On Thu, May 27, 2021 at 11:26:46AM -0500, Jason Ekstrand wrote:
> When the APIs were added to manage VMs more directly from userspace, the
> questionable choice was made to allow changing out the VM on a context
> at any time. This is horribly racy and there's absolutely no reason why
> any userspace would want to do this outside of testing that exact race.
> By removing support for CONTEXT_PARAM_VM from ctx_setparam, we make it
> impossible to change out the VM after the context has been fully
> created. This lets us delete a bunch of deferred task code as well as a
> duplicated (and slightly different) copy of the code which programs the
> PPGTT registers.
>
> v2 (Jason Ekstrand):
> - Expand the commit message
>
> Signed-off-by: Jason Ekstrand <jason@xxxxxxxxxxxxxx>
Already scored an Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
now that the commit message is there.
-Daniel
> ---
> drivers/gpu/drm/i915/gem/i915_gem_context.c | 262 ------------------
> .../gpu/drm/i915/gem/i915_gem_context_types.h | 2 +-
> .../drm/i915/gem/selftests/i915_gem_context.c | 119 --------
> .../drm/i915/selftests/i915_mock_selftests.h | 1 -
> 4 files changed, 1 insertion(+), 383 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> index f7c83730ee07f..a528c8f3354a0 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> @@ -1633,120 +1633,6 @@ int i915_gem_vm_destroy_ioctl(struct drm_device *dev, void *data,
> return 0;
> }
>
> -struct context_barrier_task {
> - struct i915_active base;
> - void (*task)(void *data);
> - void *data;
> -};
> -
> -static void cb_retire(struct i915_active *base)
> -{
> - struct context_barrier_task *cb = container_of(base, typeof(*cb), base);
> -
> - if (cb->task)
> - cb->task(cb->data);
> -
> - i915_active_fini(&cb->base);
> - kfree(cb);
> -}
> -
> -I915_SELFTEST_DECLARE(static intel_engine_mask_t context_barrier_inject_fault);
> -static int context_barrier_task(struct i915_gem_context *ctx,
> - intel_engine_mask_t engines,
> - bool (*skip)(struct intel_context *ce, void *data),
> - int (*pin)(struct intel_context *ce, struct i915_gem_ww_ctx *ww, void *data),
> - int (*emit)(struct i915_request *rq, void *data),
> - void (*task)(void *data),
> - void *data)
> -{
> - struct context_barrier_task *cb;
> - struct i915_gem_engines_iter it;
> - struct i915_gem_engines *e;
> - struct i915_gem_ww_ctx ww;
> - struct intel_context *ce;
> - int err = 0;
> -
> - GEM_BUG_ON(!task);
> -
> - cb = kmalloc(sizeof(*cb), GFP_KERNEL);
> - if (!cb)
> - return -ENOMEM;
> -
> - i915_active_init(&cb->base, NULL, cb_retire, 0);
> - err = i915_active_acquire(&cb->base);
> - if (err) {
> - kfree(cb);
> - return err;
> - }
> -
> - e = __context_engines_await(ctx, NULL);
> - if (!e) {
> - i915_active_release(&cb->base);
> - return -ENOENT;
> - }
> -
> - for_each_gem_engine(ce, e, it) {
> - struct i915_request *rq;
> -
> - if (I915_SELFTEST_ONLY(context_barrier_inject_fault &
> - ce->engine->mask)) {
> - err = -ENXIO;
> - break;
> - }
> -
> - if (!(ce->engine->mask & engines))
> - continue;
> -
> - if (skip && skip(ce, data))
> - continue;
> -
> - i915_gem_ww_ctx_init(&ww, true);
> -retry:
> - err = intel_context_pin_ww(ce, &ww);
> - if (err)
> - goto err;
> -
> - if (pin)
> - err = pin(ce, &ww, data);
> - if (err)
> - goto err_unpin;
> -
> - rq = i915_request_create(ce);
> - if (IS_ERR(rq)) {
> - err = PTR_ERR(rq);
> - goto err_unpin;
> - }
> -
> - err = 0;
> - if (emit)
> - err = emit(rq, data);
> - if (err == 0)
> - err = i915_active_add_request(&cb->base, rq);
> -
> - i915_request_add(rq);
> -err_unpin:
> - intel_context_unpin(ce);
> -err:
> - if (err == -EDEADLK) {
> - err = i915_gem_ww_ctx_backoff(&ww);
> - if (!err)
> - goto retry;
> - }
> - i915_gem_ww_ctx_fini(&ww);
> -
> - if (err)
> - break;
> - }
> - i915_sw_fence_complete(&e->fence);
> -
> - cb->task = err ? NULL : task; /* caller needs to unwind instead */
> - cb->data = data;
> -
> - i915_active_release(&cb->base);
> -
> - return err;
> -}
> -
> static int get_ppgtt(struct drm_i915_file_private *file_priv,
> struct i915_gem_context *ctx,
> struct drm_i915_gem_context_param *args)
> @@ -1779,150 +1665,6 @@ static int get_ppgtt(struct drm_i915_file_private *file_priv,
> return err;
> }
>
> -static void set_ppgtt_barrier(void *data)
> -{
> - struct i915_address_space *old = data;
> -
> - if (INTEL_GEN(old->i915) < 8)
> - gen6_ppgtt_unpin_all(i915_vm_to_ppgtt(old));
> -
> - i915_vm_close(old);
> -}
> -
> -static int pin_ppgtt_update(struct intel_context *ce, struct i915_gem_ww_ctx *ww, void *data)
> -{
> - struct i915_address_space *vm = ce->vm;
> -
> - if (!HAS_LOGICAL_RING_CONTEXTS(vm->i915))
> - /* ppGTT is not part of the legacy context image */
> - return gen6_ppgtt_pin(i915_vm_to_ppgtt(vm), ww);
> -
> - return 0;
> -}
> -
> -static int emit_ppgtt_update(struct i915_request *rq, void *data)
> -{
> - struct i915_address_space *vm = rq->context->vm;
> - struct intel_engine_cs *engine = rq->engine;
> - u32 base = engine->mmio_base;
> - u32 *cs;
> - int i;
> -
> - if (i915_vm_is_4lvl(vm)) {
> - struct i915_ppgtt *ppgtt = i915_vm_to_ppgtt(vm);
> - const dma_addr_t pd_daddr = px_dma(ppgtt->pd);
> -
> - cs = intel_ring_begin(rq, 6);
> - if (IS_ERR(cs))
> - return PTR_ERR(cs);
> -
> - *cs++ = MI_LOAD_REGISTER_IMM(2);
> -
> - *cs++ = i915_mmio_reg_offset(GEN8_RING_PDP_UDW(base, 0));
> - *cs++ = upper_32_bits(pd_daddr);
> - *cs++ = i915_mmio_reg_offset(GEN8_RING_PDP_LDW(base, 0));
> - *cs++ = lower_32_bits(pd_daddr);
> -
> - *cs++ = MI_NOOP;
> - intel_ring_advance(rq, cs);
> - } else if (HAS_LOGICAL_RING_CONTEXTS(engine->i915)) {
> - struct i915_ppgtt *ppgtt = i915_vm_to_ppgtt(vm);
> - int err;
> -
> - /* Magic required to prevent forcewake errors! */
> - err = engine->emit_flush(rq, EMIT_INVALIDATE);
> - if (err)
> - return err;
> -
> - cs = intel_ring_begin(rq, 4 * GEN8_3LVL_PDPES + 2);
> - if (IS_ERR(cs))
> - return PTR_ERR(cs);
> -
> - *cs++ = MI_LOAD_REGISTER_IMM(2 * GEN8_3LVL_PDPES) | MI_LRI_FORCE_POSTED;
> - for (i = GEN8_3LVL_PDPES; i--; ) {
> - const dma_addr_t pd_daddr = i915_page_dir_dma_addr(ppgtt, i);
> -
> - *cs++ = i915_mmio_reg_offset(GEN8_RING_PDP_UDW(base, i));
> - *cs++ = upper_32_bits(pd_daddr);
> - *cs++ = i915_mmio_reg_offset(GEN8_RING_PDP_LDW(base, i));
> - *cs++ = lower_32_bits(pd_daddr);
> - }
> - *cs++ = MI_NOOP;
> - intel_ring_advance(rq, cs);
> - }
> -
> - return 0;
> -}
> -
> -static bool skip_ppgtt_update(struct intel_context *ce, void *data)
> -{
> - if (HAS_LOGICAL_RING_CONTEXTS(ce->engine->i915))
> - return !ce->state;
> - else
> - return !atomic_read(&ce->pin_count);
> -}
> -
> -static int set_ppgtt(struct drm_i915_file_private *file_priv,
> - struct i915_gem_context *ctx,
> - struct drm_i915_gem_context_param *args)
> -{
> - struct i915_address_space *vm, *old;
> - int err;
> -
> - if (args->size)
> - return -EINVAL;
> -
> - if (!rcu_access_pointer(ctx->vm))
> - return -ENODEV;
> -
> - if (upper_32_bits(args->value))
> - return -ENOENT;
> -
> - vm = i915_gem_vm_lookup(file_priv, args->value);
> - if (!vm)
> - return -ENOENT;
> -
> - err = mutex_lock_interruptible(&ctx->mutex);
> - if (err)
> - goto out;
> -
> - if (i915_gem_context_is_closed(ctx)) {
> - err = -ENOENT;
> - goto unlock;
> - }
> -
> - if (vm == rcu_access_pointer(ctx->vm))
> - goto unlock;
> -
> - old = __set_ppgtt(ctx, vm);
> -
> - /* Teardown the existing obj:vma cache, it will have to be rebuilt. */
> - lut_close(ctx);
> -
> - /*
> - * We need to flush any requests using the current ppgtt before
> - * we release it as the requests do not hold a reference themselves,
> - * only indirectly through the context.
> - */
> - err = context_barrier_task(ctx, ALL_ENGINES,
> - skip_ppgtt_update,
> - pin_ppgtt_update,
> - emit_ppgtt_update,
> - set_ppgtt_barrier,
> - old);
> - if (err) {
> - i915_vm_close(__set_ppgtt(ctx, old));
> - i915_vm_close(old);
> - lut_close(ctx); /* force a rebuild of the old obj:vma cache */
> - }
> -
> -unlock:
> - mutex_unlock(&ctx->mutex);
> -out:
> - i915_vm_put(vm);
> - return err;
> -}
> -
> int
> i915_gem_user_to_context_sseu(struct intel_gt *gt,
> const struct drm_i915_gem_context_param_sseu *user,
> @@ -2458,10 +2200,6 @@ static int ctx_setparam(struct drm_i915_file_private *fpriv,
> ret = set_sseu(ctx, args);
> break;
>
> - case I915_CONTEXT_PARAM_VM:
> - ret = set_ppgtt(fpriv, ctx, args);
> - break;
> -
> case I915_CONTEXT_PARAM_ENGINES:
> ret = set_engines(ctx, args);
> break;
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context_types.h b/drivers/gpu/drm/i915/gem/i915_gem_context_types.h
> index b673061f4f5ba..84c821cca1739 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_context_types.h
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_context_types.h
> @@ -262,7 +262,7 @@ struct i915_gem_context {
> * In other modes, this is a NULL pointer with the expectation that
> * the caller uses the shared global GTT.
> */
> - struct i915_address_space __rcu *vm;
> + struct i915_address_space *vm;
>
> /**
> * @pid: process id of creator
> 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 ce70d0a3afb26..506cd9e9d4b25 100644
> --- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
> @@ -1875,125 +1875,6 @@ static int igt_vm_isolation(void *arg)
> return err;
> }
>
> -static bool skip_unused_engines(struct intel_context *ce, void *data)
> -{
> - return !ce->state;
> -}
> -
> -static void mock_barrier_task(void *data)
> -{
> - unsigned int *counter = data;
> -
> - ++*counter;
> -}
> -
> -static int mock_context_barrier(void *arg)
> -{
> -#undef pr_fmt
> -#define pr_fmt(x) "context_barrier_task():" # x
> - struct drm_i915_private *i915 = arg;
> - struct i915_gem_context *ctx;
> - struct i915_request *rq;
> - unsigned int counter;
> - int err;
> -
> - /*
> - * The context barrier provides us with a callback after it emits
> - * a request; useful for retiring old state after loading new.
> - */
> -
> - ctx = mock_context(i915, "mock");
> - if (!ctx)
> - return -ENOMEM;
> -
> - counter = 0;
> - err = context_barrier_task(ctx, 0, NULL, NULL, NULL,
> - mock_barrier_task, &counter);
> - if (err) {
> - pr_err("Failed at line %d, err=%d\n", __LINE__, err);
> - goto out;
> - }
> - if (counter == 0) {
> - pr_err("Did not retire immediately with 0 engines\n");
> - err = -EINVAL;
> - goto out;
> - }
> -
> - counter = 0;
> - err = context_barrier_task(ctx, ALL_ENGINES, skip_unused_engines,
> - NULL, NULL, mock_barrier_task, &counter);
> - if (err) {
> - pr_err("Failed at line %d, err=%d\n", __LINE__, err);
> - goto out;
> - }
> - if (counter == 0) {
> - pr_err("Did not retire immediately for all unused engines\n");
> - err = -EINVAL;
> - goto out;
> - }
> -
> - rq = igt_request_alloc(ctx, i915->gt.engine[RCS0]);
> - if (IS_ERR(rq)) {
> - pr_err("Request allocation failed!\n");
> - goto out;
> - }
> - i915_request_add(rq);
> -
> - counter = 0;
> - context_barrier_inject_fault = BIT(RCS0);
> - err = context_barrier_task(ctx, ALL_ENGINES, NULL, NULL, NULL,
> - mock_barrier_task, &counter);
> - context_barrier_inject_fault = 0;
> - if (err == -ENXIO)
> - err = 0;
> - else
> - pr_err("Did not hit fault injection!\n");
> - if (counter != 0) {
> - pr_err("Invoked callback on error!\n");
> - err = -EIO;
> - }
> - if (err)
> - goto out;
> -
> - counter = 0;
> - err = context_barrier_task(ctx, ALL_ENGINES, skip_unused_engines,
> - NULL, NULL, mock_barrier_task, &counter);
> - if (err) {
> - pr_err("Failed at line %d, err=%d\n", __LINE__, err);
> - goto out;
> - }
> - mock_device_flush(i915);
> - if (counter == 0) {
> - pr_err("Did not retire on each active engines\n");
> - err = -EINVAL;
> - goto out;
> - }
> -
> -out:
> - mock_context_close(ctx);
> - return err;
> -#undef pr_fmt
> -#define pr_fmt(x) x
> -}
> -
> -int i915_gem_context_mock_selftests(void)
> -{
> - static const struct i915_subtest tests[] = {
> - SUBTEST(mock_context_barrier),
> - };
> - struct drm_i915_private *i915;
> - int err;
> -
> - i915 = mock_gem_device();
> - if (!i915)
> - return -ENOMEM;
> -
> - err = i915_subtests(tests, i915);
> -
> - mock_destroy_device(i915);
> - return err;
> -}
> -
> int i915_gem_context_live_selftests(struct drm_i915_private *i915)
> {
> static const struct i915_subtest tests[] = {
> diff --git a/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h b/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h
> index 3db34d3eea58a..52aa91716dc1f 100644
> --- a/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h
> +++ b/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h
> @@ -32,6 +32,5 @@ selftest(vma, i915_vma_mock_selftests)
> selftest(evict, i915_gem_evict_mock_selftests)
> selftest(gtt, i915_gem_gtt_mock_selftests)
> selftest(hugepages, i915_gem_huge_page_mock_selftests)
> -selftest(contexts, i915_gem_context_mock_selftests)
> selftest(buddy, i915_buddy_mock_selftests)
> selftest(memory_region, intel_memory_region_mock_selftests)
> --
> 2.31.1
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
