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Subject[RFC PATCH 05/10] vfio: Create a vfio_device from vma lookup
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Date
Introduce a vfio bus driver policy where using the exported
vfio_device_vma_open() as the vm_ops.open for a vma indicates
vm_private_data is the struct vfio_device pointer associated
to the vma. This allows a direct vma to device lookup.

Operating on an active, open vma to the device, we should be
able to directly increment the vfio_device reference.

Implemented only for vfio-pci for now.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
drivers/vfio/pci/vfio_pci.c | 6 ++++--
drivers/vfio/vfio.c | 24 ++++++++++++++++++++++++
include/linux/vfio.h | 2 ++
3 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 115f10f7b096..f9529bac6c97 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -1469,7 +1469,8 @@ void vfio_pci_memory_unlock_and_restore(struct vfio_pci_device *vdev, u16 cmd)
static vm_fault_t vfio_pci_mmap_fault(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
- struct vfio_pci_device *vdev = vma->vm_private_data;
+ struct vfio_device *device = vma->vm_private_data;
+ struct vfio_pci_device *vdev = vfio_device_data(device);
vm_fault_t ret = VM_FAULT_SIGBUS;

down_read(&vdev->memory_lock);
@@ -1485,6 +1486,7 @@ static vm_fault_t vfio_pci_mmap_fault(struct vm_fault *vmf)
}

static const struct vm_operations_struct vfio_pci_mmap_ops = {
+ .open = vfio_device_vma_open,
.fault = vfio_pci_mmap_fault,
};

@@ -1542,7 +1544,7 @@ static int vfio_pci_mmap(void *device_data, struct vm_area_struct *vma)
}
}

- vma->vm_private_data = vdev;
+ vma->vm_private_data = vdev->device;
vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
vma->vm_pgoff = (pci_resource_start(pdev, index) >> PAGE_SHIFT) + pgoff;

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index da212425ab30..399c42b77fbb 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -572,6 +572,15 @@ void vfio_device_unmap_mapping_range(struct vfio_device *device,
}
EXPORT_SYMBOL_GPL(vfio_device_unmap_mapping_range);

+/*
+ * A VFIO bus driver using this open callback will provide a
+ * struct vfio_device pointer in the vm_private_data field.
+ */
+void vfio_device_vma_open(struct vm_area_struct *vma)
+{
+}
+EXPORT_SYMBOL_GPL(vfio_device_vma_open);
+
/**
* Device objects - create, release, get, put, search
*/
@@ -927,6 +936,21 @@ struct vfio_device *vfio_device_get_from_dev(struct device *dev)
}
EXPORT_SYMBOL_GPL(vfio_device_get_from_dev);

+struct vfio_device *vfio_device_get_from_vma(struct vm_area_struct *vma)
+{
+ struct vfio_device *device;
+
+ if (vma->vm_ops->open != vfio_device_vma_open)
+ return ERR_PTR(-ENODEV);
+
+ device = vma->vm_private_data;
+
+ vfio_device_get(device);
+
+ return device;
+}
+EXPORT_SYMBOL_GPL(vfio_device_get_from_vma);
+
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 f435dfca15eb..188c2f3feed9 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -58,6 +58,8 @@ extern void vfio_device_put(struct vfio_device *device);
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 void vfio_device_vma_open(struct vm_area_struct *vma);
+extern struct vfio_device *vfio_device_get_from_vma(struct vm_area_struct *vma);

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