drm/i915/gen7: Re-enable full-ppgtt for ivb & hsw

After much hair pulling, resort to preallocating the ppGTT entries on
init to circumvent the apparent lack of PD invalidate following the
write to PP_DCLV upon switching mm between contexts (and here the same
context after binding new objects). However, the details of that PP_DCLV
invalidate are still unknown, and it appears we need to reload the mm
twice to cover over a timing issue. Worrying.

Fixes: 3dc007fe9b ("drm/i915/gtt: Downgrade gen7 (ivb, byt, hsw) back to aliasing-ppgtt")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191129201328.1398583-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gt/intel_ring_submission.c

@@ -1366,7 +1366,7 @@ static int load_pd_dir(struct i915_request *rq, const struct i915_ppgtt *ppgtt)
 	const struct intel_engine_cs * const engine = rq->engine;
 	u32 *cs;
 
-	cs = intel_ring_begin(rq, 6);
+	cs = intel_ring_begin(rq, 10);
 	if (IS_ERR(cs))
 		return PTR_ERR(cs);
 
@@ -1374,6 +1374,12 @@ static int load_pd_dir(struct i915_request *rq, const struct i915_ppgtt *ppgtt)
 	*cs++ = i915_mmio_reg_offset(RING_PP_DIR_DCLV(engine->mmio_base));
 	*cs++ = PP_DIR_DCLV_2G;
 
+	*cs++ = MI_STORE_REGISTER_MEM | MI_SRM_LRM_GLOBAL_GTT;
+	*cs++ = i915_mmio_reg_offset(RING_PP_DIR_DCLV(engine->mmio_base));
+	*cs++ = intel_gt_scratch_offset(rq->engine->gt,
+					INTEL_GT_SCRATCH_FIELD_DEFAULT);
+	*cs++ = MI_NOOP;
+
 	*cs++ = MI_LOAD_REGISTER_IMM(1);
 	*cs++ = i915_mmio_reg_offset(RING_PP_DIR_BASE(engine->mmio_base));
 	*cs++ = px_base(ppgtt->pd)->ggtt_offset << 10;
@@ -1579,6 +1585,7 @@ static int switch_context(struct i915_request *rq)
 {
 	struct intel_context *ce = rq->hw_context;
 	struct i915_address_space *vm = vm_alias(ce);
+	u32 hw_flags = 0;
 	int ret;
 
 	GEM_BUG_ON(HAS_EXECLISTS(rq->i915));
@@ -1590,19 +1597,9 @@ static int switch_context(struct i915_request *rq)
 	}
 
 	if (ce->state) {
-		u32 hw_flags;
-
 		GEM_BUG_ON(rq->engine->id != RCS0);
 
-		/*
-		 * The kernel context(s) is treated as pure scratch and is not
-		 * expected to retain any state (as we sacrifice it during
-		 * suspend and on resume it may be corrupted). This is ok,
-		 * as nothing actually executes using the kernel context; it
-		 * is purely used for flushing user contexts.
-		 */
-		hw_flags = 0;
-		if (i915_gem_context_is_kernel(rq->gem_context))
+		if (!rq->engine->default_state)
 			hw_flags = MI_RESTORE_INHIBIT;
 
 		ret = mi_set_context(rq, hw_flags);

drivers/gpu/drm/i915/i915_gem_gtt.c

@@ -1692,7 +1692,6 @@ static int gen6_alloc_va_range(struct i915_address_space *vm,
 	intel_wakeref_t wakeref;
 	u64 from = start;
 	unsigned int pde;
-	bool flush = false;
 	int ret = 0;
 
 	wakeref = intel_runtime_pm_get(&vm->i915->runtime_pm);
@@ -1717,11 +1716,6 @@ static int gen6_alloc_va_range(struct i915_address_space *vm,
 			spin_lock(&pd->lock);
 			if (pd->entry[pde] == &vm->scratch[1]) {
 				pd->entry[pde] = pt;
-				if (i915_vma_is_bound(ppgtt->vma,
-						      I915_VMA_GLOBAL_BIND)) {
-					gen6_write_pde(ppgtt, pde, pt);
-					flush = true;
-				}
 			} else {
 				alloc = pt;
 				pt = pd->entry[pde];
@@ -1732,9 +1726,19 @@ static int gen6_alloc_va_range(struct i915_address_space *vm,
 	}
 	spin_unlock(&pd->lock);
 
-	if (flush)
+	if (i915_vma_is_bound(ppgtt->vma, I915_VMA_GLOBAL_BIND)) {
+		mutex_lock(&ppgtt->flush);
+
+		/* Rewrite them all! Anything less misses an invalidate. */
+		gen6_for_all_pdes(pt, pd, pde)
+			gen6_write_pde(ppgtt, pde, pt);
+
+		ioread32(ppgtt->pd_addr + pde - 1);
 		gen6_ggtt_invalidate(vm->gt->ggtt);
 
+		mutex_unlock(&ppgtt->flush);
+	}
+
 	goto out;
 
 unwind_out:
@@ -1793,6 +1797,7 @@ static void gen6_ppgtt_cleanup(struct i915_address_space *vm)
 	gen6_ppgtt_free_pd(ppgtt);
 	free_scratch(vm);
 
+	mutex_destroy(&ppgtt->flush);
 	mutex_destroy(&ppgtt->pin_mutex);
 	kfree(ppgtt->base.pd);
 }
@@ -1958,6 +1963,7 @@ static struct i915_ppgtt *gen6_ppgtt_create(struct drm_i915_private *i915)
 	if (!ppgtt)
 		return ERR_PTR(-ENOMEM);
 
+	mutex_init(&ppgtt->flush);
 	mutex_init(&ppgtt->pin_mutex);
 
 	ppgtt_init(&ppgtt->base, &i915->gt);
@@ -1994,6 +2000,7 @@ err_scratch:
 err_pd:
 	kfree(ppgtt->base.pd);
 err_free:
+	mutex_destroy(&ppgtt->pin_mutex);
 	kfree(ppgtt);
 	return ERR_PTR(err);
 }

drivers/gpu/drm/i915/i915_gem_gtt.h

@@ -443,6 +443,7 @@ struct i915_ppgtt {
 struct gen6_ppgtt {
 	struct i915_ppgtt base;
 
+	struct mutex flush;
 	struct i915_vma *vma;
 	gen6_pte_t __iomem *pd_addr;
 

drivers/gpu/drm/i915/i915_pci.c

@@ -436,7 +436,7 @@ static const struct intel_device_info intel_sandybridge_m_gt2_info = {
 	.has_rc6 = 1, \
 	.has_rc6p = 1, \
 	.has_rps = true, \
-	.ppgtt_type = INTEL_PPGTT_ALIASING, \
+	.ppgtt_type = INTEL_PPGTT_FULL, \
 	.ppgtt_size = 31, \
 	IVB_PIPE_OFFSETS, \
 	IVB_CURSOR_OFFSETS, \