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/*
* Copyright (c) 2019 Nutanix Inc. All rights reserved.
*
* Authors: Mike Cui <cui@nutanix.com>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of Nutanix nor the names of its contributors may be
* used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
* DAMAGE.
*
*/
#ifndef LIB_VFIO_USER_DMA_H
#define LIB_VFIO_USER_DMA_H
/*
* FIXME check whether DMA regions must be page aligned. If so then the
* implementation can be greatly simpified.
*/
/*
* This library emulates a DMA controller for a device emulation application to
* perform DMA operations on a foreign memory space.
*
* Concepts:
* - A DMA controller has its own 64-bit DMA address space.
* - Foreign memory is made available to the DMA controller in linear chunks
* called memory regions.
* - Each memory region is backed by a file descriptor and
* is registered with the DMA controllers at a unique, non-overlapping
* linear span of the DMA address space.
* - To perform DMA, the application should first build a scatter-gather
* list (sglist) of dma_sg_t from DMA addresses. Then the sglist
* can be mapped using dma_map_sg() into the process's virtual address space
* as an iovec for direct access, and unmapped using dma_unmap_sg() when done.
* Every region is mapped into the application's virtual address space
* at registration time with R/W permissions.
* dma_map_sg() ignores all protection bits and only does lookups and
* returns pointers to the previously mapped regions. dma_unmap_sg() is
* effectively a no-op.
*/
#ifdef DMA_MAP_PROTECTED
#undef DMA_MAP_FAST
#define DMA_MAP_FAST_IMPL 0
#else
#define DMA_MAP_FAST_IMPL 1
#endif
#include <assert.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <sys/mman.h>
#include <stdint.h>
#include <stdlib.h>
#include <limits.h>
#include <errno.h>
#include "libvfio-user.h"
#include "common.h"
#define iov_end(iov) ((iov)->iov_base + (iov)->iov_len)
struct vfu_ctx;
typedef struct {
vfu_dma_info_t info;
int fd; // File descriptor to mmap
off_t offset; // File offset
int refcnt; // Number of users of this region
char *dirty_bitmap; // Dirty page bitmap
} dma_memory_region_t;
typedef struct {
int max_regions;
int nregions;
struct vfu_ctx *vfu_ctx;
size_t dirty_pgsize; // Dirty page granularity
dma_memory_region_t regions[0];
} dma_controller_t;
dma_controller_t *
dma_controller_create(vfu_ctx_t *vfu_ctx, int max_regions);
void
dma_controller_remove_regions(dma_controller_t *dma);
void
dma_controller_destroy(dma_controller_t *dma);
/* Registers a new memory region.
* Returns:
* - On success, a non-negative region number
* - On failure, a negative integer (-x - 1) where x is the region number
* where this region would have been mapped to if the call could succeed
* (e.g. due to conflict with existing region).
*/
MOCK_DECLARE(int, dma_controller_add_region, dma_controller_t *dma,
vfu_dma_addr_t dma_addr, size_t size, int fd, off_t offset,
uint32_t prot);
MOCK_DECLARE(int, dma_controller_remove_region, dma_controller_t *dma,
vfu_dma_addr_t dma_addr, size_t size,
vfu_dma_unregister_cb_t *dma_unregister, void *data);
MOCK_DECLARE(void, dma_controller_unmap_region, dma_controller_t *dma,
dma_memory_region_t *region);
// Helper for dma_addr_to_sg() slow path.
int
_dma_addr_sg_split(const dma_controller_t *dma,
vfu_dma_addr_t dma_addr, uint32_t len,
dma_sg_t *sg, int max_sg, int prot);
static bool
_dma_should_mark_dirty(const dma_controller_t *dma, int prot)
{
assert(dma != NULL);
return (prot & PROT_WRITE) == PROT_WRITE && dma->dirty_pgsize > 0;
}
static size_t
_get_pgstart(size_t pgsize, void *base_addr, uint64_t offset)
{
return (offset - (uint64_t)base_addr) / pgsize;
}
static size_t
_get_pgend(size_t pgsize, uint64_t len, size_t start)
{
return start + (len / pgsize) + (len % pgsize != 0) - 1;
}
static void
_dma_bitmap_get_pgrange(const dma_controller_t *dma,
const dma_memory_region_t *region,
const dma_sg_t *sg, size_t *start, size_t *end)
{
assert(dma != NULL);
assert(region != NULL);
assert(sg != NULL);
assert(start != NULL);
assert(end != NULL);
*start = _get_pgstart(dma->dirty_pgsize, region->info.iova.iov_base, sg->offset);
*end = _get_pgend(dma->dirty_pgsize, sg->length, *start);
}
static void
_dma_mark_dirty(const dma_controller_t *dma, const dma_memory_region_t *region,
dma_sg_t *sg)
{
size_t i, start, end;
assert(dma != NULL);
assert(region != NULL);
assert(sg != NULL);
assert(region->dirty_bitmap != NULL);
_dma_bitmap_get_pgrange(dma, region, sg, &start, &end);
for (i = start; i <= end; i++) {
region->dirty_bitmap[i / CHAR_BIT] |= 1 << (i % CHAR_BIT);
}
}
static inline int
dma_init_sg(const dma_controller_t *dma, dma_sg_t *sg, vfu_dma_addr_t dma_addr,
uint32_t len, int prot, int region_index)
{
const dma_memory_region_t *const region = &dma->regions[region_index];
if ((prot & PROT_WRITE) && !(region->info.prot & PROT_WRITE)) {
errno = EACCES;
return -1;
}
sg->dma_addr = region->info.iova.iov_base;
sg->region = region_index;
sg->offset = dma_addr - region->info.iova.iov_base;
sg->length = len;
if (_dma_should_mark_dirty(dma, prot)) {
_dma_mark_dirty(dma, region, sg);
}
sg->mappable = (region->info.vaddr != NULL);
return 0;
}
/* Takes a linear dma address span and returns a sg list suitable for DMA.
* A single linear dma address span may need to be split into multiple
* scatter gather regions due to limitations of how memory can be mapped.
*
* Returns:
* - On success, number of scatter gather entries created.
* - On failure:
* -1 if
* - the DMA address span is invalid
* - protection violation (errno=EACCES)
* (-x - 1) if @max_sg is too small, where x is the number of sg entries
* necessary to complete this request.
*/
static inline int
dma_addr_to_sg(const dma_controller_t *dma,
vfu_dma_addr_t dma_addr, size_t len,
dma_sg_t *sg, int max_sg, int prot)
{
static __thread int region_hint;
int cnt, ret;
const dma_memory_region_t *const region = &dma->regions[region_hint];
const void *region_end = iov_end(®ion->info.iova);
// Fast path: single region.
if (likely(max_sg > 0 && len > 0 &&
dma_addr >= region->info.iova.iov_base &&
dma_addr + len <= region_end &&
region_hint < dma->nregions)) {
ret = dma_init_sg(dma, sg, dma_addr, len, prot, region_hint);
if (ret < 0) {
return ret;
}
return 1;
}
// Slow path: search through regions.
cnt = _dma_addr_sg_split(dma, dma_addr, len, sg, max_sg, prot);
if (likely(cnt > 0)) {
region_hint = sg->region;
}
return cnt;
}
static inline int
dma_map_sg(dma_controller_t *dma, const dma_sg_t *sg, struct iovec *iov,
int cnt)
{
dma_memory_region_t *region;
int i;
assert(dma != NULL);
assert(sg != NULL);
assert(iov != NULL);
for (i = 0; i < cnt; i++) {
if (sg[i].region >= dma->nregions) {
return -EINVAL;
}
region = &dma->regions[sg[i].region];
if (region->info.vaddr == NULL) {
return -EFAULT;
}
vfu_log(dma->vfu_ctx, LOG_DEBUG, "map %p-%p\n",
sg->dma_addr + sg->offset,
sg->dma_addr + sg->offset + sg->length);
iov[i].iov_base = region->info.vaddr + sg[i].offset;
iov[i].iov_len = sg[i].length;
region->refcnt++;
}
return 0;
}
static inline void
dma_unmap_sg(dma_controller_t *dma, const dma_sg_t *sg,
UNUSED struct iovec *iov, int cnt)
{
int i;
for (i = 0; i < cnt; i++) {
dma_memory_region_t *r;
/*
* FIXME this double loop will be removed if we replace the array with
* tfind(3)
*/
for (r = dma->regions;
r < dma->regions + dma->nregions &&
r->info.iova.iov_base != sg[i].dma_addr;
r++);
if (r > dma->regions + dma->nregions) {
/* bad region */
continue;
}
vfu_log(dma->vfu_ctx, LOG_DEBUG, "unmap %p-%p\n",
sg[i].dma_addr + sg[i].offset,
sg[i].dma_addr + sg[i].offset + sg[i].length);
r->refcnt--;
}
return;
}
int
dma_controller_dirty_page_logging_start(dma_controller_t *dma, size_t pgsize);
int
dma_controller_dirty_page_logging_stop(dma_controller_t *dma);
int
dma_controller_dirty_page_get(dma_controller_t *dma, vfu_dma_addr_t addr,
int len, size_t pgsize, size_t size, char **data);
#endif /* LIB_VFIO_USER_DMA_H */
/* ex: set tabstop=4 shiftwidth=4 softtabstop=4 expandtab: */
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