linux-kernel - Re: [PATCH v9 06/12] vfio_pci: Update vfio_pci to use vfio_info_add

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Date:   Thu, 20 Oct 2016 13:24:54 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Kirti Wankhede <kwankhede@...dia.com>
Cc:     <pbonzini@...hat.com>, <kraxel@...hat.com>, <cjia@...dia.com>,
        <qemu-devel@...gnu.org>, <kvm@...r.kernel.org>,
        <kevin.tian@...el.com>, <jike.song@...el.com>,
        <bjsdjshi@...ux.vnet.ibm.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 06/12] vfio_pci: Update vfio_pci to use
 vfio_info_add_capability()

On Tue, 18 Oct 2016 02:52:06 +0530
Kirti Wankhede <kwankhede@...dia.com> wrote:

> Update msix_sparse_mmap_cap() to use vfio_info_add_capability()
> Update region type capability to use vfio_info_add_capability()
> Can't split this commit for MSIx and region_type cap since there is a
> common code which need to be updated for both the cases.
> 
> Signed-off-by: Kirti Wankhede <kwankhede@...dia.com>
> Signed-off-by: Neo Jia <cjia@...dia.com>
> Change-Id: I52bb28c7875a6da5a79ddad1843e6088aff58a45
> ---
>  drivers/vfio/pci/vfio_pci.c | 72 +++++++++++++++++----------------------------
>  1 file changed, 27 insertions(+), 45 deletions(-)
> 
> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> index d624a527777f..1ec0565b48ea 100644
> --- a/drivers/vfio/pci/vfio_pci.c
> +++ b/drivers/vfio/pci/vfio_pci.c
> @@ -556,12 +556,12 @@ static int vfio_pci_for_each_slot_or_bus(struct pci_dev *pdev,
>  }
>  
>  static int msix_sparse_mmap_cap(struct vfio_pci_device *vdev,
> +				struct vfio_region_info *info,
>  				struct vfio_info_cap *caps)
>  {
> -	struct vfio_info_cap_header *header;
>  	struct vfio_region_info_cap_sparse_mmap *sparse;
>  	size_t end, size;
> -	int nr_areas = 2, i = 0;
> +	int nr_areas = 2, i = 0, ret;
>  
>  	end = pci_resource_len(vdev->pdev, vdev->msix_bar);
>  
> @@ -572,13 +572,10 @@ static int msix_sparse_mmap_cap(struct vfio_pci_device *vdev,
>  
>  	size = sizeof(*sparse) + (nr_areas * sizeof(*sparse->areas));
>  
> -	header = vfio_info_cap_add(caps, size,
> -				   VFIO_REGION_INFO_CAP_SPARSE_MMAP, 1);
> -	if (IS_ERR(header))
> -		return PTR_ERR(header);
> +	sparse = kzalloc(size, GFP_KERNEL);
> +	if (!sparse)
> +		return -ENOMEM;
>  
> -	sparse = container_of(header,
> -			      struct vfio_region_info_cap_sparse_mmap, header);
>  	sparse->nr_areas = nr_areas;
>  
>  	if (vdev->msix_offset & PAGE_MASK) {
> @@ -594,26 +591,11 @@ static int msix_sparse_mmap_cap(struct vfio_pci_device *vdev,
>  		i++;
>  	}
>  
> -	return 0;
> -}
> -
> -static int region_type_cap(struct vfio_pci_device *vdev,
> -			   struct vfio_info_cap *caps,
> -			   unsigned int type, unsigned int subtype)
> -{
> -	struct vfio_info_cap_header *header;
> -	struct vfio_region_info_cap_type *cap;
> -
> -	header = vfio_info_cap_add(caps, sizeof(*cap),
> -				   VFIO_REGION_INFO_CAP_TYPE, 1);
> -	if (IS_ERR(header))
> -		return PTR_ERR(header);
> +	ret = vfio_info_add_capability(info, caps,
> +				      VFIO_REGION_INFO_CAP_SPARSE_MMAP, sparse);
> +	kfree(sparse);
>  
> -	cap = container_of(header, struct vfio_region_info_cap_type, header);
> -	cap->type = type;
> -	cap->subtype = subtype;
> -
> -	return 0;
> +	return ret;
>  }
>  
>  int vfio_pci_register_dev_region(struct vfio_pci_device *vdev,
> @@ -704,7 +686,8 @@ static long vfio_pci_ioctl(void *device_data,
>  			if (vdev->bar_mmap_supported[info.index]) {
>  				info.flags |= VFIO_REGION_INFO_FLAG_MMAP;
>  				if (info.index == vdev->msix_bar) {
> -					ret = msix_sparse_mmap_cap(vdev, &caps);
> +					ret = msix_sparse_mmap_cap(vdev, &info,
> +								   &caps);
>  					if (ret)
>  						return ret;
>  				}
> @@ -752,6 +735,9 @@ static long vfio_pci_ioctl(void *device_data,
>  
>  			break;
>  		default:
> +		{
> +			struct vfio_region_info_cap_type cap_type;
> +
>  			if (info.index >=
>  			    VFIO_PCI_NUM_REGIONS + vdev->num_regions)
>  				return -EINVAL;
> @@ -762,27 +748,23 @@ static long vfio_pci_ioctl(void *device_data,
>  			info.size = vdev->region[i].size;
>  			info.flags = vdev->region[i].flags;
>  
> -			ret = region_type_cap(vdev, &caps,
> -					      vdev->region[i].type,
> -					      vdev->region[i].subtype);
> +			cap_type.type = vdev->region[i].type;
> +			cap_type.subtype = vdev->region[i].subtype;
> +
> +			ret = vfio_info_add_capability(&info, &caps,
> +						      VFIO_REGION_INFO_CAP_TYPE,
> +						      &cap_type);
>  			if (ret)
>  				return ret;
> +
> +		}
>  		}
>  
> -		if (caps.size) {
> -			info.flags |= VFIO_REGION_INFO_FLAG_CAPS;
> -			if (info.argsz < sizeof(info) + caps.size) {
> -				info.argsz = sizeof(info) + caps.size;
> -				info.cap_offset = 0;
> -			} 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);

I prefer the case above, I'm fine with breaking out helpers to build a
buffer containing the capability chain, but I would rather have the
caller manage placing that back into the return structure.  That also
allows the helper to be independent of the structure we're operating
on, it could be a region_info, irq_info, device_info, etc.  It only
needs to know the layout of the capability type we're trying to add,
not the info structure itself.  Thanks,

Alex

> +		if (info.cap_offset) {
> +			if (copy_to_user((void __user *)arg + info.cap_offset,
> +					 caps.buf, caps.size)) {
> +				kfree(caps.buf);
> +				return -EFAULT;
>  			}
>  
>  			kfree(caps.buf);