[Intel-gfx] [PATCH 1/2] drm/i915/ttm: Reorganize the ttm move code somewhat
Thomas Hellström
thomas.hellstrom at linux.intel.com
Wed Jun 30 15:27:19 UTC 2021
On Wed, 2021-06-30 at 15:19 +0100, Matthew Auld wrote:
> On Thu, 24 Jun 2021 at 20:31, Thomas Hellström
> <thomas.hellstrom at linux.intel.com> wrote:
> >
> > In order to make the code a bit more readable and to facilitate
> > async memcpy moves, reorganize the move code a little. Determine
> > at an early stage whether to copy or to clear.
> >
> > Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
> > ---
> > drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 70 ++++++++++++++-------
> > ----
> > 1 file changed, 40 insertions(+), 30 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> > b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> > index c39d982c4fa6..4e529adcdfc7 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> > @@ -431,6 +431,7 @@ i915_ttm_resource_get_st(struct
> > drm_i915_gem_object *obj,
> > }
> >
> > static int i915_ttm_accel_move(struct ttm_buffer_object *bo,
> > + bool clear,
> > struct ttm_resource *dst_mem,
> > struct sg_table *dst_st)
> > {
> > @@ -449,13 +450,10 @@ static int i915_ttm_accel_move(struct
> > ttm_buffer_object *bo,
> > return -EINVAL;
> >
> > dst_level = i915_ttm_cache_level(i915, dst_mem, ttm);
> > - if (!ttm || !ttm_tt_is_populated(ttm)) {
> > + if (clear) {
> > if (bo->type == ttm_bo_type_kernel)
> > return -EINVAL;
>
> Was that meant to be:
> return 0:
>
> ?
>
> Also does that mean we are incorrectly falling back to memset, for
> non-userspace objects, instead of making it a noop?
No, we're deliberately falling back to memset for non-userspace
objects, but the logic only memsets in the BO_ALLOC_CPU_CLEAR case if
everything is implemented correctly.
>
> >
> > - if (ttm && !(ttm->page_flags &
> > TTM_PAGE_FLAG_ZERO_ALLOC))
> > - return 0;
> > -
> > intel_engine_pm_get(i915->gt.migrate.context-
> > >engine);
> > ret = intel_context_migrate_clear(i915-
> > >gt.migrate.context, NULL,
> > dst_st->sgl,
> > dst_level,
> > @@ -489,27 +487,53 @@ static int i915_ttm_accel_move(struct
> > ttm_buffer_object *bo,
> > return ret;
> > }
> >
> > -static int i915_ttm_move(struct ttm_buffer_object *bo, bool evict,
> > - struct ttm_operation_ctx *ctx,
> > - struct ttm_resource *dst_mem,
> > - struct ttm_place *hop)
> > +static void __i915_ttm_move(struct ttm_buffer_object *bo, bool
> > clear,
> > + struct ttm_resource *dst_mem,
> > + struct sg_table *dst_st)
> > {
> > struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
> > - struct ttm_resource_manager *dst_man =
> > - ttm_manager_type(bo->bdev, dst_mem->mem_type);
> > struct intel_memory_region *dst_reg, *src_reg;
> > union {
> > struct ttm_kmap_iter_tt tt;
> > struct ttm_kmap_iter_iomap io;
> > } _dst_iter, _src_iter;
> > struct ttm_kmap_iter *dst_iter, *src_iter;
> > - struct sg_table *dst_st;
> > int ret;
> >
> > dst_reg = i915_ttm_region(bo->bdev, dst_mem->mem_type);
> > src_reg = i915_ttm_region(bo->bdev, bo->resource-
> > >mem_type);
> > GEM_BUG_ON(!dst_reg || !src_reg);
> >
> > + ret = i915_ttm_accel_move(bo, clear, dst_mem, dst_st);
> > + if (ret) {
>
> One future consideration is flat CCS where I don't think we can
> easily
> fall back to memcpy for userspace objects. Maybe we can make this
> fallback conditional on DG1 or !ALLOC_USER for now, or just add a
> TODO?
Ugh. Is that true for both clearing and copying, or is it only copying?
Problem is if we hit an engine reset and fence error during initial
clearing / swapin, the plan moving forward is to intercept that and
resort to cpu clearing / copying for security reasons. In the worst
case we at least need to be able to clear.
/Thomas
>
> > + dst_iter = !cpu_maps_iomem(dst_mem) ?
> > + ttm_kmap_iter_tt_init(&_dst_iter.tt, bo-
> > >ttm) :
> > + ttm_kmap_iter_iomap_init(&_dst_iter.io,
> > &dst_reg->iomap,
> > + dst_st, dst_reg-
> > >region.start);
> > +
> > + src_iter = !cpu_maps_iomem(bo->resource) ?
> > + ttm_kmap_iter_tt_init(&_src_iter.tt, bo-
> > >ttm) :
> > + ttm_kmap_iter_iomap_init(&_src_iter.io,
> > &src_reg->iomap,
> > + obj-
> > >ttm.cached_io_st,
> > + src_reg-
> > >region.start);
> > +
> > + ttm_move_memcpy(bo, dst_mem->num_pages, dst_iter,
> > src_iter);
> > + }
> > +}
> > +
> > +static int i915_ttm_move(struct ttm_buffer_object *bo, bool evict,
> > + struct ttm_operation_ctx *ctx,
> > + struct ttm_resource *dst_mem,
> > + struct ttm_place *hop)
> > +{
> > + struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
> > + struct ttm_resource_manager *dst_man =
> > + ttm_manager_type(bo->bdev, dst_mem->mem_type);
> > + struct ttm_tt *ttm = bo->ttm;
> > + struct sg_table *dst_st;
> > + bool clear;
> > + int ret;
> > +
> > /* Sync for now. We could do the actual copy async. */
> > ret = ttm_bo_wait_ctx(bo, ctx);
> > if (ret)
> > @@ -526,9 +550,8 @@ static int i915_ttm_move(struct
> > ttm_buffer_object *bo, bool evict,
> > }
> >
> > /* Populate ttm with pages if needed. Typically system
> > memory. */
> > - if (bo->ttm && (dst_man->use_tt ||
> > - (bo->ttm->page_flags &
> > TTM_PAGE_FLAG_SWAPPED))) {
> > - ret = ttm_tt_populate(bo->bdev, bo->ttm, ctx);
> > + if (ttm && (dst_man->use_tt || (ttm->page_flags &
> > TTM_PAGE_FLAG_SWAPPED))) {
> > + ret = ttm_tt_populate(bo->bdev, ttm, ctx);
> > if (ret)
> > return ret;
> > }
> > @@ -537,23 +560,10 @@ static int i915_ttm_move(struct
> > ttm_buffer_object *bo, bool evict,
> > if (IS_ERR(dst_st))
> > return PTR_ERR(dst_st);
> >
> > - ret = i915_ttm_accel_move(bo, dst_mem, dst_st);
> > - if (ret) {
> > - /* If we start mapping GGTT, we can no longer use
> > man::use_tt here. */
> > - dst_iter = !cpu_maps_iomem(dst_mem) ?
> > - ttm_kmap_iter_tt_init(&_dst_iter.tt, bo-
> > >ttm) :
> > - ttm_kmap_iter_iomap_init(&_dst_iter.io,
> > &dst_reg->iomap,
> > - dst_st, dst_reg-
> > >region.start);
> > -
> > - src_iter = !cpu_maps_iomem(bo->resource) ?
> > - ttm_kmap_iter_tt_init(&_src_iter.tt, bo-
> > >ttm) :
> > - ttm_kmap_iter_iomap_init(&_src_iter.io,
> > &src_reg->iomap,
> > - obj-
> > >ttm.cached_io_st,
> > - src_reg-
> > >region.start);
> > + clear = !cpu_maps_iomem(bo->resource) && (!ttm ||
> > !ttm_tt_is_populated(ttm));
> > + if (!(clear && ttm && !(ttm->page_flags &
> > TTM_PAGE_FLAG_ZERO_ALLOC)))
>
> Seems quite hard to read?
>
> Reviewed-by: Matthew Auld <matthew.auld at intel.com>
>
>
> > + __i915_ttm_move(bo, clear, dst_mem, dst_st);
> >
> > - ttm_move_memcpy(bo, dst_mem->num_pages, dst_iter,
> > src_iter);
> > - }
> > - /* Below dst_mem becomes bo->resource. */
> > ttm_bo_move_sync_cleanup(bo, dst_mem);
> > i915_ttm_adjust_domains_after_move(obj);
> > i915_ttm_free_cached_io_st(obj);
> > --
> > 2.31.1
> >
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