// 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/highmem.h>
#include <linux/iova_bitmap.h>
#include <linux/mm.h>
#include <linux/slab.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;
/* mapped length */
unsigned long length;
/* 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 */
u8 __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);
}
static unsigned long iova_bitmap_mapped_length(struct iova_bitmap *bitmap);
/*
* 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;
u8 __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);
/*
* Bitmap address to be pinned is calculated via pointer arithmetic
* with bitmap u64 word index.
*/
addr = bitmap->bitmap + bitmap->mapped_base_index;
/*
* 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 + !!offset_in_page(addr),
PAGE_SIZE / sizeof(struct page *));
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);
mapped->length = iova_bitmap_mapped_length(bitmap);
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 = (u8 __user *)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;
}
return bitmap;
err:
iova_bitmap_free(bitmap);
return ERR_PTR(rc);
}
EXPORT_SYMBOL_NS_GPL(iova_bitmap_alloc, IOMMUFD);
/**
* 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);
}
EXPORT_SYMBOL_NS_GPL(iova_bitmap_free, IOMMUFD);
/*
* 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, bytes;
bytes = (bitmap->mapped.npages << PAGE_SHIFT) - bitmap->mapped.pgoff;
remaining = bitmap->mapped_total_index - bitmap->mapped_base_index;
remaining = min_t(unsigned long, remaining,
DIV_ROUND_UP(bytes, 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 [@iova..@iova+@length-1] is part of the mapped IOVA range.
*/
static bool iova_bitmap_mapped_range(struct iova_bitmap_map *mapped,
unsigned long iova, size_t length)
{
return mapped->npages &&
(iova >= mapped->iova &&
(iova + length - 1) <= (mapped->iova + mapped->length - 1));
}
/*
* Advances to a selected 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_to(struct iova_bitmap *bitmap,
unsigned long iova)
{
unsigned long index;
index = iova_bitmap_offset_to_index(bitmap, iova - bitmap->iova);
if (index >= bitmap->mapped_total_index)
return -EINVAL;
bitmap->mapped_base_index = index;
iova_bitmap_put(bitmap);
/* 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)
{
return fn(bitmap, bitmap->iova, bitmap->length, opaque);
}
EXPORT_SYMBOL_NS_GPL(iova_bitmap_for_each, IOMMUFD);
/**
* 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.
*
*/
void iova_bitmap_set(struct iova_bitmap *bitmap,
unsigned long iova, size_t length)
{
struct iova_bitmap_map *mapped = &bitmap->mapped;
unsigned long cur_bit, last_bit, last_page_idx;
update_indexes:
if (unlikely(!iova_bitmap_mapped_range(mapped, iova, length))) {
/*
* The attempt to advance the base index to @iova
* may fail if it's out of bounds, or pinning the pages
* returns an error.
*/
if (iova_bitmap_advance_to(bitmap, iova))
return;
}
last_page_idx = mapped->npages - 1;
cur_bit = ((iova - mapped->iova) >>
mapped->pgshift) + mapped->pgoff * BITS_PER_BYTE;
last_bit = (((iova + length - 1) - mapped->iova) >>
mapped->pgshift) + mapped->pgoff * BITS_PER_BYTE;
do {
unsigned int page_idx = cur_bit / BITS_PER_PAGE;
unsigned int offset = cur_bit % BITS_PER_PAGE;
unsigned int nbits = min(BITS_PER_PAGE - offset,
last_bit - cur_bit + 1);
void *kaddr;
if (unlikely(page_idx > last_page_idx)) {
unsigned long left =
((last_bit - cur_bit + 1) << mapped->pgshift);
iova += (length - left);
length = left;
goto update_indexes;
}
kaddr = kmap_local_page(mapped->pages[page_idx]);
bitmap_set(kaddr, offset, nbits);
kunmap_local(kaddr);
cur_bit += nbits;
} while (cur_bit <= last_bit);
}
EXPORT_SYMBOL_NS_GPL(iova_bitmap_set, IOMMUFD);
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