[Intel-gfx] [PATCH v12 1/4] drm/i915: Enable NULL PTE support for vm scratch

[Jonathan Cavitt]

Enable NULL PTE support for vm scratch pages.

The use of NULL PTEs in teh vm scratch pages requires us to change how
the i915 gem_contexts live selftest perform vm_isolation: instead of
checking the scratch pages are isolated and don't affect each other, we
check that all changes to the scratch pages are voided.

Signed-off-by: Jonathan Cavitt <jonathan.cavitt at intel.com>
Suggested-by: Chris Wilson <chris.p.wilson at linux.intel.com>
---
 drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c | 6 ++++++
 drivers/gpu/drm/i915/gt/gen8_ppgtt.c                  | 3 +++
 drivers/gpu/drm/i915/gt/intel_gtt.h                   | 1 +
 drivers/gpu/drm/i915/i915_drv.h                       | 2 ++
 drivers/gpu/drm/i915/i915_pci.c                       | 2 ++
 drivers/gpu/drm/i915/intel_device_info.h              | 1 +
 6 files changed, 15 insertions(+)

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 7021b6e9b219e..48fc5990343bc 100644
--- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
@@ -1751,6 +1751,12 @@ static int check_scratch_page(struct i915_gem_context *ctx, u32 *out)
 	if (!vm)
 		return -ENODEV;
 
+	if (HAS_NULL_PAGE(vm->i915)) {
+		if (out)
+			*out = 0;
+		return 0;
+	}
+
 	if (!vm->scratch[0]) {
 		pr_err("No scratch page!\n");
 		return -EINVAL;
diff --git a/drivers/gpu/drm/i915/gt/gen8_ppgtt.c b/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
index 9895e18df0435..84aa29715e0ac 100644
--- a/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
+++ b/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
@@ -855,6 +855,9 @@ static int gen8_init_scratch(struct i915_address_space *vm)
 						      I915_CACHE_NONE),
 			       pte_flags);
 
+	if (HAS_NULL_PAGE(vm->i915))
+		vm->scratch[0]->encode |= PTE_NULL_PAGE;
+
 	for (i = 1; i <= vm->top; i++) {
 		struct drm_i915_gem_object *obj;
 
diff --git a/drivers/gpu/drm/i915/gt/intel_gtt.h b/drivers/gpu/drm/i915/gt/intel_gtt.h
index 346ec8ec2edda..153ddfca0ae18 100644
--- a/drivers/gpu/drm/i915/gt/intel_gtt.h
+++ b/drivers/gpu/drm/i915/gt/intel_gtt.h
@@ -151,6 +151,7 @@ typedef u64 gen8_pte_t;
 
 #define GEN8_PAGE_PRESENT		BIT_ULL(0)
 #define GEN8_PAGE_RW			BIT_ULL(1)
+#define PTE_NULL_PAGE			BIT_ULL(9)
 
 #define GEN8_PDE_IPS_64K BIT(11)
 #define GEN8_PDE_PS_2M   BIT(7)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 87ffc477c3b1a..687a8fcdc3d54 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -782,6 +782,8 @@ IS_SUBPLATFORM(const struct drm_i915_private *i915,
  */
 #define HAS_FLAT_CCS(i915)   (INTEL_INFO(i915)->has_flat_ccs)
 
+#define HAS_NULL_PAGE(dev_priv) (INTEL_INFO(dev_priv)->has_null_page)
+
 #define HAS_GT_UC(i915)	(INTEL_INFO(i915)->has_gt_uc)
 
 #define HAS_POOLED_EU(i915)	(RUNTIME_INFO(i915)->has_pooled_eu)
diff --git a/drivers/gpu/drm/i915/i915_pci.c b/drivers/gpu/drm/i915/i915_pci.c
index df7c261410f79..80a65ea192107 100644
--- a/drivers/gpu/drm/i915/i915_pci.c
+++ b/drivers/gpu/drm/i915/i915_pci.c
@@ -642,6 +642,7 @@ static const struct intel_device_info jsl_info = {
 	GEN(12), \
 	TGL_CACHELEVEL, \
 	.has_global_mocs = 1, \
+	.has_null_page = 1, \
 	.has_pxp = 1, \
 	.max_pat_index = 3
 
@@ -721,6 +722,7 @@ static const struct intel_device_info adl_p_info = {
 	.has_mslice_steering = 1, \
 	.has_oa_bpc_reporting = 1, \
 	.has_oa_slice_contrib_limits = 1, \
+	.has_null_page = 1, \
 	.has_oam = 1, \
 	.has_rc6 = 1, \
 	.has_reset_engine = 1, \
diff --git a/drivers/gpu/drm/i915/intel_device_info.h b/drivers/gpu/drm/i915/intel_device_info.h
index 39817490b13fd..252f8dc0fe790 100644
--- a/drivers/gpu/drm/i915/intel_device_info.h
+++ b/drivers/gpu/drm/i915/intel_device_info.h
@@ -162,6 +162,7 @@ enum intel_ppgtt_type {
 	func(has_mslice_steering); \
 	func(has_oa_bpc_reporting); \
 	func(has_oa_slice_contrib_limits); \
+	func(has_null_page); \
 	func(has_oam); \
 	func(has_one_eu_per_fuse_bit); \
 	func(has_pxp); \
-- 
2.25.1