[PATCH 4/7] vfio,vfio-pci: Add vma to pfn callback

Alex Williamson
2021-08-05T17:07:59Z

Add a new vfio_device_ops callback to allow the vfio device driver to
translate a vma mapping of a vfio device fd to a pfn. Implementation
limited to vfio-pci here for the purpose of supporting the reverse of
unmap_mapping_range(), but expected to be implemented for all vfio
device drivers supporting DMA mapping of device memory mmaps.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
drivers/vfio/pci/vfio_pci.c | 9 ++++++---
drivers/vfio/vfio.c | 18 ++++++++++++++++--
include/linux/vfio.h | 6 ++++++
3 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index c526edbf1173..7a9f67cfc0a2 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -1440,10 +1440,12 @@ void vfio_pci_memory_unlock_and_restore(struct vfio_pci_device *vdev, u16 cmd)
up_write(&vdev->memory_lock);
}

-static int vfio_pci_bar_vma_to_pfn(struct vm_area_struct *vma,
+static int vfio_pci_bar_vma_to_pfn(struct vfio_device *core_vdev,
+ struct vm_area_struct *vma,
unsigned long *pfn)
{
- struct vfio_pci_device *vdev = vma->vm_private_data;
+ struct vfio_pci_device *vdev =
+ container_of(core_vdev, struct vfio_pci_device, vdev);
struct pci_dev *pdev = vdev->pdev;
int index;
u64 pgoff;
@@ -1469,7 +1471,7 @@ static vm_fault_t vfio_pci_mmap_fault(struct vm_fault *vmf)
unsigned long vaddr, pfn;
vm_fault_t ret = VM_FAULT_SIGBUS;

- if (vfio_pci_bar_vma_to_pfn(vma, &pfn))
+ if (vfio_pci_bar_vma_to_pfn(&vdev->vdev, vma, &pfn))
return ret;

down_read(&vdev->memory_lock);
@@ -1742,6 +1744,7 @@ 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 1e4fc69fee7d..42ca93be152a 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -875,6 +875,22 @@ struct vfio_device *vfio_device_get_from_dev(struct device *dev)
}
EXPORT_SYMBOL_GPL(vfio_device_get_from_dev);

+static const struct file_operations vfio_device_fops;
+
+int vfio_device_vma_to_pfn(struct vfio_device *device,
+ struct vm_area_struct *vma, unsigned long *pfn)
+{
+ if (WARN_ON(!vma->vm_file || vma->vm_file->f_op != &vfio_device_fops ||
+ vma->vm_file->private_data != device))
+ return -EINVAL;
+
+ if (unlikely(!device->ops->vma_to_pfn))
+ return -EPERM;
+
+ return device->ops->vma_to_pfn(device, vma, pfn);
+}
+EXPORT_SYMBOL_GPL(vfio_device_vma_to_pfn);
+
static struct vfio_device *vfio_device_get_from_name(struct vfio_group *group,
char *buf)
{
@@ -1407,8 +1423,6 @@ static int vfio_group_add_container_user(struct vfio_group *group)
return 0;
}

-static const struct file_operations vfio_device_fops;
-
static int vfio_group_get_device_fd(struct vfio_group *group, char *buf)
{
struct vfio_device *device;
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 712813703e5a..5f07ebe0f85d 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -41,6 +41,7 @@ struct vfio_device {
* @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;
@@ -55,6 +56,8 @@ struct vfio_device_ops {
int (*mmap)(struct vfio_device *vdev, struct vm_area_struct *vma);
void (*request)(struct vfio_device *vdev, unsigned int count);
int (*match)(struct vfio_device *vdev, char *buf);
+ int (*vma_to_pfn)(struct vfio_device *vdev,
+ struct vm_area_struct *vma, unsigned long *pfn);
};

extern struct iommu_group *vfio_iommu_group_get(struct device *dev);
@@ -68,6 +71,9 @@ extern struct vfio_device *vfio_device_get_from_dev(struct device *dev);
extern void vfio_device_put(struct vfio_device *device);
extern void vfio_device_unmap_mapping_range(struct vfio_device *device,
loff_t start, loff_t len);
+extern int vfio_device_vma_to_pfn(struct vfio_device *device,
+ struct vm_area_struct *vma,
+ unsigned long *pfn);

/* events for the backend driver notify callback */
enum vfio_iommu_notify_type {