Quoting Mika Kuoppala (2020-04-24 17:01:49)
> Indirect ctx batchbuffers are a hw feature of which
> batch can be run, by hardware, during context restoration stage.
> Driver can setup a batchbuffer and also an offset into the
> context image. When context image is marshalled from
> memory to registers, and when the offset from the start of
> context register state is equal of what driver pre-determined,
> batch will run. So one can manipulate context restoration
> process at cacheline granularity, given some limitations,
> as you need to have rudimentaries in place before you can
> run a batch.
>
> Add selftest which will write the ring start register
> to a canary spot. This will test that hardware will run a
> batchbuffer for the context in question.
>
> v2: request wait fix, naming (Chris)
>
> Signed-off-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
I'd still squash this with the user; so we have the check on the
interface along with it.
> ---
> drivers/gpu/drm/i915/gt/selftest_lrc.c | 153 ++++++++++++++++++++++++-
> 1 file changed, 152 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/selftest_lrc.c b/drivers/gpu/drm/i915/gt/selftest_lrc.c
> index 4996d511f6fc..89a3bbf72a7a 100644
> --- a/drivers/gpu/drm/i915/gt/selftest_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/selftest_lrc.c
> @@ -5710,6 +5710,156 @@ static int live_lrc_isolation(void *arg)
> return err;
> }
>
> +static int indirect_ctx_submit_req(struct intel_context *ce)
> +{
> + struct i915_request *rq;
> + int err = 0;
> +
> + rq = intel_context_create_request(ce);
> + if (IS_ERR(rq))
> + return PTR_ERR(rq);
> +
> + i915_request_get(rq);
> + i915_request_add(rq);
> +
> + if (i915_request_wait(rq, 0, HZ / 5) < 0)
> + err = -ETIME;
> +
> + i915_request_put(rq);
> +
> + return err;
> +}
> +
> +#define CTX_BB_CANARY_OFFSET (3*1024)
> +#define CTX_BB_CANARY_INDEX (CTX_BB_CANARY_OFFSET/sizeof(u32))
> +
> +static u32 *
> +emit_indirect_ctx_bb_canary(struct intel_context *ce, u32 *cs)
> +{
> + const u32 ring_start_reg = i915_mmio_reg_offset(RING_START(0));
> + const u32 srm = MI_STORE_REGISTER_MEM_GEN8 |
> + MI_SRM_LRM_GLOBAL_GTT | MI_LRI_LRM_CS_MMIO;
> +
> + *cs++ = srm;
> + *cs++ = ring_start_reg;
> + *cs++ = i915_ggtt_offset(ce->state) +
> + ce->ctx_bb_offset + CTX_BB_CANARY_OFFSET;
> + *cs++ = 0;
> +
> + return cs;
> +}
> +
> +static void
> +indirect_ctx_bb_setup(struct intel_context *ce)
> +{
> + u32 *cs = context_indirect_bb(ce);
> +
> + cs[CTX_BB_CANARY_INDEX] = 0xdeadf00d;
> +
> + setup_indirect_ctx_bb(ce, emit_indirect_ctx_bb_canary);
> +}
> +
> +static bool check_ring_start(struct intel_context *ce)
> +{
> + const u32 * const ctx_bb = (void *)(ce->lrc_reg_state) -
> + LRC_STATE_OFFSET + ce->ctx_bb_offset;
> +
> + if (ctx_bb[CTX_BB_CANARY_INDEX] == ce->lrc_reg_state[CTX_RING_START])
> + return true;
> +
> + pr_err("ring start mismatch: canary 0x%08x vs state 0x%08x\n",
> + ctx_bb[CTX_BB_CANARY_INDEX],
> + ce->lrc_reg_state[CTX_RING_START]);
> +
> + return false;
> +}
> +
> +static int indirect_ctx_bb_check(struct intel_context *ce)
> +{
> + int err;
> +
> + err = indirect_ctx_submit_req(ce);
> + if (err)
> + return err;
> +
> + if (!check_ring_start(ce))
> + return -EINVAL;
> +
> + return 0;
> +}
> +
> +static int __live_lrc_indirect_ctx_bb(struct intel_engine_cs *engine)
> +{
> + struct intel_context *a, *b;
> + int err = 0;
> +
> + a = intel_context_create(engine);
> + b = intel_context_create(engine);
> +
> + err = intel_context_pin(a);
> + if (err)
> + return err;
> +
> + err = intel_context_pin(b);
> + if (err) {
> + intel_context_put(a);
> + return err;
> + }
> +
> + /* We use the already reserved extra page in context state */
> + if (!a->ctx_bb_offset) {
> + GEM_BUG_ON(b->ctx_bb_offset);
> + GEM_BUG_ON(INTEL_GEN(engine->i915) == 12);
> + goto out;
> + }
> +
> + /* In order to test that our per context bb is truly per context,
> + * and executes at the intended spot on context restoring process,
> + * make the batch store the ring start value to memory.
> + * As ring start is restored apriori of starting the indirect ctx bb and
> + * as it will be different for each context, it fits to this purpose.
> + */
> + indirect_ctx_bb_setup(a);
> + indirect_ctx_bb_setup(b);
> +
> + err = indirect_ctx_bb_check(a);
> + if (err)
> + goto out;
> +
> + err = indirect_ctx_bb_check(b);
> +out:
> + intel_context_unpin(b);
> + intel_context_put(b);
> +
> + intel_context_unpin(a);
> + intel_context_put(a);
> +
> + return err;
> +}
> +
> +static int live_lrc_indirect_ctx_bb(void *arg)
> +{
> + struct intel_gt *gt = arg;
> + struct intel_engine_cs *engine;
> + enum intel_engine_id id;
> + int err = 0;
> +
> + for_each_engine(engine, gt, id) {
> +
> + intel_engine_pm_get(engine);
> + err = __live_lrc_indirect_ctx_bb(engine);
> + intel_engine_pm_put(engine);
> +
> + if (igt_flush_test(gt->i915))
> + err = -EIO;
> +
> + if (err)
> + break;
> + }
> +
> + return err;
> +}
> +
> static void garbage_reset(struct intel_engine_cs *engine,
> struct i915_request *rq)
> {
> @@ -5941,10 +6091,11 @@ int intel_lrc_live_selftests(struct drm_i915_private *i915)
> SUBTEST(live_lrc_fixed),
> SUBTEST(live_lrc_state),
> SUBTEST(live_lrc_gpr),
> - SUBTEST(live_lrc_isolation),
> + SUBTEST(live_lrc_indirect_ctx_bb),
> SUBTEST(live_lrc_timestamp),
> SUBTEST(live_lrc_garbage),
> SUBTEST(live_pphwsp_runtime),
> + SUBTEST(live_lrc_isolation),
For final; I'd keep isolation early, it's a rough sequence of severity.
Acked-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
-Chris
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