Quoting Tvrtko Ursulin (2019-10-10 13:31:04)
>
> On 10/10/2019 12:02, Chris Wilson wrote:
> > Make sure that we copy across the registers from one engine to the next,
> > as we hop around a virtual engine.
> >
> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> > ---
> > Skip the test on gen8 as the context image is devoid of CS_GPR.
> > ---
> > drivers/gpu/drm/i915/gt/selftest_lrc.c | 180 +++++++++++++++++++++++++
> > 1 file changed, 180 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/gt/selftest_lrc.c b/drivers/gpu/drm/i915/gt/selftest_lrc.c
> > index 198cf2f754f4..9ee1fdd16aff 100644
> > --- a/drivers/gpu/drm/i915/gt/selftest_lrc.c
> > +++ b/drivers/gpu/drm/i915/gt/selftest_lrc.c
> > @@ -1952,6 +1952,33 @@ static int live_virtual_engine(void *arg)
> > return 0;
> > }
> >
> > +static struct i915_vma *create_scratch(struct intel_gt *gt)
> > +{
> > + struct drm_i915_gem_object *obj;
> > + struct i915_vma *vma;
> > + int err;
> > +
> > + obj = i915_gem_object_create_internal(gt->i915, PAGE_SIZE);
> > + if (IS_ERR(obj))
> > + return ERR_CAST(obj);
> > +
> > + i915_gem_object_set_cache_coherency(obj, I915_CACHING_CACHED);
> > +
> > + vma = i915_vma_instance(obj, >->ggtt->vm, NULL);
> > + if (IS_ERR(vma)) {
> > + i915_gem_object_put(obj);
> > + return vma;
> > + }
> > +
> > + err = i915_vma_pin(vma, 0, 0, PIN_GLOBAL);
> > + if (err) {
> > + i915_gem_object_put(obj);
> > + return ERR_PTR(err);
> > + }
> > +
> > + return vma;
> > +}
> > +
> > static int mask_virtual_engine(struct drm_i915_private *i915,
> > struct intel_engine_cs **siblings,
> > unsigned int nsibling)
> > @@ -2076,6 +2103,158 @@ static int live_virtual_mask(void *arg)
> > return 0;
> > }
> >
> > +static int preserved_virtual_engine(struct drm_i915_private *i915,
> > + struct intel_engine_cs **siblings,
> > + unsigned int nsibling)
> > +{
> > +#define CS_GPR(engine, n) ((engine)->mmio_base + 0x600 + (n) * 4)
> > +
> > + struct i915_request *last = NULL;
> > + struct i915_gem_context *ctx;
> > + struct intel_context *ve;
> > + struct i915_vma *scratch;
> > + struct igt_live_test t;
> > + const int num_gpr = 16 * 2; /* each GPR is 2 dwords */
> > + unsigned int n;
> > + int err = 0;
> > +
> > + ctx = kernel_context(i915);
> > + if (!ctx)
> > + return -ENOMEM;
> > +
> > + scratch = create_scratch(siblings[0]->gt);
> > + if (IS_ERR(scratch)) {
> > + err = PTR_ERR(scratch);
> > + goto out_close;
> > + }
> > +
> > + ve = intel_execlists_create_virtual(ctx, siblings, nsibling);
> > + if (IS_ERR(ve)) {
> > + err = PTR_ERR(ve);
> > + goto out_scratch;
> > + }
> > +
> > + err = intel_context_pin(ve);
> > + if (err)
> > + goto out_put;
> > +
> > + err = igt_live_test_begin(&t, i915, __func__, ve->engine->name);
> > + if (err)
> > + goto out_unpin;
> > +
> > + for (n = 0; n < num_gpr; n++) {
> > + struct intel_engine_cs *engine = siblings[n % nsibling];
> > + struct i915_request *rq;
> > + u32 *cs;
> > +
> > + rq = i915_request_create(ve);
> > + if (IS_ERR(rq)) {
> > + err = PTR_ERR(rq);
> > + goto out_end;
> > + }
> > +
> > + i915_request_put(last);
> > + last = i915_request_get(rq);
> > +
> > + cs = intel_ring_begin(rq, 8);
> > + if (IS_ERR(cs)) {
> > + i915_request_add(rq);
> > + err = PTR_ERR(cs);
> > + goto out_end;
> > + }
> > +
> > + *cs++ = MI_STORE_REGISTER_MEM_GEN8 | MI_USE_GGTT;
> > + *cs++ = CS_GPR(engine, n);
> > + *cs++ = i915_ggtt_offset(scratch) + n * sizeof(u32);
> > + *cs++ = 0;
> > +
> > + *cs++ = MI_LOAD_REGISTER_IMM(1);
> > + *cs++ = CS_GPR(engine, (n + 1) % num_gpr);
> > + *cs++ = n + 1;
> > +
> > + *cs++ = MI_NOOP;
> > + intel_ring_advance(rq, cs);
> > +
> > + /* Restrict this request to run on a particular engine */
> > + rq->execution_mask = engine->mask;
> > + i915_request_add(rq);
> > + }
> > +
> > + if (i915_request_wait(last, 0, HZ / 5) < 0) {
> > + err = -ETIME;
> > + } else {
> > + u32 *map = i915_gem_object_pin_map(scratch->obj, I915_MAP_WB);
> > +
> > + for (n = 0; n < num_gpr; n++) {
> > + if (map[n] != n) {
> > + pr_err("Incorrect value[%d] found for GPR[%d]\n",
> > + map[n], n);
> > + err = -EINVAL;
> > + break;
> > + }
> > + }
> > +
> > + i915_gem_object_unpin_map(scratch->obj);
> > + }
> > +
> > +out_end:
> > + if (igt_live_test_end(&t))
> > + err = -EIO;
> > + i915_request_put(last);
> > +out_unpin:
> > + intel_context_unpin(ve);
> > +out_put:
> > + intel_context_put(ve);
> > +out_scratch:
> > + i915_vma_unpin_and_release(&scratch, 0);
> > +out_close:
> > + kernel_context_close(ctx);
> > + return err;
> > +
> > +#undef CS_GPR
> > +}
> > +
> > +static int live_virtual_preserved(void *arg)
> > +{
> > + struct drm_i915_private *i915 = arg;
> > + struct intel_engine_cs *siblings[MAX_ENGINE_INSTANCE + 1];
> > + struct intel_gt *gt = &i915->gt;
> > + unsigned int class, inst;
> > +
> > + /*
> > + * Check that the context image retains non-privileged (user) registers
> > + * from one engine to the next. For this we check that the CS_GPR
> > + * are preserved.
> > + */
> > +
> > + if (USES_GUC_SUBMISSION(i915))
> > + return 0;
> > +
> > + /* As we use CS_GPR we cannot run before they existed on all engines. */
> > + if (INTEL_GEN(i915) < 9)
> > + return 0;
> > +
> > + for (class = 0; class <= MAX_ENGINE_CLASS; class++) {
> > + int nsibling, err;
> > +
> > + nsibling = 0;
> > + for (inst = 0; inst <= MAX_ENGINE_INSTANCE; inst++) {
> > + if (!gt->engine_class[class][inst])
> > + continue;
> > +
> > + siblings[nsibling++] = gt->engine_class[class][inst];
> > + }
> > + if (nsibling < 2)
> > + continue;
> > +
> > + err = preserved_virtual_engine(i915, siblings, nsibling);
> > + if (err)
> > + return err;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > static int bond_virtual_engine(struct drm_i915_private *i915,
> > unsigned int class,
> > struct intel_engine_cs **siblings,
> > @@ -2277,6 +2456,7 @@ int intel_execlists_live_selftests(struct drm_i915_private *i915)
> > SUBTEST(live_preempt_smoke),
> > SUBTEST(live_virtual_engine),
> > SUBTEST(live_virtual_mask),
> > + SUBTEST(live_virtual_preserved),
> > SUBTEST(live_virtual_bond),
> > };
> >
> >
>
> Looks okay.
>
> CS_GPR0 is tested for zero and never written to which I hope can be
> relied upon. In the docs I did not see it is guaranteed but maybe I
> missed something. And last write of n + 1 is never read-back as well.
Yeah, I'm imposing our guarantee that we don't leak information to
userspace so non-privileged registers are clear for new contexts.
(Give or take those registers that have actual meaning like cache
control.) Hmm, I thought I had checked they start as zero in
igt/gem_ctx_isolation. Appears I was just thinking I had.
-Chris
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