diff options
author | Joao Martins <joao.m.martins@oracle.com> | 2022-09-08 21:34:42 +0300 |
---|---|---|
committer | Alex Williamson <alex.williamson@redhat.com> | 2022-09-08 21:59:00 +0300 |
commit | 58ccf0190d19d9a8a41f8a02b9e06742b58df4a1 (patch) | |
tree | 9647eae07a090e612ea0d38930b20877711eb3f6 /drivers | |
parent | 42ee53f9bfd3e4cf58ae7656e0d11075f5fe8489 (diff) | |
download | linux-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 'drivers')
-rw-r--r-- | drivers/vfio/Makefile | 6 | ||||
-rw-r--r-- | drivers/vfio/iova_bitmap.c | 422 |
2 files changed, 426 insertions, 2 deletions
diff --git a/drivers/vfio/Makefile b/drivers/vfio/Makefile index 1a32357592e3..d67c604d0407 100644 --- a/drivers/vfio/Makefile +++ b/drivers/vfio/Makefile @@ -1,9 +1,11 @@ # SPDX-License-Identifier: GPL-2.0 vfio_virqfd-y := virqfd.o -vfio-y += vfio_main.o - obj-$(CONFIG_VFIO) += vfio.o + +vfio-y += vfio_main.o \ + iova_bitmap.o \ + obj-$(CONFIG_VFIO_VIRQFD) += vfio_virqfd.o obj-$(CONFIG_VFIO_IOMMU_TYPE1) += vfio_iommu_type1.o obj-$(CONFIG_VFIO_IOMMU_SPAPR_TCE) += vfio_iommu_spapr_tce.o diff --git a/drivers/vfio/iova_bitmap.c b/drivers/vfio/iova_bitmap.c new file mode 100644 index 000000000000..6631e8befe1b --- /dev/null +++ b/drivers/vfio/iova_bitmap.c @@ -0,0 +1,422 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (c) 2022, Oracle and/or its affiliates. + * Copyright (c) 2022, NVIDIA CORPORATION & AFFILIATES. All rights reserved + */ +#include <linux/iova_bitmap.h> +#include <linux/mm.h> +#include <linux/highmem.h> + +#define BITS_PER_PAGE (PAGE_SIZE * BITS_PER_BYTE) + +/* + * struct iova_bitmap_map - A bitmap representing an IOVA range + * + * Main data structure for tracking mapped user pages of bitmap data. + * + * For example, for something recording dirty IOVAs, it will be provided a + * struct iova_bitmap structure, as a general structure for iterating the + * total IOVA range. The struct iova_bitmap_map, though, represents the + * subset of said IOVA space that is pinned by its parent structure (struct + * iova_bitmap). + * + * The user does not need to exact location of the bits in the bitmap. + * From user perspective the only API available is iova_bitmap_set() which + * records the IOVA *range* in the bitmap by setting the corresponding + * bits. + * + * The bitmap is an array of u64 whereas each bit represents an IOVA of + * range of (1 << pgshift). Thus formula for the bitmap data to be set is: + * + * data[(iova / page_size) / 64] & (1ULL << (iova % 64)) + */ +struct iova_bitmap_map { + /* base IOVA representing bit 0 of the first page */ + unsigned long iova; + + /* page size order that each bit granules to */ + unsigned long pgshift; + + /* page offset of the first user page pinned */ + unsigned long pgoff; + + /* number of pages pinned */ + unsigned long npages; + + /* pinned pages representing the bitmap data */ + struct page **pages; +}; + +/* + * struct iova_bitmap - The IOVA bitmap object + * + * Main data structure for iterating over the bitmap data. + * + * Abstracts the pinning work and iterates in IOVA ranges. + * It uses a windowing scheme and pins the bitmap in relatively + * big ranges e.g. + * + * The bitmap object uses one base page to store all the pinned pages + * pointers related to the bitmap. For sizeof(struct page*) == 8 it stores + * 512 struct page pointers which, if the base page size is 4K, it means + * 2M of bitmap data is pinned at a time. If the iova_bitmap page size is + * also 4K then the range window to iterate is 64G. + * + * For example iterating on a total IOVA range of 4G..128G, it will walk + * through this set of ranges: + * + * 4G - 68G-1 (64G) + * 68G - 128G-1 (64G) + * + * An example of the APIs on how to use/iterate over the IOVA bitmap: + * + * bitmap = iova_bitmap_alloc(iova, length, page_size, data); + * if (IS_ERR(bitmap)) + * return PTR_ERR(bitmap); + * + * 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 internals of the object uses an index @mapped_base_index that indexes + * which u64 word of the bitmap is mapped, up to @mapped_total_index. + * Those keep being incremented until @mapped_total_index is reached while + * mapping up to PAGE_SIZE / sizeof(struct page*) maximum of pages. + * + * The IOVA bitmap is usually located on what tracks DMA mapped ranges or + * some form of IOVA range tracking that co-relates to the user passed + * bitmap. + */ +struct iova_bitmap { + /* IOVA range representing the currently mapped bitmap data */ + struct iova_bitmap_map mapped; + + /* userspace address of the bitmap */ + u64 __user *bitmap; + + /* u64 index that @mapped points to */ + unsigned long mapped_base_index; + + /* how many u64 can we walk in total */ + unsigned long mapped_total_index; + + /* base IOVA of the whole bitmap */ + unsigned long iova; + + /* length of the IOVA range for the whole bitmap */ + size_t length; +}; + +/* + * Converts a relative IOVA to a bitmap index. + * This function provides the index into the u64 array (bitmap::bitmap) + * for a given IOVA offset. + * Relative IOVA means relative to the bitmap::mapped base IOVA + * (stored in mapped::iova). All computations in this file are done using + * relative IOVAs and thus avoid an extra subtraction against mapped::iova. + * The user API iova_bitmap_set() always uses a regular absolute IOVAs. + */ +static unsigned long iova_bitmap_offset_to_index(struct iova_bitmap *bitmap, + unsigned long iova) +{ + unsigned long pgsize = 1 << bitmap->mapped.pgshift; + + return iova / (BITS_PER_TYPE(*bitmap->bitmap) * pgsize); +} + +/* + * Converts a bitmap index to a *relative* IOVA. + */ +static unsigned long iova_bitmap_index_to_offset(struct iova_bitmap *bitmap, + unsigned long index) +{ + unsigned long pgshift = bitmap->mapped.pgshift; + + return (index * BITS_PER_TYPE(*bitmap->bitmap)) << pgshift; +} + +/* + * Returns the base IOVA of the mapped range. + */ +static unsigned long iova_bitmap_mapped_iova(struct iova_bitmap *bitmap) +{ + unsigned long skip = bitmap->mapped_base_index; + + return bitmap->iova + iova_bitmap_index_to_offset(bitmap, skip); +} + +/* + * Pins the bitmap user pages for the current range window. + * This is internal to IOVA bitmap and called when advancing the + * index (@mapped_base_index) or allocating the bitmap. + */ +static int iova_bitmap_get(struct iova_bitmap *bitmap) +{ + struct iova_bitmap_map *mapped = &bitmap->mapped; + unsigned long npages; + u64 __user *addr; + long ret; + + /* + * @mapped_base_index is the index of the currently mapped u64 words + * that we have access. Anything before @mapped_base_index is not + * mapped. The range @mapped_base_index .. @mapped_total_index-1 is + * mapped but capped at a maximum number of pages. + */ + npages = DIV_ROUND_UP((bitmap->mapped_total_index - + bitmap->mapped_base_index) * + sizeof(*bitmap->bitmap), PAGE_SIZE); + + /* + * We always cap at max number of 'struct page' a base page can fit. + * This is, for example, on x86 means 2M of bitmap data max. + */ + npages = min(npages, PAGE_SIZE / sizeof(struct page *)); + + /* + * Bitmap address to be pinned is calculated via pointer arithmetic + * with bitmap u64 word index. + */ + addr = bitmap->bitmap + bitmap->mapped_base_index; + + ret = pin_user_pages_fast((unsigned long)addr, npages, + FOLL_WRITE, mapped->pages); + if (ret <= 0) + return -EFAULT; + + mapped->npages = (unsigned long)ret; + /* Base IOVA where @pages point to i.e. bit 0 of the first page */ + mapped->iova = iova_bitmap_mapped_iova(bitmap); + + /* + * offset of the page where pinned pages bit 0 is located. + * This handles the case where the bitmap is not PAGE_SIZE + * aligned. + */ + mapped->pgoff = offset_in_page(addr); + return 0; +} + +/* + * Unpins the bitmap user pages and clears @npages + * (un)pinning is abstracted from API user and it's done when advancing + * the index or freeing the bitmap. + */ +static void iova_bitmap_put(struct iova_bitmap *bitmap) +{ + struct iova_bitmap_map *mapped = &bitmap->mapped; + + if (mapped->npages) { + unpin_user_pages(mapped->pages, mapped->npages); + mapped->npages = 0; + } +} + +/** + * iova_bitmap_alloc() - Allocates an IOVA bitmap object + * @iova: Start address of the IOVA range + * @length: Length of the IOVA range + * @page_size: Page size of the IOVA bitmap. It defines what each bit + * granularity represents + * @data: Userspace address of the bitmap + * + * Allocates an IOVA object and initializes all its fields including the + * first user pages of @data. + * + * Return: A pointer to a newly allocated struct iova_bitmap + * or ERR_PTR() on error. + */ +struct iova_bitmap *iova_bitmap_alloc(unsigned long iova, size_t length, + unsigned long page_size, u64 __user *data) +{ + struct iova_bitmap_map *mapped; + struct iova_bitmap *bitmap; + int rc; + + bitmap = kzalloc(sizeof(*bitmap), GFP_KERNEL); + if (!bitmap) + return ERR_PTR(-ENOMEM); + + mapped = &bitmap->mapped; + mapped->pgshift = __ffs(page_size); + bitmap->bitmap = data; + bitmap->mapped_total_index = + iova_bitmap_offset_to_index(bitmap, length - 1) + 1; + bitmap->iova = iova; + bitmap->length = length; + mapped->iova = iova; + mapped->pages = (struct page **)__get_free_page(GFP_KERNEL); + if (!mapped->pages) { + rc = -ENOMEM; + goto err; + } + + rc = iova_bitmap_get(bitmap); + if (rc) + goto err; + return bitmap; + +err: + iova_bitmap_free(bitmap); + return ERR_PTR(rc); +} + +/** + * iova_bitmap_free() - Frees an IOVA bitmap object + * @bitmap: IOVA bitmap to free + * + * It unpins and releases pages array memory and clears any leftover + * state. + */ +void iova_bitmap_free(struct iova_bitmap *bitmap) +{ + struct iova_bitmap_map *mapped = &bitmap->mapped; + + iova_bitmap_put(bitmap); + + if (mapped->pages) { + free_page((unsigned long)mapped->pages); + mapped->pages = NULL; + } + + kfree(bitmap); +} + +/* + * Returns the remaining bitmap indexes from mapped_total_index to process for + * the currently pinned bitmap pages. + */ +static unsigned long iova_bitmap_mapped_remaining(struct iova_bitmap *bitmap) +{ + unsigned long remaining; + + remaining = bitmap->mapped_total_index - bitmap->mapped_base_index; + remaining = min_t(unsigned long, remaining, + (bitmap->mapped.npages << PAGE_SHIFT) / sizeof(*bitmap->bitmap)); + + return remaining; +} + +/* + * Returns the length of the mapped IOVA range. + */ +static unsigned long iova_bitmap_mapped_length(struct iova_bitmap *bitmap) +{ + unsigned long max_iova = bitmap->iova + bitmap->length - 1; + unsigned long iova = iova_bitmap_mapped_iova(bitmap); + unsigned long remaining; + + /* + * iova_bitmap_mapped_remaining() returns a number of indexes which + * when converted to IOVA gives us a max length that the bitmap + * pinned data can cover. Afterwards, that is capped to + * only cover the IOVA range in @bitmap::iova .. @bitmap::length. + */ + remaining = iova_bitmap_index_to_offset(bitmap, + iova_bitmap_mapped_remaining(bitmap)); + + if (iova + remaining - 1 > max_iova) + remaining -= ((iova + remaining - 1) - max_iova); + + return remaining; +} + +/* + * Returns true if there's not more data to iterate. + */ +static bool iova_bitmap_done(struct iova_bitmap *bitmap) +{ + return bitmap->mapped_base_index >= bitmap->mapped_total_index; +} + +/* + * Advances to the next range, releases the current pinned + * pages and pins the next set of bitmap pages. + * Returns 0 on success or otherwise errno. + */ +static int iova_bitmap_advance(struct iova_bitmap *bitmap) +{ + unsigned long iova = iova_bitmap_mapped_length(bitmap) - 1; + unsigned long count = iova_bitmap_offset_to_index(bitmap, iova) + 1; + + bitmap->mapped_base_index += count; + + iova_bitmap_put(bitmap); + if (iova_bitmap_done(bitmap)) + return 0; + + /* When advancing the index we pin the next set of bitmap pages */ + return iova_bitmap_get(bitmap); +} + +/** + * iova_bitmap_for_each() - Iterates over the bitmap + * @bitmap: IOVA bitmap to iterate + * @opaque: Additional argument to pass to the callback + * @fn: Function that gets called for each IOVA range + * + * Helper function to iterate over bitmap data representing a portion of IOVA + * space. It hides the complexity of iterating bitmaps and translating the + * mapped bitmap user pages into IOVA ranges to process. + * + * Return: 0 on success, and an error on failure either upon + * iteration or when the callback returns an error. + */ +int iova_bitmap_for_each(struct iova_bitmap *bitmap, void *opaque, + iova_bitmap_fn_t fn) +{ + int ret = 0; + + for (; !iova_bitmap_done(bitmap) && !ret; + ret = iova_bitmap_advance(bitmap)) { + ret = fn(bitmap, iova_bitmap_mapped_iova(bitmap), + iova_bitmap_mapped_length(bitmap), opaque); + if (ret) + break; + } + + return ret; +} + +/** + * iova_bitmap_set() - Records an IOVA range in bitmap + * @bitmap: IOVA bitmap + * @iova: IOVA to start + * @length: IOVA range length + * + * Set the bits corresponding to the range [iova .. iova+length-1] in + * the user bitmap. + * + * Return: The number of bits set. + */ +void iova_bitmap_set(struct iova_bitmap *bitmap, + unsigned long iova, size_t length) +{ + struct iova_bitmap_map *mapped = &bitmap->mapped; + unsigned long offset = (iova - mapped->iova) >> mapped->pgshift; + unsigned long nbits = max_t(unsigned long, 1, length >> mapped->pgshift); + unsigned long page_idx = offset / BITS_PER_PAGE; + unsigned long page_offset = mapped->pgoff; + void *kaddr; + + offset = offset % BITS_PER_PAGE; + + do { + unsigned long size = min(BITS_PER_PAGE - offset, nbits); + + kaddr = kmap_local_page(mapped->pages[page_idx]); + bitmap_set(kaddr + page_offset, offset, size); + kunmap_local(kaddr); + page_offset = offset = 0; + nbits -= size; + page_idx++; + } while (nbits > 0); +} +EXPORT_SYMBOL_GPL(iova_bitmap_set); |