On Mon, 29 Nov 2021 at 13:57, Maarten Lankhorst
<maarten.lankhorst@xxxxxxxxxxxxxxx> wrote:
>
> In the next commit, we don't evict when refcount = 0.
>
> igt_vm_isolation() continuously tries to pin/unpin at same address,
> but also calls put() on the object, which means the object may not
> be unpinned in time.
>
> Instead of this, re-use the same object over and over, so they can
> be unbound as required.
>
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
Is this something to be worried about in the real world, outside of
the selftests?
> ---
> .../drm/i915/gem/selftests/i915_gem_context.c | 54 +++++++++++--------
> 1 file changed, 32 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
> index b32f7fed2d9c..3fc595b57cf4 100644
> --- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
> @@ -1481,10 +1481,10 @@ static int check_scratch(struct i915_address_space *vm, u64 offset)
>
> static int write_to_scratch(struct i915_gem_context *ctx,
> struct intel_engine_cs *engine,
> + struct drm_i915_gem_object *obj,
> u64 offset, u32 value)
> {
> struct drm_i915_private *i915 = ctx->i915;
> - struct drm_i915_gem_object *obj;
> struct i915_address_space *vm;
> struct i915_request *rq;
> struct i915_vma *vma;
> @@ -1497,15 +1497,9 @@ static int write_to_scratch(struct i915_gem_context *ctx,
> if (err)
> return err;
>
> - obj = i915_gem_object_create_internal(i915, PAGE_SIZE);
> - if (IS_ERR(obj))
> - return PTR_ERR(obj);
> -
> cmd = i915_gem_object_pin_map_unlocked(obj, I915_MAP_WB);
> - if (IS_ERR(cmd)) {
> - err = PTR_ERR(cmd);
> - goto out;
> - }
> + if (IS_ERR(cmd))
> + return PTR_ERR(cmd);
>
> *cmd++ = MI_STORE_DWORD_IMM_GEN4;
> if (GRAPHICS_VER(i915) >= 8) {
> @@ -1569,17 +1563,19 @@ static int write_to_scratch(struct i915_gem_context *ctx,
> i915_vma_unpin(vma);
> out_vm:
> i915_vm_put(vm);
> -out:
> - i915_gem_object_put(obj);
> +
> + if (!err)
> + err = i915_gem_object_wait(obj, 0, MAX_SCHEDULE_TIMEOUT);
> +
> return err;
> }
>
> static int read_from_scratch(struct i915_gem_context *ctx,
> struct intel_engine_cs *engine,
> + struct drm_i915_gem_object *obj,
> u64 offset, u32 *value)
> {
> struct drm_i915_private *i915 = ctx->i915;
> - struct drm_i915_gem_object *obj;
> struct i915_address_space *vm;
> const u32 result = 0x100;
> struct i915_request *rq;
> @@ -1594,10 +1590,6 @@ static int read_from_scratch(struct i915_gem_context *ctx,
> if (err)
> return err;
>
> - obj = i915_gem_object_create_internal(i915, PAGE_SIZE);
> - if (IS_ERR(obj))
> - return PTR_ERR(obj);
> -
> if (GRAPHICS_VER(i915) >= 8) {
> const u32 GPR0 = engine->mmio_base + 0x600;
>
> @@ -1615,7 +1607,7 @@ static int read_from_scratch(struct i915_gem_context *ctx,
> cmd = i915_gem_object_pin_map_unlocked(obj, I915_MAP_WB);
> if (IS_ERR(cmd)) {
> err = PTR_ERR(cmd);
> - goto out;
> + goto err_unpin;
> }
>
> memset(cmd, POISON_INUSE, PAGE_SIZE);
> @@ -1651,7 +1643,7 @@ static int read_from_scratch(struct i915_gem_context *ctx,
> cmd = i915_gem_object_pin_map_unlocked(obj, I915_MAP_WB);
> if (IS_ERR(cmd)) {
> err = PTR_ERR(cmd);
> - goto out;
> + goto err_unpin;
> }
>
> memset(cmd, POISON_INUSE, PAGE_SIZE);
> @@ -1722,8 +1714,10 @@ static int read_from_scratch(struct i915_gem_context *ctx,
> i915_vma_unpin(vma);
> out_vm:
> i915_vm_put(vm);
> -out:
> - i915_gem_object_put(obj);
> +
> + if (!err)
> + err = i915_gem_object_wait(obj, 0, MAX_SCHEDULE_TIMEOUT);
> +
> return err;
> }
>
> @@ -1765,6 +1759,7 @@ static int igt_vm_isolation(void *arg)
> u64 vm_total;
> u32 expected;
> int err;
> + struct drm_i915_gem_object *obj_a, *obj_b;
Nit: Christmas tree-ish
>
> if (GRAPHICS_VER(i915) < 7)
> return 0;
> @@ -1810,6 +1805,18 @@ static int igt_vm_isolation(void *arg)
> vm_total = ctx_a->vm->total;
> GEM_BUG_ON(ctx_b->vm->total != vm_total);
>
> + obj_a = i915_gem_object_create_internal(i915, PAGE_SIZE);
> + if (IS_ERR(obj_a)) {
> + err = PTR_ERR(obj_a);
> + goto out_file;
> + }
> +
> + obj_b = i915_gem_object_create_internal(i915, PAGE_SIZE);
> + if (IS_ERR(obj_b)) {
> + err = PTR_ERR(obj_b);
> + goto put_a;
> + }
> +
> count = 0;
> num_engines = 0;
> for_each_uabi_engine(engine, i915) {
> @@ -1832,10 +1839,10 @@ static int igt_vm_isolation(void *arg)
> I915_GTT_PAGE_SIZE, vm_total,
> sizeof(u32), alignof_dword);
>
> - err = write_to_scratch(ctx_a, engine,
> + err = write_to_scratch(ctx_a, engine, obj_a,
> offset, 0xdeadbeef);
> if (err == 0)
> - err = read_from_scratch(ctx_b, engine,
> + err = read_from_scratch(ctx_b, engine, obj_b,
> offset, &value);
> if (err)
> goto out_file;
goto put_b; below also?
Otherwise,
Reviewed-by: Matthew Auld <matthew.auld@xxxxxxxxx>
> @@ -1858,6 +1865,9 @@ static int igt_vm_isolation(void *arg)
> pr_info("Checked %lu scratch offsets across %lu engines\n",
> count, num_engines);
>
> + i915_gem_object_put(obj_b);
> +put_a:
> + i915_gem_object_put(obj_a);
> out_file:
> if (igt_live_test_end(&t))
> err = -EIO;
> --
> 2.34.0
>
