linux-kernel - Re: [PATCH v4 05/10] vfio/fsl-mc: Allow userspace to MMAP fsl-mc device MMIO regions

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Date:   Thu, 3 Sep 2020 18:05:13 +0200
From:   Auger Eric <eric.auger@...hat.com>
To:     Diana Craciun <diana.craciun@....nxp.com>,
        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 v4 05/10] vfio/fsl-mc: Allow userspace to MMAP fsl-mc
 device MMIO regions

Hi Diana,

On 8/26/20 11:33 AM, 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>
> ---
>  drivers/vfio/fsl-mc/vfio_fsl_mc.c | 60 +++++++++++++++++++++++++++++--
>  1 file changed, 58 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/vfio/fsl-mc/vfio_fsl_mc.c b/drivers/vfio/fsl-mc/vfio_fsl_mc.c
> index 093b8d68496c..64d5c1fff51f 100644
> --- a/drivers/vfio/fsl-mc/vfio_fsl_mc.c
> +++ b/drivers/vfio/fsl-mc/vfio_fsl_mc.c
> @@ -33,7 +33,8 @@ static int vfio_fsl_mc_regions_init(struct vfio_fsl_mc_device *vdev)
>  
>  		vdev->regions[i].addr = res->start;
>  		vdev->regions[i].size = resource_size(res);
> -		vdev->regions[i].flags = 0;
> +		vdev->regions[i].flags = VFIO_REGION_INFO_FLAG_MMAP;
Is the region always mmappable or does it depend on the
mc_dev->regions[i].flags. Also on VFIO platform we checked some
alignment addr/size constraints.
> +		vdev->regions[i].type = mc_dev->regions[i].flags & IORESOURCE_BITS;
>  	}
>  
>  	vdev->num_regions = mc_dev->obj_desc.region_count;
> @@ -164,9 +165,64 @@ 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);
I see in fsl-mc-bus.c that IORESOURCE_CACHEABLE and IORESOURCE_MEM are
set on the regions flag?
> +	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 >= vdev->num_regions)
> +		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 = {
> 
Thanks

Eric