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authorJoao Martins <joao.m.martins@oracle.com>2022-09-08 21:34:42 +0300
committerAlex Williamson <alex.williamson@redhat.com>2022-09-08 21:59:00 +0300
commit58ccf0190d19d9a8a41f8a02b9e06742b58df4a1 (patch)
tree9647eae07a090e612ea0d38930b20877711eb3f6 /include/linux/iova_bitmap.h
parent42ee53f9bfd3e4cf58ae7656e0d11075f5fe8489 (diff)
downloadlinux-58ccf0190d19d9a8a41f8a02b9e06742b58df4a1.tar.xz
vfio: Add an IOVA bitmap support
The new facility adds a bunch of wrappers that abstract how an IOVA range is represented in a bitmap that is granulated by a given page_size. So it translates all the lifting of dealing with user pointers into its corresponding kernel addresses backing said user memory into doing finally the (non-atomic) bitmap ops to change various bits. The formula for the bitmap is: data[(iova / page_size) / 64] & (1ULL << (iova % 64)) Where 64 is the number of bits in a unsigned long (depending on arch) It introduces an IOVA iterator that uses a windowing scheme to minimize the pinning overhead, as opposed to pinning it on demand 4K at a time. Assuming a 4K kernel page and 4K requested page size, we can use a single kernel page to hold 512 page pointers, mapping 2M of bitmap, representing 64G of IOVA space. An example usage of these helpers for a given @base_iova, @page_size, @length and __user @data: bitmap = iova_bitmap_alloc(base_iova, page_size, length, data); if (IS_ERR(bitmap)) return -ENOMEM; ret = iova_bitmap_for_each(bitmap, arg, dirty_reporter_fn); iova_bitmap_free(bitmap); Each iteration of the @dirty_reporter_fn is called with a unique @iova and @length argument, indicating the current range available through the iova_bitmap. The @dirty_reporter_fn uses iova_bitmap_set() to mark dirty areas (@iova_length) within that provided range, as following: iova_bitmap_set(bitmap, iova, iova_length); The facility is intended to be used for user bitmaps representing dirtied IOVAs by IOMMU (via IOMMUFD) and PCI Devices (via vfio-pci). Signed-off-by: Joao Martins <joao.m.martins@oracle.com> Signed-off-by: Yishai Hadas <yishaih@nvidia.com> Link: https://lore.kernel.org/r/20220908183448.195262-5-yishaih@nvidia.com Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Diffstat (limited to 'include/linux/iova_bitmap.h')
-rw-r--r--include/linux/iova_bitmap.h26
1 files changed, 26 insertions, 0 deletions
diff --git a/include/linux/iova_bitmap.h b/include/linux/iova_bitmap.h
new file mode 100644
index 000000000000..c006cf0a25f3
--- /dev/null
+++ b/include/linux/iova_bitmap.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2022, Oracle and/or its affiliates.
+ * Copyright (c) 2022, NVIDIA CORPORATION & AFFILIATES. All rights reserved
+ */
+#ifndef _IOVA_BITMAP_H_
+#define _IOVA_BITMAP_H_
+
+#include <linux/types.h>
+
+struct iova_bitmap;
+
+typedef int (*iova_bitmap_fn_t)(struct iova_bitmap *bitmap,
+ unsigned long iova, size_t length,
+ void *opaque);
+
+struct iova_bitmap *iova_bitmap_alloc(unsigned long iova, size_t length,
+ unsigned long page_size,
+ u64 __user *data);
+void iova_bitmap_free(struct iova_bitmap *bitmap);
+int iova_bitmap_for_each(struct iova_bitmap *bitmap, void *opaque,
+ iova_bitmap_fn_t fn);
+void iova_bitmap_set(struct iova_bitmap *bitmap,
+ unsigned long iova, size_t length);
+
+#endif