[PATCH 6/7] vfio: Add vfio_device_io_remap_mapping_range()

Alex Williamson
2021-08-05T17:08:22Z

This provides a mirror of vfio_device_unmap_mapping_range() for
vmas mapping device memory where the pfn is provided by
vfio_device_vma_to_pfn().

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
drivers/vfio/vfio.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
include/linux/vfio.h | 2 ++
2 files changed, 46 insertions(+)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 42ca93be152a..c5b3a3446dd9 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -33,6 +33,7 @@
#include <linux/uaccess.h>
#include <linux/vfio.h>
#include <linux/wait.h>
+#include <linux/sched/mm.h>
#include <linux/sched/signal.h>

#define DRIVER_VERSION "0.3"
@@ -567,6 +568,49 @@ void vfio_device_unmap_mapping_range(struct vfio_device *device,
}
EXPORT_SYMBOL_GPL(vfio_device_unmap_mapping_range);

+int vfio_device_io_remap_mapping_range(struct vfio_device *device,
+ loff_t start, loff_t len)
+{
+ struct address_space *mapping = device->inode->i_mapping;
+ int ret = 0;
+
+ i_mmap_lock_write(mapping);
+ if (mapping_mapped(mapping)) {
+ struct rb_root_cached *root = &mapping->i_mmap;
+ pgoff_t pgstart = start >> PAGE_SHIFT;
+ pgoff_t pgend = (start + len - 1) >> PAGE_SHIFT;
+ struct vm_area_struct *vma;
+
+ vma_interval_tree_foreach(vma, root, pgstart, pgend) {
+ unsigned long pfn;
+ unsigned int flags;
+
+ ret = vfio_device_vma_to_pfn(device, vma, &pfn);
+ if (ret)
+ break;
+
+ /*
+ * Force NOFS memory allocation context to avoid
+ * deadlock while we hold i_mmap_rwsem.
+ */
+ flags = memalloc_nofs_save();
+ ret = io_remap_pfn_range(vma, vma->vm_start, pfn,
+ vma->vm_end - vma->vm_start,
+ vma->vm_page_prot);
+ memalloc_nofs_restore(flags);
+ if (ret)
+ break;
+ }
+ }
+ i_mmap_unlock_write(mapping);
+
+ if (ret)
+ vfio_device_unmap_mapping_range(device, start, len);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(vfio_device_io_remap_mapping_range);
+
/**
* Device objects - create, release, get, put, search
*/
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 5f07ebe0f85d..c2c51c7a6f05 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -71,6 +71,8 @@ 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_io_remap_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);