,
> +	};
> +
> +	ret = ioctl(device->iommufd, IOMMU_IOAS_IOVA_RANGES, &query);
> +	VFIO_ASSERT_EQ(ret, -1);
> +	VFIO_ASSERT_EQ(errno, EMSGSIZE);
> +	VFIO_ASSERT_GT(query.num_iovas, 0);
> +
> +	ranges = malloc(query.num_iovas * sizeof(*ranges));
> +	VFIO_ASSERT_NOT_NULL(ranges);
> +
> +	query.allowed_iovas = (uintptr_t)ranges;
> +
> +	ioctl_assert(device->iommufd, IOMMU_IOAS_IOVA_RANGES, &query);
> +	*nranges = query.num_iovas;
> +
> +	return ranges;
> +}
> +
> +struct iommu_iova_range *vfio_pci_iova_ranges(struct vfio_pci_device *device,
> +					      size_t *nranges)

nit: Both iommufd and VFIO represent the number of IOVA ranges as a u32.
Perhaps we should do the same in VFIO selftests?