From: Joao Martins <joao.m.martins@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Yishai Hadas <yishaih@xxxxxxxxxx>
---
drivers/vfio/Makefile | 6 +-
drivers/vfio/iova_bitmap.c | 422 ++++++++++++++++++++++++++++++++++++
include/linux/iova_bitmap.h | 26 +++
3 files changed, 452 insertions(+), 2 deletions(-)
create mode 100644 drivers/vfio/iova_bitmap.c
create mode 100644 include/linux/iova_bitmap.h
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);
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
--
2.18.1
