>-----Original Message-----
>From: dri-devel <dri-devel-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of
>Christian König
>Sent: Wednesday, June 24, 2020 9:36 AM
>To: dri-devel@xxxxxxxxxxxxxxxxxxxxx
>Subject: [PATCH 2/2] drm/ttm: make TT creation purely optional
>
>We only need the page array when the BO is about to be accessed.
>
>So not only populate, but also create it on demand.
>
>Signed-off-by: Christian König <christian.koenig@xxxxxxx>
>---
> drivers/gpu/drm/ttm/ttm_bo.c | 26 ++++----------------------
> drivers/gpu/drm/ttm/ttm_bo_util.c | 9 +++++++--
> drivers/gpu/drm/ttm/ttm_bo_vm.c | 5 +++++
> 3 files changed, 16 insertions(+), 24 deletions(-)
>
>diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
>index 15f9b19fa00d..0e0a9dadf3ed 100644
>--- a/drivers/gpu/drm/ttm/ttm_bo.c
>+++ b/drivers/gpu/drm/ttm/ttm_bo.c
>@@ -667,13 +667,8 @@ static int ttm_bo_evict(struct ttm_buffer_object *bo,
> placement.num_busy_placement = 0;
> bdev->driver->evict_flags(bo, &placement);
>
>- if (!placement.num_placement &&
>!placement.num_busy_placement) {
>- ret = ttm_bo_pipeline_gutting(bo);
>- if (ret)
>- return ret;
>-
>- return ttm_tt_create(bo, false);
>- }
>+ if (!placement.num_placement &&
>!placement.num_busy_placement)
>+ return ttm_bo_pipeline_gutting(bo);
>
> evict_mem = bo->mem;
> evict_mem.mm_node = NULL;
>@@ -1200,13 +1195,8 @@ int ttm_bo_validate(struct ttm_buffer_object *bo,
> /*
> * Remove the backing store if no placement is given.
> */
>- if (!placement->num_placement && !placement-
>>num_busy_placement) {
>- ret = ttm_bo_pipeline_gutting(bo);
>- if (ret)
>- return ret;
>-
>- return ttm_tt_create(bo, false);
>- }
>+ if (!placement->num_placement && !placement-
>>num_busy_placement)
>+ return ttm_bo_pipeline_gutting(bo);
>
> /*
> * Check whether we need to move buffer.
>@@ -1223,14 +1213,6 @@ int ttm_bo_validate(struct ttm_buffer_object *bo,
> ttm_flag_masked(&bo->mem.placement, new_flags,
> ~TTM_PL_MASK_MEMTYPE);
> }
>- /*
>- * We might need to add a TTM.
>- */
>- if (bo->mem.mem_type == TTM_PL_SYSTEM && bo->ttm == NULL) {
>- ret = ttm_tt_create(bo, true);
>- if (ret)
>- return ret;
>- }
> return 0;
> }
> EXPORT_SYMBOL(ttm_bo_validate);
>diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c
>b/drivers/gpu/drm/ttm/ttm_bo_util.c
>index 52d2b71f1588..f8414f820350 100644
>--- a/drivers/gpu/drm/ttm/ttm_bo_util.c
>+++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
>@@ -580,12 +580,17 @@ static int ttm_bo_kmap_ttm(struct
>ttm_buffer_object *bo,
> .interruptible = false,
> .no_wait_gpu = false
> };
>- struct ttm_tt *ttm = bo->ttm;
>+ struct ttm_tt *ttm;
> pgprot_t prot;
> int ret;
>
>- BUG_ON(!ttm);
>+ if (!bo->ttm) {
>+ ret = ttm_tt_create(bo, true);
Would it be reasonable to move the NULL check into ttm_tt_create()?
Kind of an opposite path NULL check, but it makes the path a little
more clean.
Mike
>+ if (ret)
>+ return ret;
>+ }
>
>+ ttm = bo->ttm;
> ret = ttm_tt_populate(ttm, &ctx);
> if (ret)
> return ret;
>diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c
>b/drivers/gpu/drm/ttm/ttm_bo_vm.c
>index 0ad30b112982..bdfed6725d6f 100644
>--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
>+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
>@@ -349,6 +349,11 @@ vm_fault_t ttm_bo_vm_fault_reserved(struct
>vm_fault *vmf,
>
> };
>
>+ if (!bo->ttm && ttm_tt_create(bo, true)) {
>+ ret = VM_FAULT_OOM;
>+ goto out_io_unlock;
>+ }
>+
> ttm = bo->ttm;
> if (ttm_tt_populate(bo->ttm, &ctx)) {
> ret = VM_FAULT_OOM;
>--
>2.17.1
>
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