[Intel-gfx] [PATCH v3 06/12] drm/ttm: Add a generic TTM memcpy move for page-based iomem
Thomas Hellström
thomas.hellstrom at linux.intel.com
Tue May 25 10:07:55 UTC 2021
On Tue, 2021-05-25 at 10:58 +0100, Matthew Auld wrote:
> On Tue, 25 May 2021 at 10:32, Thomas Hellström
> <thomas.hellstrom at linux.intel.com> wrote:
> >
> >
> > On 5/25/21 11:18 AM, Matthew Auld wrote:
> > > On Fri, 21 May 2021 at 16:33, Thomas Hellström
> > > <thomas.hellstrom at linux.intel.com> wrote:
> > > > 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>
> > > > ---
> > > > v3:
> > > > - Split up in various TTM files and addressed review comments
> > > > by
> > > > Christian König. Tested and fixed legacy iomap memcpy path
> > > > on i915.
> > > > ---
> > > > drivers/gpu/drm/ttm/ttm_bo_util.c | 278 ++++++++++----------
> > > > ---------
> > > > drivers/gpu/drm/ttm/ttm_module.c | 35 ++++
> > > > drivers/gpu/drm/ttm/ttm_resource.c | 166 +++++++++++++++++
> > > > drivers/gpu/drm/ttm/ttm_tt.c | 42 +++++
> > > > include/drm/ttm/ttm_bo_driver.h | 28 +++
> > > > include/drm/ttm/ttm_caching.h | 2 +
> > > > include/drm/ttm/ttm_kmap_iter.h | 61 +++++++
> > > > include/drm/ttm/ttm_resource.h | 61 +++++++
> > > > include/drm/ttm/ttm_tt.h | 16 ++
> > > > 9 files changed, 508 insertions(+), 181 deletions(-)
> > > > create mode 100644 include/drm/ttm/ttm_kmap_iter.h
> > > >
> > > > diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c
> > > > b/drivers/gpu/drm/ttm/ttm_bo_util.c
> > > > index ae8b61460724..912cbe8e60a2 100644
> > > > --- a/drivers/gpu/drm/ttm/ttm_bo_util.c
> > > > +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
> > > > @@ -72,190 +72,126 @@ 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)
> > > > +/**
> > > > + * 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.
> > > > + * @src_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 *dst_mem,
> > > > + struct ttm_kmap_iter *dst_iter,
> > > > + struct ttm_kmap_iter *src_iter)
> > > > {
> > > > - int ret;
> > > > - void *addr;
> > > > -
> > > > - *virtual = NULL;
> > > > - ret = ttm_mem_io_reserve(bdev, mem);
> > > > - if (ret || !mem->bus.is_iomem)
> > > > - return ret;
> > > > + const struct ttm_kmap_iter_ops *dst_ops = dst_iter-
> > > > >ops;
> > > > + const struct ttm_kmap_iter_ops *src_ops = src_iter-
> > > > >ops;
> > > > + struct ttm_tt *ttm = bo->ttm;
> > > > + struct dma_buf_map src_map, dst_map;
> > > > + pgoff_t i;
> > > >
> > > > - if (mem->bus.addr) {
> > > > - addr = mem->bus.addr;
> > > > - } else {
> > > > - size_t bus_size = (size_t)mem->num_pages <<
> > > > PAGE_SHIFT;
> > > > + /* Single TTM move. NOP */
> > > > + if (dst_ops->maps_tt && src_ops->maps_tt)
> > > > + return;
> > > >
> > > > - 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;
> > > > + /* Don't move nonexistent data. Clear destination
> > > > instead. */
> > > > + if (src_ops->maps_tt && (!ttm ||
> > > > !ttm_tt_is_populated(ttm))) {
> > > > + if (ttm && !(ttm->page_flags &
> > > > TTM_PAGE_FLAG_ZERO_ALLOC))
> > > > + return;
> > > > +
> > > > + for (i = 0; i < dst_mem->num_pages; ++i) {
> > > > + dst_ops->map_local(dst_iter, &dst_map,
> > > > i);
> > > > + if (dst_map.is_iomem)
> > > > + memset_io(dst_map.vaddr_iomem,
> > > > 0, PAGE_SIZE);
> > > > + else
> > > > + memset(dst_map.vaddr, 0,
> > > > PAGE_SIZE);
> > > > + if (dst_ops->unmap_local)
> > > > + dst_ops->unmap_local(dst_iter,
> > > > &dst_map);
> > > > }
> > > > + return;
> > > > }
> > > > - *virtual = addr;
> > > > - return 0;
> > > > -}
> > > > -
> > > > -static void ttm_resource_iounmap(struct ttm_device *bdev,
> > > > - struct ttm_resource *mem,
> > > > - void *virtual)
> > > > -{
> > > > - if (virtual && mem->bus.addr == NULL)
> > > > - iounmap(virtual);
> > > > - ttm_mem_io_free(bdev, mem);
> > > > -}
> > > > -
> > > > -static int ttm_copy_io_page(void *dst, void *src, unsigned
> > > > long page)
> > > > -{
> > > > - 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;
> > > > -}
> > > > -
> > > > -static int ttm_copy_io_ttm_page(struct ttm_tt *ttm, void *src,
> > > > - unsigned long page,
> > > > - pgprot_t prot)
> > > > -{
> > > > - struct page *d = ttm->pages[page];
> > > > - void *dst;
> > > > -
> > > > - if (!d)
> > > > - return -ENOMEM;
> > > > -
> > > > - src = (void *)((unsigned long)src + (page <<
> > > > PAGE_SHIFT));
> > > > - dst = kmap_atomic_prot(d, prot);
> > > > - if (!dst)
> > > > - return -ENOMEM;
> > > > -
> > > > - memcpy_fromio(dst, src, PAGE_SIZE);
> > > > -
> > > > - kunmap_atomic(dst);
> > > > -
> > > > - return 0;
> > > > -}
> > > > -
> > > > -static int ttm_copy_ttm_io_page(struct ttm_tt *ttm, void *dst,
> > > > - unsigned long page,
> > > > - pgprot_t prot)
> > > > -{
> > > > - struct page *s = ttm->pages[page];
> > > > - void *src;
> > > > -
> > > > - if (!s)
> > > > - return -ENOMEM;
> > > > -
> > > > - dst = (void *)((unsigned long)dst + (page <<
> > > > PAGE_SHIFT));
> > > > - src = kmap_atomic_prot(s, prot);
> > > > - if (!src)
> > > > - return -ENOMEM;
> > > >
> > > > - memcpy_toio(dst, src, PAGE_SIZE);
> > > > -
> > > > - kunmap_atomic(src);
> > > > + for (i = 0; i < dst_mem->num_pages; ++i) {
> > > > + dst_ops->map_local(dst_iter, &dst_map, i);
> > > > + src_ops->map_local(src_iter, &src_map, i);
> > > > +
> > > > + if (!src_map.is_iomem && !dst_map.is_iomem) {
> > > > + memcpy(dst_map.vaddr, src_map.vaddr,
> > > > PAGE_SIZE);
> > > > + } else if (!src_map.is_iomem) {
> > > > + dma_buf_map_memcpy_to(&dst_map,
> > > > src_map.vaddr,
> > > > + PAGE_SIZE);
> > > > + } else if (!dst_map.is_iomem) {
> > > > + memcpy_fromio(dst_map.vaddr,
> > > > src_map.vaddr_iomem,
> > > > + PAGE_SIZE);
> > > > + } else {
> > > > + int j;
> > > > + u32 __iomem *src = src_map.vaddr_iomem;
> > > > + u32 __iomem *dst = dst_map.vaddr_iomem;
> > > >
> > > > - return 0;
> > > > + for (j = 0; j < (PAGE_SIZE >> 2); ++j)
> > > IMO PAGE_SIZE / sizeof(u32) is easier to understand.
> >
> > OK, will fix.
> >
> >
> > >
> > > > + iowrite32(ioread32(src++),
> > > > dst++);
> > > > + }
> > > > + if (src_ops->unmap_local)
> > > > + src_ops->unmap_local(src_iter,
> > > > &src_map);
> > > > + if (dst_ops->unmap_local)
> > > > + dst_ops->unmap_local(dst_iter,
> > > > &dst_map);
> > > > + }
> > > > }
> > > > +EXPORT_SYMBOL(ttm_move_memcpy);
> > > >
> > > > int ttm_bo_move_memcpy(struct ttm_buffer_object *bo,
> > > > struct ttm_operation_ctx *ctx,
> > > > - struct ttm_resource *new_mem)
> > > > + struct ttm_resource *dst_mem)
> > > > {
> > > > struct ttm_device *bdev = bo->bdev;
> > > > - struct ttm_resource_manager *man =
> > > > ttm_manager_type(bdev, new_mem->mem_type);
> > > > + struct ttm_resource_manager *dst_man =
> > > > + ttm_manager_type(bo->bdev, dst_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;
> > > > + struct ttm_resource *src_mem = &bo->mem;
> > > > + struct ttm_resource_manager *src_man =
> > > > + ttm_manager_type(bdev, src_mem->mem_type);
> > > > + struct ttm_resource src_copy = *src_mem;
> > > > + union {
> > > > + struct ttm_kmap_iter_tt tt;
> > > > + struct ttm_kmap_iter_linear_io io;
> > > > + } _dst_iter, _src_iter;
> > > > + struct ttm_kmap_iter *dst_iter, *src_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) {
> > > > + if (ttm && ((ttm->page_flags & TTM_PAGE_FLAG_SWAPPED)
> > > > ||
> > > > + dst_man->use_tt)) {
> > > > 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;
> > > > + dst_iter = ttm_kmap_iter_linear_io_init(&_dst_iter.io,
> > > > bdev, dst_mem);
> > > > + if (PTR_ERR(dst_iter) == -EINVAL && dst_man->use_tt)
> > > > + dst_iter = ttm_kmap_iter_tt_init(&_dst_iter.tt,
> > > > bo->ttm);
> > > > + if (IS_ERR(dst_iter))
> > > > + return PTR_ERR(dst_iter);
> > > > +
> > > > + src_iter = ttm_kmap_iter_linear_io_init(&_src_iter.io,
> > > > bdev, src_mem);
> > > > + if (PTR_ERR(src_iter) == -EINVAL && src_man->use_tt)
> > > > + src_iter = ttm_kmap_iter_tt_init(&_src_iter.tt,
> > > > bo->ttm);
> > > > + if (IS_ERR(src_iter)) {
> > > > + ret = PTR_ERR(src_iter);
> > > > + goto out_src_iter;
> > > > }
> > > > - mb();
> > > > -out2:
> > > > - old_copy = *old_mem;
> > > >
> > > > - ttm_bo_assign_mem(bo, new_mem);
> > > > -
> > > > - if (!man->use_tt)
> > > > - ttm_bo_tt_destroy(bo);
> > > > + ttm_move_memcpy(bo, dst_mem, dst_iter, src_iter);
> > > > + src_copy = *src_mem;
> > > > + ttm_bo_move_sync_cleanup(bo, dst_mem);
> > > >
> > > > -out1:
> > > > - ttm_resource_iounmap(bdev, old_mem, new_iomap);
> > > > -out:
> > > > - ttm_resource_iounmap(bdev, &old_copy, old_iomap);
> > > > + if (!src_iter->ops->maps_tt)
> > > > + ttm_kmap_iter_linear_io_fini(&_src_iter.io,
> > > > bdev, &src_copy);
> > > > +out_src_iter:
> > > > + if (!dst_iter->ops->maps_tt)
> > > > + ttm_kmap_iter_linear_io_fini(&_dst_iter.io,
> > > > bdev, dst_mem);
> > > >
> > > > - /*
> > > > - * On error, keep the mm node!
> > > > - */
> > > > - if (!ret)
> > > > - ttm_resource_free(bo, &old_copy);
> > > > return ret;
> > > > }
> > > > EXPORT_SYMBOL(ttm_bo_move_memcpy);
> > > > @@ -336,27 +272,7 @@ 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/drivers/gpu/drm/ttm/ttm_module.c
> > > > b/drivers/gpu/drm/ttm/ttm_module.c
> > > > index 56b0efdba1a9..997c458f68a9 100644
> > > > --- a/drivers/gpu/drm/ttm/ttm_module.c
> > > > +++ b/drivers/gpu/drm/ttm/ttm_module.c
> > > > @@ -31,12 +31,47 @@
> > > > */
> > > > #include <linux/module.h>
> > > > #include <linux/device.h>
> > > > +#include <linux/pgtable.h>
> > > > #include <linux/sched.h>
> > > > #include <linux/debugfs.h>
> > > > #include <drm/drm_sysfs.h>
> > > > +#include <drm/ttm/ttm_caching.h>
> > > >
> > > > #include "ttm_module.h"
> > > >
> > > > +/**
> > > > + * ttm_prot_from_caching - Modify the page protection
> > > > according to the
> > > > + * ttm cacing mode
> > > > + * @caching: The ttm caching mode
> > > > + * @tmp: The original page protection
> > > > + *
> > > > + * Return: The modified page protection
> > > > + */
> > > > +pgprot_t ttm_prot_from_caching(enum ttm_caching caching,
> > > > pgprot_t tmp)
> > > > +{
> > > > + /* 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;
> > > > +}
> > > > +
> > > > struct dentry *ttm_debugfs_root;
> > > >
> > > > static int __init ttm_init(void)
> > > > diff --git a/drivers/gpu/drm/ttm/ttm_resource.c
> > > > b/drivers/gpu/drm/ttm/ttm_resource.c
> > > > index 59e2b7157e41..e05ae7e3d477 100644
> > > > --- a/drivers/gpu/drm/ttm/ttm_resource.c
> > > > +++ b/drivers/gpu/drm/ttm/ttm_resource.c
> > > > @@ -22,6 +22,10 @@
> > > > * Authors: Christian König
> > > > */
> > > >
> > > > +#include <linux/dma-buf-map.h>
> > > > +#include <linux/io-mapping.h>
> > > > +#include <linux/scatterlist.h>
> > > > +
> > > > #include <drm/ttm/ttm_resource.h>
> > > > #include <drm/ttm/ttm_bo_driver.h>
> > > >
> > > > @@ -147,3 +151,165 @@ void ttm_resource_manager_debug(struct
> > > > ttm_resource_manager *man,
> > > > man->func->debug(man, p);
> > > > }
> > > > EXPORT_SYMBOL(ttm_resource_manager_debug);
> > > > +
> > > > +static void ttm_kmap_iter_iomap_map_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;
> > > > + }
> > > > +
> > > > + 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_kmap_iter_iomap_unmap_local(struct
> > > > ttm_kmap_iter *iter,
> > > > + struct dma_buf_map
> > > > *map)
> > > > +{
> > > > + io_mapping_unmap_local(map->vaddr_iomem);
> > > > +}
> > > > +
> > > > +static const struct ttm_kmap_iter_ops ttm_kmap_iter_io_ops = {
> > > > + .map_local = ttm_kmap_iter_iomap_map_local,
> > > > + .unmap_local = ttm_kmap_iter_iomap_unmap_local,
> > > > + .maps_tt = false,
> > > > +};
> > > > +
> > > > +/**
> > > > + * 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)
> > > > +{
> > > > + 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));
> > > > +
> > > > + return &iter_io->base;
> > > > +}
> > > > +EXPORT_SYMBOL(ttm_kmap_iter_iomap_init);
> > > > +
> > > > +/**
> > > > + * 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.
> > > > + */
> > > > +
> > > > +static void ttm_kmap_iter_linear_io_map_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 const struct ttm_kmap_iter_ops
> > > > ttm_kmap_iter_linear_io_ops = {
> > > > + .map_local = ttm_kmap_iter_linear_io_map_local,
> > > > + .maps_tt = false,
> > > > +};
> > > > +
> > > > +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)
> > > > +{
> > > > + int ret;
> > > > +
> > > > + ret = ttm_mem_io_reserve(bdev, mem);
> > > > + if (ret)
> > > > + goto out_err;
> > > > + if (!mem->bus.is_iomem) {
> > > > + ret = -EINVAL;
> > > > + goto out_io_free;
> > > > + }
> > > > +
> > > > + 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;
> > > > +
> > > > + 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));
> > > The comments in set_vaddr suggest that this is meant for
> > > system-memory. Does that actually matter or is it just about not
> > > losing the __iomem annotation on platforms where it matters?
> >
> > Yes, it's the latter. dma_buf_map() is relatively new and the
> > author
> > probably didn't think about the case of cached iomem, which is used
> > by,
> > for example, vmwgfx.
> >
> > > Apparently cached device local is a thing. Also should this not
> > > be
> > > wrapped in CONFIG_X86?
> >
> > Both dma_buf_map() and memremap are generic, I think, I guess
> > memremap
> > would return NULL if it's not supported.
>
> It looks like memremap just wraps ioremap_cache, but since it also
> discards the __iomem annotation should we be doing that universally?
> Also not sure if ioremap_cache is universally supported, so wrapping
> in CONFIG_X86 and falling back to plain ioremap() might be needed? Or
> at least that looks like roughly what the previous code was doing?
> Not
> too sure tbh.
>
I think the long term goal is to use memremap all over the place, to
just not have to bother with the __iomem annotation. But to do that io-
mapping.h needs to support memremap. But for now we need to be strict
about __iomem unless we're in arch specific code. That's why that
dma_buf_map thing was created, but TTM memcpy was never fully adapted.
As for limited arch support for memremap cached, It looks like we only
need to or in "backup" mapping modes in the memremap flags, and we'd
mimic the previous behaviour.
/Thomas
> >
> > /Thomas
> >
> >
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