Re: [PATCH v1 06/14] vfio: Add vma to pfn callback

[Jason Gunthorpe]

On Mon, Mar 08, 2021 at 02:48:16PM -0700, Alex Williamson wrote:
> Add a new vfio_device_ops callback to allow the bus driver to
> translate a vma mapping of a vfio device fd to a pfn.  Plumb through
> vfio-core.  Implemented for vfio-pci.
> 
> Suggested-by: Jason Gunthorpe 
> Signed-off-by: Alex Williamson 
>  drivers/vfio/pci/vfio_pci.c |1 +
>  drivers/vfio/vfio.c |   16 
>  include/linux/vfio.h|3 +++
>  3 files changed, 20 insertions(+)
> 
> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> index 415b5109da9b..585895970e9c 100644
> +++ b/drivers/vfio/pci/vfio_pci.c
> @@ -1756,6 +1756,7 @@ static const struct vfio_device_ops vfio_pci_ops = {
>   .mmap   = vfio_pci_mmap,
>   .request= vfio_pci_request,
>   .match  = vfio_pci_match,
> + .vma_to_pfn = vfio_pci_bar_vma_to_pfn,
>  };
>  
>  static int vfio_pci_reflck_attach(struct vfio_pci_device *vdev);
> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> index 3a3e85a0dc3e..c47895539a1a 100644
> +++ b/drivers/vfio/vfio.c
> @@ -944,6 +944,22 @@ struct vfio_device *vfio_device_get_from_vma(struct 
> vm_area_struct *vma)
>  }
>  EXPORT_SYMBOL_GPL(vfio_device_get_from_vma);
>  
> +int vfio_vma_to_pfn(struct vm_area_struct *vma, unsigned long *pfn)
> +{
> + struct vfio_device *device;
> +
> + if (!vma->vm_file || vma->vm_file->f_op != _device_fops)
> + return -EINVAL;
> +
> + device = vma->vm_file->private_data;

Since the caller has the vfio_device already I would pass in the
vfio_device here rather than look it up again.

If you are really worried about API mis-use then use a protective
assertion like this:

  if (WARN_ON(vma->vm_file->private_data != device))
return -EINVAL;

Jason

[PATCH v1 06/14] vfio: Add vma to pfn callback

[Alex Williamson]

Add a new vfio_device_ops callback to allow the bus driver to
translate a vma mapping of a vfio device fd to a pfn.  Plumb through
vfio-core.  Implemented for vfio-pci.

Suggested-by: Jason Gunthorpe 
Signed-off-by: Alex Williamson 
---
 drivers/vfio/pci/vfio_pci.c |1 +
 drivers/vfio/vfio.c |   16 
 include/linux/vfio.h|3 +++
 3 files changed, 20 insertions(+)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 415b5109da9b..585895970e9c 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -1756,6 +1756,7 @@ static const struct vfio_device_ops vfio_pci_ops = {
.mmap   = vfio_pci_mmap,
.request= vfio_pci_request,
.match  = vfio_pci_match,
+   .vma_to_pfn = vfio_pci_bar_vma_to_pfn,
 };
 
 static int vfio_pci_reflck_attach(struct vfio_pci_device *vdev);
diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 3a3e85a0dc3e..c47895539a1a 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -944,6 +944,22 @@ struct vfio_device *vfio_device_get_from_vma(struct 
vm_area_struct *vma)
 }
 EXPORT_SYMBOL_GPL(vfio_device_get_from_vma);
 
+int vfio_vma_to_pfn(struct vm_area_struct *vma, unsigned long *pfn)
+{
+   struct vfio_device *device;
+
+   if (!vma->vm_file || vma->vm_file->f_op != _device_fops)
+   return -EINVAL;
+
+   device = vma->vm_file->private_data;
+
+   if (unlikely(!device->ops->vma_to_pfn))
+   return -EINVAL;
+
+   return device->ops->vma_to_pfn(vma, pfn);
+}
+EXPORT_SYMBOL_GPL(vfio_vma_to_pfn);
+
 static struct vfio_device *vfio_device_get_from_name(struct vfio_group *group,
 char *buf)
 {
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 660b8adf90a6..dbd90d0ba713 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -29,6 +29,7 @@
  * @match: Optional device name match callback (return: 0 for no-match, >0 for
  * match, -errno for abort (ex. match with insufficient or incorrect
  * additional args)
+ * @vma_to_pfn: Optional pfn from vma lookup against vma mapping device fd
  */
 struct vfio_device_ops {
char*name;
@@ -43,6 +44,7 @@ struct vfio_device_ops {
int (*mmap)(void *device_data, struct vm_area_struct *vma);
void(*request)(void *device_data, unsigned int count);
int (*match)(void *device_data, char *buf);
+   int (*vma_to_pfn)(struct vm_area_struct *vma, unsigned long *pfn);
 };
 
 extern struct iommu_group *vfio_iommu_group_get(struct device *dev);
@@ -59,6 +61,7 @@ extern void *vfio_device_data(struct vfio_device *device);
 extern void vfio_device_unmap_mapping_range(struct vfio_device *device,
loff_t start, loff_t len);
 extern struct vfio_device *vfio_device_get_from_vma(struct vm_area_struct 
*vma);
+extern int vfio_vma_to_pfn(struct vm_area_struct *vma, unsigned long *pfn);
 
 /* events for the backend driver notify callback */
 enum vfio_iommu_notify_type {