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Date:   Fri, 16 Feb 2018 15:12:23 -0700
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>
Cc:     <eric.auger@...hat.com>, <pmorel@...ux.vnet.ibm.com>,
        <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linuxarm@...wei.com>, <john.garry@...wei.com>,
        <xuwei5@...ilicon.com>
Subject: Re: [PATCH v3 5/6] vfio/type1: Add IOVA range capability support

On Thu, 15 Feb 2018 09:45:03 +0000
Shameer Kolothum <shameerali.kolothum.thodi@...wei.com> wrote:

> This  allows the user-space to retrieve the supported IOVA
> range(s), excluding any reserved regions. The implementation
> is based on capability chains, added to VFIO_IOMMU_GET_INFO ioctl.
> 
> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 92 +++++++++++++++++++++++++++++++++++++++++
>  include/uapi/linux/vfio.h       | 23 +++++++++++
>  2 files changed, 115 insertions(+)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index dae01c5..21e575c 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -1925,6 +1925,68 @@ static int vfio_domains_have_iommu_cache(struct vfio_iommu *iommu)
>  	return ret;
>  }
>  
> +static int vfio_add_iova_cap(struct vfio_info_cap *caps,
> +		 struct vfio_iommu_type1_info_cap_iova_range *cap_iovas,
> +		 size_t size)
> +{
> +	struct vfio_info_cap_header *header;
> +	struct vfio_iommu_type1_info_cap_iova_range *iova_cap;
> +
> +	header = vfio_info_cap_add(caps, size,
> +				VFIO_IOMMU_TYPE1_INFO_CAP_IOVA_RANGE, 1);
> +	if (IS_ERR(header))
> +		return PTR_ERR(header);
> +
> +	iova_cap = container_of(header,
> +			struct vfio_iommu_type1_info_cap_iova_range, header);
> +	iova_cap->nr_iovas = cap_iovas->nr_iovas;
> +	memcpy(iova_cap->iova_ranges, cap_iovas->iova_ranges,
> +		cap_iovas->nr_iovas * sizeof(*cap_iovas->iova_ranges));
> +	return 0;
> +}
> +
> +static int vfio_build_iommu_iova_caps(struct vfio_iommu *iommu,
> +				struct vfio_info_cap *caps)
> +{
> +	struct vfio_iommu_type1_info_cap_iova_range *cap_iovas;
> +	struct vfio_iova *iova;
> +	size_t size;
> +	int iovas = 0, i = 0, ret;
> +
> +	mutex_lock(&iommu->lock);
> +
> +	list_for_each_entry(iova, &iommu->iova_list, list)
> +		iovas++;
> +
> +	if (!iovas) {
> +		ret = -EINVAL;
> +		goto out_unlock;
> +	}
> +
> +	size = sizeof(*cap_iovas) + (iovas * sizeof(*cap_iovas->iova_ranges));
> +
> +	cap_iovas = kzalloc(size, GFP_KERNEL);
> +	if (!cap_iovas) {
> +		ret = -ENOMEM;
> +		goto out_unlock;
> +	}
> +
> +	cap_iovas->nr_iovas = iovas;
> +
> +	list_for_each_entry(iova, &iommu->iova_list, list) {
> +		cap_iovas->iova_ranges[i].start = iova->start;
> +		cap_iovas->iova_ranges[i].end = iova->end;
> +		i++;
> +	}
> +
> +	ret = vfio_add_iova_cap(caps, cap_iovas, size);
> +
> +	kfree(cap_iovas);
> +out_unlock:
> +	mutex_unlock(&iommu->lock);
> +	return ret;
> +}
> +
>  static long vfio_iommu_type1_ioctl(void *iommu_data,
>  				   unsigned int cmd, unsigned long arg)
>  {
> @@ -1946,6 +2008,8 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
>  		}
>  	} else if (cmd == VFIO_IOMMU_GET_INFO) {
>  		struct vfio_iommu_type1_info info;
> +		struct vfio_info_cap caps = { .buf = NULL, .size = 0 };
> +		int ret;
>  
>  		minsz = offsetofend(struct vfio_iommu_type1_info, iova_pgsizes);
>  
> @@ -1959,6 +2023,34 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
>  
>  		info.iova_pgsizes = vfio_pgsize_bitmap(iommu);
>  
> +		if (info.argsz == minsz)
> +			goto done;

I don't think the above branch should exist, we want to tell the user
via argsz and flags that capabilities exist even if they only passed
the previous structure size through.

> +
> +		ret = vfio_build_iommu_iova_caps(iommu, &caps);
> +		if (ret)
> +			return ret;
> +
> +		if (caps.size) {
> +			info.flags |= VFIO_IOMMU_INFO_CAPS;
> +			minsz = offsetofend(struct vfio_iommu_type1_info,
> +							 cap_offset);

Only update minsz if this is within the provided argsz.

> +			if (info.argsz < sizeof(info) + caps.size) {
> +				info.argsz = sizeof(info) + caps.size;
> +				info.cap_offset = 0;

IOW, if cap_offset doesn't get copied to the user, that's ok, we've
provided them the flag and argsz they need to recognize it's there and
call with a sufficient buffer next time.

> +			} else {
> +				vfio_info_cap_shift(&caps, sizeof(info));
> +				if (copy_to_user((void __user *)arg +
> +						sizeof(info), caps.buf,
> +						caps.size)) {
> +					kfree(caps.buf);
> +					return -EFAULT;
> +				}
> +				info.cap_offset = sizeof(info);
> +			}
> +
> +			kfree(caps.buf);
> +		}
> +done:
>  		return copy_to_user((void __user *)arg, &info, minsz) ?
>  			-EFAULT : 0;
>  
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index c743721..46b49e9 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -589,7 +589,30 @@ struct vfio_iommu_type1_info {
>  	__u32	argsz;
>  	__u32	flags;
>  #define VFIO_IOMMU_INFO_PGSIZES (1 << 0)	/* supported page sizes info */
> +#define VFIO_IOMMU_INFO_CAPS	(1 << 1)	/* Info supports caps */
>  	__u64	iova_pgsizes;		/* Bitmap of supported page sizes */
> +	__u32   cap_offset;	/* Offset within info struct of first cap */
> +};
> +
> +/*
> + * The IOVA capability allows to report the valid IOVA range(s)
> + * excluding any reserved regions associated with dev group. Any dma
> + * map attempt outside the valid iova range will return error.
> + *
> + * The structures below define version 1 of this capability.
> + */
> +#define VFIO_IOMMU_TYPE1_INFO_CAP_IOVA_RANGE  1
> +
> +struct vfio_iova_range {
> +	__u64	start;
> +	__u64	end;
> +};
> +
> +struct vfio_iommu_type1_info_cap_iova_range {
> +	struct vfio_info_cap_header header;
> +	__u32	nr_iovas;
> +	__u32	reserved;
> +	struct vfio_iova_range iova_ranges[];
>  };
>  
>  #define VFIO_IOMMU_GET_INFO _IO(VFIO_TYPE, VFIO_BASE + 12)

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