linux-kernel - Re: [PATCH v6 05/10] vfio/fsl-mc: Allow userspace to MMAP fsl-mc device MMIO regions

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Date:   Sat, 10 Oct 2020 19:12:50 +0200
From:   Auger Eric <eric.auger@...hat.com>
To:     Diana Craciun <diana.craciun@....nxp.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, bharatb.linux@...il.com,
        laurentiu.tudor@....com, Bharat Bhushan <Bharat.Bhushan@....com>
Subject: Re: [PATCH v6 05/10] vfio/fsl-mc: Allow userspace to MMAP fsl-mc
 device MMIO regions

Hi Diana,

On 10/5/20 7:36 PM, Diana Craciun wrote:
> Allow userspace to mmap device regions for direct access of
> fsl-mc devices.
> 
> Signed-off-by: Bharat Bhushan <Bharat.Bhushan@....com>
> Signed-off-by: Diana Craciun <diana.craciun@....nxp.com>
Reviewed-by: Eric Auger <eric.auger@...hat.com>

Thanks

Eric

> ---
>  drivers/vfio/fsl-mc/vfio_fsl_mc.c | 68 ++++++++++++++++++++++++++++++-
>  1 file changed, 66 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/vfio/fsl-mc/vfio_fsl_mc.c b/drivers/vfio/fsl-mc/vfio_fsl_mc.c
> index 05dace5ddc2c..55190a2730fb 100644
> --- a/drivers/vfio/fsl-mc/vfio_fsl_mc.c
> +++ b/drivers/vfio/fsl-mc/vfio_fsl_mc.c
> @@ -30,11 +30,20 @@ static int vfio_fsl_mc_regions_init(struct vfio_fsl_mc_device *vdev)
>  
>  	for (i = 0; i < count; i++) {
>  		struct resource *res = &mc_dev->regions[i];
> +		int no_mmap = is_fsl_mc_bus_dprc(mc_dev);
>  
>  		vdev->regions[i].addr = res->start;
>  		vdev->regions[i].size = resource_size(res);
> -		vdev->regions[i].flags = 0;
>  		vdev->regions[i].type = mc_dev->regions[i].flags & IORESOURCE_BITS;
> +		/*
> +		 * Only regions addressed with PAGE granularity may be
> +		 * MMAPed securely.
> +		 */
> +		if (!no_mmap && !(vdev->regions[i].addr & ~PAGE_MASK) &&
> +				!(vdev->regions[i].size & ~PAGE_MASK))
> +			vdev->regions[i].flags |=
> +					VFIO_REGION_INFO_FLAG_MMAP;
> +
>  	}
>  
>  	return 0;
> @@ -163,9 +172,64 @@ static ssize_t vfio_fsl_mc_write(void *device_data, const char __user *buf,
>  	return -EINVAL;
>  }
>  
> +static int vfio_fsl_mc_mmap_mmio(struct vfio_fsl_mc_region region,
> +				 struct vm_area_struct *vma)
> +{
> +	u64 size = vma->vm_end - vma->vm_start;
> +	u64 pgoff, base;
> +	u8 region_cacheable;
> +
> +	pgoff = vma->vm_pgoff &
> +		((1U << (VFIO_FSL_MC_OFFSET_SHIFT - PAGE_SHIFT)) - 1);
> +	base = pgoff << PAGE_SHIFT;
> +
> +	if (region.size < PAGE_SIZE || base + size > region.size)
> +		return -EINVAL;
> +
> +	region_cacheable = (region.type & FSL_MC_REGION_CACHEABLE) &&
> +			   (region.type & FSL_MC_REGION_SHAREABLE);
> +	if (!region_cacheable)
> +		vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
> +
> +	vma->vm_pgoff = (region.addr >> PAGE_SHIFT) + pgoff;
> +
> +	return remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
> +			       size, vma->vm_page_prot);
> +}
> +
>  static int vfio_fsl_mc_mmap(void *device_data, struct vm_area_struct *vma)
>  {
> -	return -EINVAL;
> +	struct vfio_fsl_mc_device *vdev = device_data;
> +	struct fsl_mc_device *mc_dev = vdev->mc_dev;
> +	int index;
> +
> +	index = vma->vm_pgoff >> (VFIO_FSL_MC_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;
> +	if (!(vma->vm_flags & VM_SHARED))
> +		return -EINVAL;
> +	if (index >= mc_dev->obj_desc.region_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 = mc_dev;
> +
> +	return vfio_fsl_mc_mmap_mmio(vdev->regions[index], vma);
>  }
>  
>  static const struct vfio_device_ops vfio_fsl_mc_ops = {
>