[RFC PATCH 1/5] drm/ttm: Add a generic TTM memcpy move for page-based iomem
Christian König
christian.koenig at amd.com
Fri May 21 08:08:30 UTC 2021
Am 20.05.21 um 17:09 schrieb Thomas Hellström:
> The internal ttm_bo_util memcpy uses ioremap functionality, and while it
> probably might be possible to use it for copying in- and out of
> sglist represented io memory, using io_mem_reserve() / io_mem_free()
> callbacks, that would cause problems with fault().
> Instead, implement a method mapping page-by-page using kmap_local()
> semantics. As an additional benefit we then avoid the occasional global
> TLB flushes of ioremap() and consuming ioremap space, elimination of a
> critical point of failure and with a slight change of semantics we could
> also push the memcpy out async for testing and async driver development
> purposes.
>
> A special linear iomem iterator is introduced internally to mimic the
> old ioremap behaviour for code-paths that can't immediately be ported
> over. This adds to the code size and should be considered a temporary
> solution.
>
> Looking at the code we have a lot of checks for iomap tagged pointers.
> Ideally we should extend the core memremap functions to also accept
> uncached memory and kmap_local functionality. Then we could strip a
> lot of code.
>
> Cc: Christian König <christian.koenig at amd.com>
> Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
> ---
> drivers/gpu/drm/ttm/ttm_bo_util.c | 468 ++++++++++++++++++++----------
> include/drm/ttm/ttm_bo_driver.h | 94 ++++++
> 2 files changed, 407 insertions(+), 155 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
> index ae8b61460724..bad9b16e96ba 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo_util.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
> @@ -35,11 +35,13 @@
> #include <linux/dma-buf-map.h>
> #include <linux/io.h>
> #include <linux/highmem.h>
> +#include <linux/io-mapping.h>
> #include <linux/wait.h>
> #include <linux/slab.h>
> #include <linux/vmalloc.h>
> #include <linux/module.h>
> #include <linux/dma-resv.h>
> +#include <linux/scatterlist.h>
>
> struct ttm_transfer_obj {
> struct ttm_buffer_object base;
> @@ -72,190 +74,366 @@ void ttm_mem_io_free(struct ttm_device *bdev,
> mem->bus.addr = NULL;
> }
>
> -static int ttm_resource_ioremap(struct ttm_device *bdev,
> - struct ttm_resource *mem,
> - void **virtual)
> +static pgprot_t ttm_prot_from_caching(enum ttm_caching caching, pgprot_t tmp)
Could you move this to ttm_module.c, creating a separate ttm_caching.c
sounds overkill but it is rather independent from the BO object.
> {
> - int ret;
> - void *addr;
> + /* Cached mappings need no adjustment */
> + if (caching == ttm_cached)
> + return tmp;
>
> - *virtual = NULL;
> - ret = ttm_mem_io_reserve(bdev, mem);
> - if (ret || !mem->bus.is_iomem)
> - return ret;
> +#if defined(__i386__) || defined(__x86_64__)
> + if (caching == ttm_write_combined)
> + tmp = pgprot_writecombine(tmp);
> + else if (boot_cpu_data.x86 > 3)
> + tmp = pgprot_noncached(tmp);
> +#endif
> +#if defined(__ia64__) || defined(__arm__) || defined(__aarch64__) || \
> + defined(__powerpc__) || defined(__mips__)
> + if (caching == ttm_write_combined)
> + tmp = pgprot_writecombine(tmp);
> + else
> + tmp = pgprot_noncached(tmp);
> +#endif
> +#if defined(__sparc__)
> + tmp = pgprot_noncached(tmp);
> +#endif
> + return tmp;
> +}
>
> - if (mem->bus.addr) {
> - addr = mem->bus.addr;
> - } else {
> - size_t bus_size = (size_t)mem->num_pages << PAGE_SHIFT;
> +static void ttm_kmap_iter_tt_kmap_local(struct ttm_kmap_iter *iter,
> + struct dma_buf_map *dmap,
> + pgoff_t i)
I really like the idea of the iterator, but I think we should move the
code for iterating over TT and iterating over resource object to
ttm_tt.c and ttm_resource.c respectively.
> +{
> + struct ttm_kmap_iter_tt *iter_tt =
> + container_of(iter, typeof(*iter_tt), base);
>
> - if (mem->bus.caching == ttm_write_combined)
> - addr = ioremap_wc(mem->bus.offset, bus_size);
> -#ifdef CONFIG_X86
> - else if (mem->bus.caching == ttm_cached)
> - addr = ioremap_cache(mem->bus.offset, bus_size);
> -#endif
> - else
> - addr = ioremap(mem->bus.offset, bus_size);
> - if (!addr) {
> - ttm_mem_io_free(bdev, mem);
> - return -ENOMEM;
> - }
> + dma_buf_map_set_vaddr(dmap, kmap_local_page_prot(iter_tt->tt->pages[i],
> + iter_tt->prot));
> +}
> +
> +static void ttm_kmap_iter_iomap_kmap_local(struct ttm_kmap_iter *iter,
> + struct dma_buf_map *dmap,
> + pgoff_t i)
> +{
> + struct ttm_kmap_iter_iomap *iter_io =
> + container_of(iter, typeof(*iter_io), base);
> + void __iomem *addr;
> +
> +retry:
> + while (i >= iter_io->cache.end) {
> + iter_io->cache.sg = iter_io->cache.sg ?
> + sg_next(iter_io->cache.sg) : iter_io->st->sgl;
> + iter_io->cache.i = iter_io->cache.end;
> + iter_io->cache.end += sg_dma_len(iter_io->cache.sg) >>
> + PAGE_SHIFT;
> + iter_io->cache.offs = sg_dma_address(iter_io->cache.sg) -
> + iter_io->start;
> }
> - *virtual = addr;
> - return 0;
> +
> + if (i < iter_io->cache.i) {
> + iter_io->cache.end = 0;
> + iter_io->cache.sg = NULL;
> + goto retry;
> + }
> +
> + addr = io_mapping_map_local_wc(iter_io->iomap, iter_io->cache.offs +
> + (((resource_size_t)i - iter_io->cache.i)
> + << PAGE_SHIFT));
> + dma_buf_map_set_vaddr_iomem(dmap, addr);
> }
>
> -static void ttm_resource_iounmap(struct ttm_device *bdev,
> - struct ttm_resource *mem,
> - void *virtual)
> +static const struct ttm_kmap_iter_ops ttm_kmap_iter_tt_ops = {
> + .kmap_local = ttm_kmap_iter_tt_kmap_local,
> + .needs_unmap = true
> +};
> +
> +static const struct ttm_kmap_iter_ops ttm_kmap_iter_io_ops = {
> + .kmap_local = ttm_kmap_iter_iomap_kmap_local,
> + .needs_unmap = true
I think we should rather have an map and an unmap callback instead of
the needs_unmap flag.
Christian.
> +};
> +
> +/* If needed, make unmap functionality part of ttm_kmap_iter_ops */
> +static void kunmap_local_iter(struct ttm_kmap_iter *iter,
> + struct dma_buf_map *map)
> {
> - if (virtual && mem->bus.addr == NULL)
> - iounmap(virtual);
> - ttm_mem_io_free(bdev, mem);
> + if (!iter->ops->needs_unmap)
> + return;
> +
> + if (map->is_iomem)
> + io_mapping_unmap_local(map->vaddr_iomem);
> + else
> + kunmap_local(map->vaddr);
> }
>
> -static int ttm_copy_io_page(void *dst, void *src, unsigned long page)
> +/**
> + * ttm_move_memcpy - Helper to perform a memcpy ttm move operation.
> + * @bo: The struct ttm_buffer_object.
> + * @new_mem: The struct ttm_resource we're moving to (copy destination).
> + * @new_iter: A struct ttm_kmap_iter representing the destination resource.
> + * @old_iter: A struct ttm_kmap_iter representing the source resource.
> + *
> + * This function is intended to be able to move out async under a
> + * dma-fence if desired.
> + */
> +void ttm_move_memcpy(struct ttm_buffer_object *bo,
> + struct ttm_resource *new_mem,
> + struct ttm_kmap_iter *new_iter,
> + struct ttm_kmap_iter *old_iter)
> {
> - uint32_t *dstP =
> - (uint32_t *) ((unsigned long)dst + (page << PAGE_SHIFT));
> - uint32_t *srcP =
> - (uint32_t *) ((unsigned long)src + (page << PAGE_SHIFT));
> -
> - int i;
> - for (i = 0; i < PAGE_SIZE / sizeof(uint32_t); ++i)
> - iowrite32(ioread32(srcP++), dstP++);
> - return 0;
> + struct ttm_device *bdev = bo->bdev;
> + struct ttm_resource_manager *man = ttm_manager_type(bdev, new_mem->mem_type);
> + struct ttm_tt *ttm = bo->ttm;
> + struct ttm_resource *old_mem = &bo->mem;
> + struct ttm_resource_manager *old_man = ttm_manager_type(bdev, old_mem->mem_type);
> + struct dma_buf_map old_map, new_map;
> + pgoff_t i;
> +
> + /* Single TTM move. NOP */
> + if (old_man->use_tt && man->use_tt)
> + return;
> +
> + /* Don't move nonexistent data. Clear destination instead. */
> + if (old_man->use_tt && !man->use_tt &&
> + (!ttm || !ttm_tt_is_populated(ttm))) {
> + if (ttm && !(ttm->page_flags & TTM_PAGE_FLAG_ZERO_ALLOC))
> + return;
> +
> + for (i = 0; i < new_mem->num_pages; ++i) {
> + new_iter->ops->kmap_local(new_iter, &new_map, i);
> + if (new_map.is_iomem)
> + memset_io(new_map.vaddr_iomem, 0, PAGE_SIZE);
> + else
> + memset(new_map.vaddr, 0, PAGE_SIZE);
> + kunmap_local_iter(new_iter, &new_map);
> + }
> + return;
> + }
> +
> + for (i = 0; i < new_mem->num_pages; ++i) {
> + new_iter->ops->kmap_local(new_iter, &new_map, i);
> + old_iter->ops->kmap_local(old_iter, &old_map, i);
> +
> + if (!old_map.is_iomem && !new_map.is_iomem) {
> + memcpy(new_map.vaddr, old_map.vaddr, PAGE_SIZE);
> + } else if (!old_map.is_iomem) {
> + dma_buf_map_memcpy_to(&new_map, old_map.vaddr,
> + PAGE_SIZE);
> + } else if (!new_map.is_iomem) {
> + memcpy_fromio(new_map.vaddr, old_map.vaddr_iomem,
> + PAGE_SIZE);
> + } else {
> + int j;
> + u32 __iomem *src = old_map.vaddr_iomem;
> + u32 __iomem *dst = new_map.vaddr_iomem;
> +
> + for (j = 0; j < (PAGE_SIZE >> 2); ++j)
> + iowrite32(ioread32(src++), dst++);
> + }
> + kunmap_local_iter(old_iter, &old_map);
> + kunmap_local_iter(new_iter, &new_map);
> + }
> }
> +EXPORT_SYMBOL(ttm_move_memcpy);
>
> -static int ttm_copy_io_ttm_page(struct ttm_tt *ttm, void *src,
> - unsigned long page,
> - pgprot_t prot)
> +/**
> + * ttm_kmap_iter_iomap_init - Initialize a struct ttm_kmap_iter_iomap
> + * @iter_io: The struct ttm_kmap_iter_iomap to initialize.
> + * @iomap: The struct io_mapping representing the underlying linear io_memory.
> + * @st: sg_table into @iomap, representing the memory of the struct
> + * ttm_resource.
> + * @start: Offset that needs to be subtracted from @st to make
> + * sg_dma_address(st->sgl) - @start == 0 for @iomap start.
> + *
> + * Return: Pointer to the embedded struct ttm_kmap_iter.
> + */
> +struct ttm_kmap_iter *
> +ttm_kmap_iter_iomap_init(struct ttm_kmap_iter_iomap *iter_io,
> + struct io_mapping *iomap,
> + struct sg_table *st,
> + resource_size_t start)
> {
> - struct page *d = ttm->pages[page];
> - void *dst;
> + iter_io->base.ops = &ttm_kmap_iter_io_ops;
> + iter_io->iomap = iomap;
> + iter_io->st = st;
> + iter_io->start = start;
> + memset(&iter_io->cache, 0, sizeof(iter_io->cache));
>
> - if (!d)
> - return -ENOMEM;
> + return &iter_io->base;
> +}
> +EXPORT_SYMBOL(ttm_kmap_iter_iomap_init);
>
> - src = (void *)((unsigned long)src + (page << PAGE_SHIFT));
> - dst = kmap_atomic_prot(d, prot);
> - if (!dst)
> - return -ENOMEM;
> +/**
> + * ttm_kmap_iter_tt_init - Initialize a struct ttm_kmap_iter_tt
> + * @iter_tt: The struct ttm_kmap_iter_tt to initialize.
> + * @tt: Struct ttm_tt holding page pointers of the struct ttm_resource.
> + *
> + * Return: Pointer to the embedded struct ttm_kmap_iter.
> + */
> +struct ttm_kmap_iter *
> +ttm_kmap_iter_tt_init(struct ttm_kmap_iter_tt *iter_tt,
> + struct ttm_tt *tt)
> +{
> + iter_tt->base.ops = &ttm_kmap_iter_tt_ops;
> + iter_tt->tt = tt;
> + iter_tt->prot = ttm_prot_from_caching(tt->caching, PAGE_KERNEL);
>
> - memcpy_fromio(dst, src, PAGE_SIZE);
> + return &iter_tt->base;
> +}
> +EXPORT_SYMBOL(ttm_kmap_iter_tt_init);
>
> - kunmap_atomic(dst);
> +/**
> + * DOC: Linear io iterator
> + *
> + * This code should die in the not too near future. Best would be if we could
> + * make io-mapping use memremap for all io memory, and have memremap
> + * implement a kmap_local functionality. We could then strip a huge amount of
> + * code. These linear io iterators are implemented to mimic old functionality,
> + * and they don't use kmap_local semantics at all internally. Rather ioremap or
> + * friends, and at least on 32-bit they add global TLB flushes and points
> + * of failure.
> + */
>
> - return 0;
> +/**
> + * struct ttm_kmap_iter_linear_io - Iterator specialization for linear io
> + * @base: The base iterator
> + * @dmap: Points to the starting address of the region
> + * @needs_unmap: Whether we need to unmap on fini
> + */
> +struct ttm_kmap_iter_linear_io {
> + struct ttm_kmap_iter base;
> + struct dma_buf_map dmap;
> + bool needs_unmap;
> +};
> +
> +static void ttm_kmap_iter_linear_io_kmap_local(struct ttm_kmap_iter *iter,
> + struct dma_buf_map *dmap,
> + pgoff_t i)
> +{
> + struct ttm_kmap_iter_linear_io *iter_io =
> + container_of(iter, typeof(*iter_io), base);
> +
> + *dmap = iter_io->dmap;
> + dma_buf_map_incr(dmap, i * PAGE_SIZE);
> }
>
> -static int ttm_copy_ttm_io_page(struct ttm_tt *ttm, void *dst,
> - unsigned long page,
> - pgprot_t prot)
> +static const struct ttm_kmap_iter_ops ttm_kmap_iter_linear_io_ops = {
> + .kmap_local = ttm_kmap_iter_linear_io_kmap_local
> +};
> +
> +static struct ttm_kmap_iter *
> +ttm_kmap_iter_linear_io_init(struct ttm_kmap_iter_linear_io *iter_io,
> + struct ttm_device *bdev,
> + struct ttm_resource *mem)
> {
> - struct page *s = ttm->pages[page];
> - void *src;
> + int ret;
>
> - if (!s)
> - return -ENOMEM;
> + ret = ttm_mem_io_reserve(bdev, mem);
> + if (ret)
> + goto out_err;
> + if (!mem->bus.is_iomem) {
> + ret = -EINVAL;
> + goto out_io_free;
> + }
>
> - dst = (void *)((unsigned long)dst + (page << PAGE_SHIFT));
> - src = kmap_atomic_prot(s, prot);
> - if (!src)
> - return -ENOMEM;
> + if (mem->bus.addr) {
> + dma_buf_map_set_vaddr(&iter_io->dmap, mem->bus.addr);
> + iter_io->needs_unmap = false;
> + } else {
> + size_t bus_size = (size_t)mem->num_pages << PAGE_SHIFT;
>
> - memcpy_toio(dst, src, PAGE_SIZE);
> + iter_io->needs_unmap = true;
> + if (mem->bus.caching == ttm_write_combined)
> + dma_buf_map_set_vaddr_iomem(&iter_io->dmap,
> + ioremap_wc(mem->bus.offset,
> + bus_size));
> + else if (mem->bus.caching == ttm_cached)
> + dma_buf_map_set_vaddr(&iter_io->dmap,
> + memremap(mem->bus.offset, bus_size,
> + MEMREMAP_WB));
> + else
> + dma_buf_map_set_vaddr_iomem(&iter_io->dmap,
> + ioremap(mem->bus.offset,
> + bus_size));
> + if (dma_buf_map_is_null(&iter_io->dmap)) {
> + ret = -ENOMEM;
> + goto out_io_free;
> + }
> + }
>
> - kunmap_atomic(src);
> + iter_io->base.ops = &ttm_kmap_iter_linear_io_ops;
> + return &iter_io->base;
>
> - return 0;
> +out_io_free:
> + ttm_mem_io_free(bdev, mem);
> +out_err:
> + return ERR_PTR(ret);
> +}
> +
> +static void
> +ttm_kmap_iter_linear_io_fini(struct ttm_kmap_iter_linear_io *iter_io,
> + struct ttm_device *bdev,
> + struct ttm_resource *mem)
> +{
> + if (iter_io->needs_unmap && dma_buf_map_is_set(&iter_io->dmap)) {
> + if (iter_io->dmap.is_iomem)
> + iounmap(iter_io->dmap.vaddr_iomem);
> + else
> + memunmap(iter_io->dmap.vaddr);
> + }
> +
> + ttm_mem_io_free(bdev, mem);
> }
>
> +static int ttm_bo_wait_free_node(struct ttm_buffer_object *bo,
> + bool dst_use_tt);
> +
> int ttm_bo_move_memcpy(struct ttm_buffer_object *bo,
> struct ttm_operation_ctx *ctx,
> struct ttm_resource *new_mem)
> {
> struct ttm_device *bdev = bo->bdev;
> struct ttm_resource_manager *man = ttm_manager_type(bdev, new_mem->mem_type);
> + struct ttm_resource_manager *new_man =
> + ttm_manager_type(bo->bdev, new_mem->mem_type);
> struct ttm_tt *ttm = bo->ttm;
> struct ttm_resource *old_mem = &bo->mem;
> struct ttm_resource old_copy = *old_mem;
> - void *old_iomap;
> - void *new_iomap;
> + union {
> + struct ttm_kmap_iter_tt tt;
> + struct ttm_kmap_iter_linear_io io;
> + } _new_iter, _old_iter;
> + struct ttm_kmap_iter *new_iter, *old_iter;
> int ret;
> - unsigned long i;
> -
> - ret = ttm_bo_wait_ctx(bo, ctx);
> - if (ret)
> - return ret;
> -
> - ret = ttm_resource_ioremap(bdev, old_mem, &old_iomap);
> - if (ret)
> - return ret;
> - ret = ttm_resource_ioremap(bdev, new_mem, &new_iomap);
> - if (ret)
> - goto out;
> -
> - /*
> - * Single TTM move. NOP.
> - */
> - if (old_iomap == NULL && new_iomap == NULL)
> - goto out2;
>
> - /*
> - * Don't move nonexistent data. Clear destination instead.
> - */
> - if (old_iomap == NULL &&
> - (ttm == NULL || (!ttm_tt_is_populated(ttm) &&
> - !(ttm->page_flags & TTM_PAGE_FLAG_SWAPPED)))) {
> - memset_io(new_iomap, 0, new_mem->num_pages*PAGE_SIZE);
> - goto out2;
> - }
> -
> - /*
> - * TTM might be null for moves within the same region.
> - */
> if (ttm) {
> ret = ttm_tt_populate(bdev, ttm, ctx);
> if (ret)
> - goto out1;
> + return ret;
> }
>
> - for (i = 0; i < new_mem->num_pages; ++i) {
> - if (old_iomap == NULL) {
> - pgprot_t prot = ttm_io_prot(bo, old_mem, PAGE_KERNEL);
> - ret = ttm_copy_ttm_io_page(ttm, new_iomap, i,
> - prot);
> - } else if (new_iomap == NULL) {
> - pgprot_t prot = ttm_io_prot(bo, new_mem, PAGE_KERNEL);
> - ret = ttm_copy_io_ttm_page(ttm, old_iomap, i,
> - prot);
> - } else {
> - ret = ttm_copy_io_page(new_iomap, old_iomap, i);
> - }
> - if (ret)
> - goto out1;
> + new_iter = new_man->use_tt ?
> + ttm_kmap_iter_tt_init(&_new_iter.tt, bo->ttm) :
> + ttm_kmap_iter_linear_io_init(&_new_iter.io, bdev, new_mem);
> + if (IS_ERR(new_iter))
> + return PTR_ERR(new_iter);
> +
> + old_iter = man->use_tt ?
> + ttm_kmap_iter_tt_init(&_old_iter.tt, bo->ttm) :
> + ttm_kmap_iter_linear_io_init(&_old_iter.io, bdev, old_mem);
> + if (IS_ERR(old_iter)) {
> + ret = PTR_ERR(old_iter);
> + goto out_old_iter;
> }
> - mb();
> -out2:
> - old_copy = *old_mem;
>
> - ttm_bo_assign_mem(bo, new_mem);
> + ttm_move_memcpy(bo, new_mem, new_iter, old_iter);
> + old_copy = *old_mem;
> + ret = ttm_bo_wait_free_node(bo, new_man->use_tt);
>
> if (!man->use_tt)
> - ttm_bo_tt_destroy(bo);
> + ttm_kmap_iter_linear_io_fini(&_old_iter.io, bdev, &old_copy);
> +out_old_iter:
> + if (!new_man->use_tt)
> + ttm_kmap_iter_linear_io_fini(&_new_iter.io, bdev, new_mem);
>
> -out1:
> - ttm_resource_iounmap(bdev, old_mem, new_iomap);
> -out:
> - ttm_resource_iounmap(bdev, &old_copy, old_iomap);
> -
> - /*
> - * On error, keep the mm node!
> - */
> - if (!ret)
> - ttm_resource_free(bo, &old_copy);
> return ret;
> }
> EXPORT_SYMBOL(ttm_bo_move_memcpy);
> @@ -336,27 +514,7 @@ pgprot_t ttm_io_prot(struct ttm_buffer_object *bo, struct ttm_resource *res,
> man = ttm_manager_type(bo->bdev, res->mem_type);
> caching = man->use_tt ? bo->ttm->caching : res->bus.caching;
>
> - /* Cached mappings need no adjustment */
> - if (caching == ttm_cached)
> - return tmp;
> -
> -#if defined(__i386__) || defined(__x86_64__)
> - if (caching == ttm_write_combined)
> - tmp = pgprot_writecombine(tmp);
> - else if (boot_cpu_data.x86 > 3)
> - tmp = pgprot_noncached(tmp);
> -#endif
> -#if defined(__ia64__) || defined(__arm__) || defined(__aarch64__) || \
> - defined(__powerpc__) || defined(__mips__)
> - if (caching == ttm_write_combined)
> - tmp = pgprot_writecombine(tmp);
> - else
> - tmp = pgprot_noncached(tmp);
> -#endif
> -#if defined(__sparc__)
> - tmp = pgprot_noncached(tmp);
> -#endif
> - return tmp;
> + return ttm_prot_from_caching(caching, tmp);
> }
> EXPORT_SYMBOL(ttm_io_prot);
>
> diff --git a/include/drm/ttm/ttm_bo_driver.h b/include/drm/ttm/ttm_bo_driver.h
> index dbccac957f8f..30f1dce987b2 100644
> --- a/include/drm/ttm/ttm_bo_driver.h
> +++ b/include/drm/ttm/ttm_bo_driver.h
> @@ -332,4 +332,98 @@ int ttm_range_man_init(struct ttm_device *bdev,
> int ttm_range_man_fini(struct ttm_device *bdev,
> unsigned type);
>
> +struct dma_buf_map;
> +struct io_mapping;
> +struct sg_table;
> +struct scatterlist;
> +struct ttm_kmap_iter;
> +
> +/**
> + * struct ttm_kmap_iter_ops - Ops structure for a struct
> + * ttm_kmap_iter.
> + * @needs_unmap - Whether a kunmap_local is needed to balance @kmap_local.
> + */
> +struct ttm_kmap_iter_ops {
> + /**
> + * kmap_local - Map a PAGE_SIZE part of the resource using
> + * kmap_local semantics.
> + * @res_kmap: Pointer to the struct ttm_kmap_iter representing
> + * the resource.
> + * @dmap: The struct dma_buf_map holding the virtual address after
> + * the operation.
> + * @i: The location within the resource to map. PAGE_SIZE granularity.
> + */
> + void (*kmap_local)(struct ttm_kmap_iter *res_kmap,
> + struct dma_buf_map *dmap, pgoff_t i);
> + bool needs_unmap;
> +};
> +
> +/**
> + * struct ttm_kmap_iter - Iterator for kmap_local type operations on a
> + * resource.
> + * @ops: Pointer to the operations struct.
> + *
> + * This struct is intended to be embedded in a resource-specific specialization
> + * implementing operations for the resource.
> + *
> + * Nothing stops us from extending the operations to vmap, vmap_pfn etc,
> + * replacing some or parts of the ttm_bo_util. cpu-map functionality.
> + */
> +struct ttm_kmap_iter {
> + const struct ttm_kmap_iter_ops *ops;
> +};
> +
> +/**
> + * struct ttm_kmap_iter_tt - Specialization for a tt (page) backed struct
> + * ttm_resource.
> + * @base: Embedded struct ttm_kmap_iter providing the usage interface
> + * @tt: Cached struct ttm_tt.
> + */
> +struct ttm_kmap_iter_tt {
> + struct ttm_kmap_iter base;
> + struct ttm_tt *tt;
> + pgprot_t prot;
> +};
> +
> +/**
> + * struct ttm_kmap_iter_iomap - Specialization for a struct io_mapping +
> + * struct sg_table backed struct ttm_resource.
> + * @base: Embedded struct ttm_kmap_iter providing the usage interface.
> + * @iomap: struct io_mapping representing the underlying linear io_memory.
> + * @st: sg_table into @iomap, representing the memory of the struct ttm_resource.
> + * @start: Offset that needs to be subtracted from @st to make
> + * sg_dma_address(st->sgl) - @start == 0 for @iomap start.
> + * @cache: Scatterlist traversal cache for fast lookups.
> + * @cache.sg: Pointer to the currently cached scatterlist segment.
> + * @cache.i: First index of @sg. PAGE_SIZE granularity.
> + * @cache.end: Last index + 1 of @sg. PAGE_SIZE granularity.
> + * @cache.offs: First offset into @iomap of @sg. PAGE_SIZE granularity.
> + */
> +struct ttm_kmap_iter_iomap {
> + struct ttm_kmap_iter base;
> + struct io_mapping *iomap;
> + struct sg_table *st;
> + resource_size_t start;
> + struct {
> + struct scatterlist *sg;
> + pgoff_t i;
> + pgoff_t end;
> + pgoff_t offs;
> + } cache;
> +};
> +
> +void ttm_move_memcpy(struct ttm_buffer_object *bo,
> + struct ttm_resource *new_mem,
> + struct ttm_kmap_iter *new_iter,
> + struct ttm_kmap_iter *old_iter);
> +
> +struct ttm_kmap_iter *
> +ttm_kmap_iter_tt_init(struct ttm_kmap_iter_tt *iter_tt,
> + struct ttm_tt *tt);
> +
> +struct ttm_kmap_iter *
> +ttm_kmap_iter_iomap_init(struct ttm_kmap_iter_iomap *iter_io,
> + struct io_mapping *iomap,
> + struct sg_table *st,
> + resource_size_t start);
> #endif
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