From 58ccf0190d19d9a8a41f8a02b9e06742b58df4a1 Mon Sep 17 00:00:00 2001 From: Joao Martins Date: Thu, 8 Sep 2022 21:34:42 +0300 Subject: 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 Signed-off-by: Yishai Hadas Link: https://lore.kernel.org/r/20220908183448.195262-5-yishaih@nvidia.com Signed-off-by: Alex Williamson --- include/linux/iova_bitmap.h | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) create mode 100644 include/linux/iova_bitmap.h (limited to 'include/linux') 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 + +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 -- cgit v1.2.3