[v6,08/19] drm/i915/gen8: Add 4 level switching infrastructure and lrc support
diff mbox

Message ID 1438187043-34267-9-git-send-email-michel.thierry@intel.com
State New
Headers show

Commit Message

Michel Thierry July 29, 2015, 4:23 p.m. UTC
In 64b (48bit canonical) PPGTT addressing, the PDP0 register contains
the base address to PML4, while the other PDP registers are ignored.

In LRC, the addressing mode must be specified in every context
descriptor, and the base address to PML4 is stored in the reg state.

v2: PML4 update in legacy context switch is left for historic reasons,
the preferred mode of operation is with lrc context based submission.
v3: s/gen8_map_page_directory/gen8_setup_page_directory and
s/gen8_map_page_directory_pointer/gen8_setup_page_directory_pointer.
Also, clflush will be needed for bxt. (Akash)
v4: Squashed lrc-specific code and use a macro to set PML4 register.
v5: Rebase after Mika's ppgtt cleanup / scratch merge patch series.
PDP update in bb_start is only for legacy 32b mode.
v6: Rebase after final merged version of Mika's ppgtt/scratch
patches.
v7: There is no need to update the pml4 register value in
execlists_update_context. (Akash)
v8: Move pd and pdp setup functions to a previous patch, they do not
belong here. (Akash)

Cc: Akash Goel <akash.goel@intel.com>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Michel Thierry <michel.thierry@intel.com> (v2+)
---
 drivers/gpu/drm/i915/i915_gem_gtt.c | 17 +++++++----
 drivers/gpu/drm/i915/i915_reg.h     |  1 +
 drivers/gpu/drm/i915/intel_lrc.c    | 60 ++++++++++++++++++++++++++-----------
 3 files changed, 55 insertions(+), 23 deletions(-)

Comments

akash.goel@intel.com July 30, 2015, 4:14 a.m. UTC | #1
On 7/29/2015 9:53 PM, Michel Thierry wrote:
> In 64b (48bit canonical) PPGTT addressing, the PDP0 register contains
> the base address to PML4, while the other PDP registers are ignored.
>
> In LRC, the addressing mode must be specified in every context
> descriptor, and the base address to PML4 is stored in the reg state.
>
> v2: PML4 update in legacy context switch is left for historic reasons,
> the preferred mode of operation is with lrc context based submission.
> v3: s/gen8_map_page_directory/gen8_setup_page_directory and
> s/gen8_map_page_directory_pointer/gen8_setup_page_directory_pointer.
> Also, clflush will be needed for bxt. (Akash)
> v4: Squashed lrc-specific code and use a macro to set PML4 register.
> v5: Rebase after Mika's ppgtt cleanup / scratch merge patch series.
> PDP update in bb_start is only for legacy 32b mode.
> v6: Rebase after final merged version of Mika's ppgtt/scratch
> patches.
> v7: There is no need to update the pml4 register value in
> execlists_update_context. (Akash)
> v8: Move pd and pdp setup functions to a previous patch, they do not
> belong here. (Akash)
>
> Cc: Akash Goel <akash.goel@intel.com>
> Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> Signed-off-by: Michel Thierry <michel.thierry@intel.com> (v2+)
> ---
>   drivers/gpu/drm/i915/i915_gem_gtt.c | 17 +++++++----
>   drivers/gpu/drm/i915/i915_reg.h     |  1 +
>   drivers/gpu/drm/i915/intel_lrc.c    | 60 ++++++++++++++++++++++++++-----------
>   3 files changed, 55 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> index 4179b80..c6c8af7 100644
> --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> @@ -656,8 +656,8 @@ static int gen8_write_pdp(struct drm_i915_gem_request *req,
>   	return 0;
>   }
>
> -static int gen8_mm_switch(struct i915_hw_ppgtt *ppgtt,
> -			  struct drm_i915_gem_request *req)
> +static int gen8_legacy_mm_switch(struct i915_hw_ppgtt *ppgtt,
> +				 struct drm_i915_gem_request *req)
>   {
>   	int i, ret;
>
> @@ -672,6 +672,12 @@ static int gen8_mm_switch(struct i915_hw_ppgtt *ppgtt,
>   	return 0;
>   }
>
> +static int gen8_48b_mm_switch(struct i915_hw_ppgtt *ppgtt,
> +			      struct drm_i915_gem_request *req)
> +{
> +	return gen8_write_pdp(req, 0, px_dma(&ppgtt->pml4));
> +}
> +
>   static void gen8_ppgtt_clear_pte_range(struct i915_address_space *vm,
>   				       struct i915_page_directory_pointer *pdp,
>   				       uint64_t start,
> @@ -1318,14 +1324,13 @@ static int gen8_ppgtt_init(struct i915_hw_ppgtt *ppgtt)
>   	ppgtt->base.unbind_vma = ppgtt_unbind_vma;
>   	ppgtt->base.bind_vma = ppgtt_bind_vma;
>
> -	ppgtt->switch_mm = gen8_mm_switch;
> -
>   	if (USES_FULL_48BIT_PPGTT(ppgtt->base.dev)) {
>   		ret = setup_px(ppgtt->base.dev, &ppgtt->pml4);
>   		if (ret)
>   			goto free_scratch;
>
>   		ppgtt->base.total = 1ULL << 48;
> +		ppgtt->switch_mm = gen8_48b_mm_switch;
>   	} else {
>   		ret = __pdp_init(false, &ppgtt->pdp);
>   		if (ret)
> @@ -1340,6 +1345,7 @@ static int gen8_ppgtt_init(struct i915_hw_ppgtt *ppgtt)
>   			 */
>   			ppgtt->base.total = to_i915(ppgtt->base.dev)->gtt.base.total;
>
> +		ppgtt->switch_mm = gen8_legacy_mm_switch;
>   		trace_i915_page_directory_pointer_entry_alloc(&ppgtt->base,
>   							      0, 0,
>   							      GEN8_PML4E_SHIFT);
> @@ -1537,8 +1543,9 @@ static void gen8_ppgtt_enable(struct drm_device *dev)
>   	int j;
>
>   	for_each_ring(ring, dev_priv, j) {
> +		u32 four_level = USES_FULL_48BIT_PPGTT(dev) ? GEN8_GFX_PPGTT_48B : 0;
>   		I915_WRITE(RING_MODE_GEN7(ring),
> -			   _MASKED_BIT_ENABLE(GFX_PPGTT_ENABLE));
> +			   _MASKED_BIT_ENABLE(GFX_PPGTT_ENABLE | four_level));
>   	}
>   }
>
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 3a77678..5bd1b6a 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -1670,6 +1670,7 @@ enum skl_disp_power_wells {
>   #define   GFX_REPLAY_MODE		(1<<11)
>   #define   GFX_PSMI_GRANULARITY		(1<<10)
>   #define   GFX_PPGTT_ENABLE		(1<<9)
> +#define   GEN8_GFX_PPGTT_48B		(1<<7)
>
>   #define VLV_DISPLAY_BASE 0x180000
>   #define VLV_MIPI_BASE VLV_DISPLAY_BASE
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index 99bba8e..0b65188 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -196,13 +196,21 @@
>   	reg_state[CTX_PDP ## n ## _LDW+1] = lower_32_bits(_addr); \
>   }
>
> +#define ASSIGN_CTX_PML4(ppgtt, reg_state) { \
> +	reg_state[CTX_PDP0_UDW + 1] = upper_32_bits(px_dma(&ppgtt->pml4)); \
> +	reg_state[CTX_PDP0_LDW + 1] = lower_32_bits(px_dma(&ppgtt->pml4)); \
> +}
> +
>   enum {
>   	ADVANCED_CONTEXT = 0,
> -	LEGACY_CONTEXT,
> +	LEGACY_32B_CONTEXT,
>   	ADVANCED_AD_CONTEXT,
>   	LEGACY_64B_CONTEXT
>   };
> -#define GEN8_CTX_MODE_SHIFT 3
> +#define GEN8_CTX_ADDRESSING_MODE_SHIFT 3
> +#define GEN8_CTX_ADDRESSING_MODE(dev)  (USES_FULL_48BIT_PPGTT(dev) ?\
> +		LEGACY_64B_CONTEXT :\
> +		LEGACY_32B_CONTEXT)
>   enum {
>   	FAULT_AND_HANG = 0,
>   	FAULT_AND_HALT, /* Debug only */
> @@ -273,7 +281,7 @@ static uint64_t execlists_ctx_descriptor(struct drm_i915_gem_request *rq)
>   	WARN_ON(lrca & 0xFFFFFFFF00000FFFULL);
>
>   	desc = GEN8_CTX_VALID;
> -	desc |= LEGACY_CONTEXT << GEN8_CTX_MODE_SHIFT;
> +	desc |= GEN8_CTX_ADDRESSING_MODE(dev) << GEN8_CTX_ADDRESSING_MODE_SHIFT;
>   	if (IS_GEN8(ctx_obj->base.dev))
>   		desc |= GEN8_CTX_L3LLC_COHERENT;
>   	desc |= GEN8_CTX_PRIVILEGE;
> @@ -348,10 +356,12 @@ static int execlists_update_context(struct drm_i915_gem_request *rq)
>   	reg_state[CTX_RING_TAIL+1] = rq->tail;
>   	reg_state[CTX_RING_BUFFER_START+1] = i915_gem_obj_ggtt_offset(rb_obj);
>
> -	/* True PPGTT with dynamic page allocation: update PDP registers and
> -	 * point the unallocated PDPs to the scratch page
> -	 */
> -	if (ppgtt) {
> +	if (ppgtt && !USES_FULL_48BIT_PPGTT(ppgtt->base.dev)) {
> +		/* True 32b PPGTT with dynamic page allocation: update PDP
> +		 * registers and point the unallocated PDPs to scratch page.
> +		 * PML4 is allocated during ppgtt init, so this is not needed
> +		 * in 48-bit mode.
> +		 */
>   		ASSIGN_CTX_PDP(ppgtt, reg_state, 3);
>   		ASSIGN_CTX_PDP(ppgtt, reg_state, 2);
>   		ASSIGN_CTX_PDP(ppgtt, reg_state, 1);
> @@ -1512,12 +1522,15 @@ static int gen8_emit_bb_start(struct drm_i915_gem_request *req,
>   	 * Ideally, we should set Force PD Restore in ctx descriptor,
>   	 * but we can't. Force Restore would be a second option, but
>   	 * it is unsafe in case of lite-restore (because the ctx is
> -	 * not idle). */
> +	 * not idle). PML4 is allocated during ppgtt init so this is
> +	 * not needed in 48-bit.*/
>   	if (req->ctx->ppgtt &&
>   	    (intel_ring_flag(req->ring) & req->ctx->ppgtt->pd_dirty_rings)) {
> -		ret = intel_logical_ring_emit_pdps(req);
> -		if (ret)
> -			return ret;
> +		if (GEN8_CTX_ADDRESSING_MODE(req->i915) == LEGACY_32B_CONTEXT) {
Sorry for the late comment.
For consistency, better to use 'USES_FULL_48BIT_PPGTT' macro only here, 
as that will also imply the same thing i.e. which type of Context 
addressing mode is being used.

Best regards
Akash

> +			ret = intel_logical_ring_emit_pdps(req);
> +			if (ret)
> +				return ret;
> +		}
>
>   		req->ctx->ppgtt->pd_dirty_rings &= ~intel_ring_flag(req->ring);
>   	}
> @@ -2198,13 +2211,24 @@ populate_lr_context(struct intel_context *ctx, struct drm_i915_gem_object *ctx_o
>   	reg_state[CTX_PDP0_UDW] = GEN8_RING_PDP_UDW(ring, 0);
>   	reg_state[CTX_PDP0_LDW] = GEN8_RING_PDP_LDW(ring, 0);
>
> -	/* With dynamic page allocation, PDPs may not be allocated at this point,
> -	 * Point the unallocated PDPs to the scratch page
> -	 */
> -	ASSIGN_CTX_PDP(ppgtt, reg_state, 3);
> -	ASSIGN_CTX_PDP(ppgtt, reg_state, 2);
> -	ASSIGN_CTX_PDP(ppgtt, reg_state, 1);
> -	ASSIGN_CTX_PDP(ppgtt, reg_state, 0);
> +	if (USES_FULL_48BIT_PPGTT(ppgtt->base.dev)) {
> +		/* 64b PPGTT (48bit canonical)
> +		 * PDP0_DESCRIPTOR contains the base address to PML4 and
> +		 * other PDP Descriptors are ignored.
> +		 */
> +		ASSIGN_CTX_PML4(ppgtt, reg_state);
> +	} else {
> +		/* 32b PPGTT
> +		 * PDP*_DESCRIPTOR contains the base address of space supported.
> +		 * With dynamic page allocation, PDPs may not be allocated at
> +		 * this point. Point the unallocated PDPs to the scratch page
> +		 */
> +		ASSIGN_CTX_PDP(ppgtt, reg_state, 3);
> +		ASSIGN_CTX_PDP(ppgtt, reg_state, 2);
> +		ASSIGN_CTX_PDP(ppgtt, reg_state, 1);
> +		ASSIGN_CTX_PDP(ppgtt, reg_state, 0);
> +	}
> +
>   	if (ring->id == RCS) {
>   		reg_state[CTX_LRI_HEADER_2] = MI_LOAD_REGISTER_IMM(1);
>   		reg_state[CTX_R_PWR_CLK_STATE] = GEN8_R_PWR_CLK_STATE;
>
Michel Thierry July 30, 2015, 9:36 a.m. UTC | #2
On 7/30/2015 5:14 AM, Goel, Akash wrote:
> On 7/29/2015 9:53 PM, Michel Thierry wrote:
>> @@ -1512,12 +1522,15 @@ static int gen8_emit_bb_start(struct
>> drm_i915_gem_request *req,
>>        * Ideally, we should set Force PD Restore in ctx descriptor,
>>        * but we can't. Force Restore would be a second option, but
>>        * it is unsafe in case of lite-restore (because the ctx is
>> -     * not idle). */
>> +     * not idle). PML4 is allocated during ppgtt init so this is
>> +     * not needed in 48-bit.*/
>>       if (req->ctx->ppgtt &&
>>           (intel_ring_flag(req->ring) &
>> req->ctx->ppgtt->pd_dirty_rings)) {
>> -        ret = intel_logical_ring_emit_pdps(req);
>> -        if (ret)
>> -            return ret;
>> +        if (GEN8_CTX_ADDRESSING_MODE(req->i915) == LEGACY_32B_CONTEXT) {
> Sorry for the late comment.
> For consistency, better to use 'USES_FULL_48BIT_PPGTT' macro only here,
> as that will also imply the same thing i.e. which type of Context
> addressing mode is being used.
>
> Best regards
> Akash
>

Ack. I'm changing it to  if (!USES_FULL_48BIT_PPGTT(req->i915)).

Patch
diff mbox

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 4179b80..c6c8af7 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -656,8 +656,8 @@  static int gen8_write_pdp(struct drm_i915_gem_request *req,
 	return 0;
 }
 
-static int gen8_mm_switch(struct i915_hw_ppgtt *ppgtt,
-			  struct drm_i915_gem_request *req)
+static int gen8_legacy_mm_switch(struct i915_hw_ppgtt *ppgtt,
+				 struct drm_i915_gem_request *req)
 {
 	int i, ret;
 
@@ -672,6 +672,12 @@  static int gen8_mm_switch(struct i915_hw_ppgtt *ppgtt,
 	return 0;
 }
 
+static int gen8_48b_mm_switch(struct i915_hw_ppgtt *ppgtt,
+			      struct drm_i915_gem_request *req)
+{
+	return gen8_write_pdp(req, 0, px_dma(&ppgtt->pml4));
+}
+
 static void gen8_ppgtt_clear_pte_range(struct i915_address_space *vm,
 				       struct i915_page_directory_pointer *pdp,
 				       uint64_t start,
@@ -1318,14 +1324,13 @@  static int gen8_ppgtt_init(struct i915_hw_ppgtt *ppgtt)
 	ppgtt->base.unbind_vma = ppgtt_unbind_vma;
 	ppgtt->base.bind_vma = ppgtt_bind_vma;
 
-	ppgtt->switch_mm = gen8_mm_switch;
-
 	if (USES_FULL_48BIT_PPGTT(ppgtt->base.dev)) {
 		ret = setup_px(ppgtt->base.dev, &ppgtt->pml4);
 		if (ret)
 			goto free_scratch;
 
 		ppgtt->base.total = 1ULL << 48;
+		ppgtt->switch_mm = gen8_48b_mm_switch;
 	} else {
 		ret = __pdp_init(false, &ppgtt->pdp);
 		if (ret)
@@ -1340,6 +1345,7 @@  static int gen8_ppgtt_init(struct i915_hw_ppgtt *ppgtt)
 			 */
 			ppgtt->base.total = to_i915(ppgtt->base.dev)->gtt.base.total;
 
+		ppgtt->switch_mm = gen8_legacy_mm_switch;
 		trace_i915_page_directory_pointer_entry_alloc(&ppgtt->base,
 							      0, 0,
 							      GEN8_PML4E_SHIFT);
@@ -1537,8 +1543,9 @@  static void gen8_ppgtt_enable(struct drm_device *dev)
 	int j;
 
 	for_each_ring(ring, dev_priv, j) {
+		u32 four_level = USES_FULL_48BIT_PPGTT(dev) ? GEN8_GFX_PPGTT_48B : 0;
 		I915_WRITE(RING_MODE_GEN7(ring),
-			   _MASKED_BIT_ENABLE(GFX_PPGTT_ENABLE));
+			   _MASKED_BIT_ENABLE(GFX_PPGTT_ENABLE | four_level));
 	}
 }
 
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 3a77678..5bd1b6a 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -1670,6 +1670,7 @@  enum skl_disp_power_wells {
 #define   GFX_REPLAY_MODE		(1<<11)
 #define   GFX_PSMI_GRANULARITY		(1<<10)
 #define   GFX_PPGTT_ENABLE		(1<<9)
+#define   GEN8_GFX_PPGTT_48B		(1<<7)
 
 #define VLV_DISPLAY_BASE 0x180000
 #define VLV_MIPI_BASE VLV_DISPLAY_BASE
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 99bba8e..0b65188 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -196,13 +196,21 @@ 
 	reg_state[CTX_PDP ## n ## _LDW+1] = lower_32_bits(_addr); \
 }
 
+#define ASSIGN_CTX_PML4(ppgtt, reg_state) { \
+	reg_state[CTX_PDP0_UDW + 1] = upper_32_bits(px_dma(&ppgtt->pml4)); \
+	reg_state[CTX_PDP0_LDW + 1] = lower_32_bits(px_dma(&ppgtt->pml4)); \
+}
+
 enum {
 	ADVANCED_CONTEXT = 0,
-	LEGACY_CONTEXT,
+	LEGACY_32B_CONTEXT,
 	ADVANCED_AD_CONTEXT,
 	LEGACY_64B_CONTEXT
 };
-#define GEN8_CTX_MODE_SHIFT 3
+#define GEN8_CTX_ADDRESSING_MODE_SHIFT 3
+#define GEN8_CTX_ADDRESSING_MODE(dev)  (USES_FULL_48BIT_PPGTT(dev) ?\
+		LEGACY_64B_CONTEXT :\
+		LEGACY_32B_CONTEXT)
 enum {
 	FAULT_AND_HANG = 0,
 	FAULT_AND_HALT, /* Debug only */
@@ -273,7 +281,7 @@  static uint64_t execlists_ctx_descriptor(struct drm_i915_gem_request *rq)
 	WARN_ON(lrca & 0xFFFFFFFF00000FFFULL);
 
 	desc = GEN8_CTX_VALID;
-	desc |= LEGACY_CONTEXT << GEN8_CTX_MODE_SHIFT;
+	desc |= GEN8_CTX_ADDRESSING_MODE(dev) << GEN8_CTX_ADDRESSING_MODE_SHIFT;
 	if (IS_GEN8(ctx_obj->base.dev))
 		desc |= GEN8_CTX_L3LLC_COHERENT;
 	desc |= GEN8_CTX_PRIVILEGE;
@@ -348,10 +356,12 @@  static int execlists_update_context(struct drm_i915_gem_request *rq)
 	reg_state[CTX_RING_TAIL+1] = rq->tail;
 	reg_state[CTX_RING_BUFFER_START+1] = i915_gem_obj_ggtt_offset(rb_obj);
 
-	/* True PPGTT with dynamic page allocation: update PDP registers and
-	 * point the unallocated PDPs to the scratch page
-	 */
-	if (ppgtt) {
+	if (ppgtt && !USES_FULL_48BIT_PPGTT(ppgtt->base.dev)) {
+		/* True 32b PPGTT with dynamic page allocation: update PDP
+		 * registers and point the unallocated PDPs to scratch page.
+		 * PML4 is allocated during ppgtt init, so this is not needed
+		 * in 48-bit mode.
+		 */
 		ASSIGN_CTX_PDP(ppgtt, reg_state, 3);
 		ASSIGN_CTX_PDP(ppgtt, reg_state, 2);
 		ASSIGN_CTX_PDP(ppgtt, reg_state, 1);
@@ -1512,12 +1522,15 @@  static int gen8_emit_bb_start(struct drm_i915_gem_request *req,
 	 * Ideally, we should set Force PD Restore in ctx descriptor,
 	 * but we can't. Force Restore would be a second option, but
 	 * it is unsafe in case of lite-restore (because the ctx is
-	 * not idle). */
+	 * not idle). PML4 is allocated during ppgtt init so this is
+	 * not needed in 48-bit.*/
 	if (req->ctx->ppgtt &&
 	    (intel_ring_flag(req->ring) & req->ctx->ppgtt->pd_dirty_rings)) {
-		ret = intel_logical_ring_emit_pdps(req);
-		if (ret)
-			return ret;
+		if (GEN8_CTX_ADDRESSING_MODE(req->i915) == LEGACY_32B_CONTEXT) {
+			ret = intel_logical_ring_emit_pdps(req);
+			if (ret)
+				return ret;
+		}
 
 		req->ctx->ppgtt->pd_dirty_rings &= ~intel_ring_flag(req->ring);
 	}
@@ -2198,13 +2211,24 @@  populate_lr_context(struct intel_context *ctx, struct drm_i915_gem_object *ctx_o
 	reg_state[CTX_PDP0_UDW] = GEN8_RING_PDP_UDW(ring, 0);
 	reg_state[CTX_PDP0_LDW] = GEN8_RING_PDP_LDW(ring, 0);
 
-	/* With dynamic page allocation, PDPs may not be allocated at this point,
-	 * Point the unallocated PDPs to the scratch page
-	 */
-	ASSIGN_CTX_PDP(ppgtt, reg_state, 3);
-	ASSIGN_CTX_PDP(ppgtt, reg_state, 2);
-	ASSIGN_CTX_PDP(ppgtt, reg_state, 1);
-	ASSIGN_CTX_PDP(ppgtt, reg_state, 0);
+	if (USES_FULL_48BIT_PPGTT(ppgtt->base.dev)) {
+		/* 64b PPGTT (48bit canonical)
+		 * PDP0_DESCRIPTOR contains the base address to PML4 and
+		 * other PDP Descriptors are ignored.
+		 */
+		ASSIGN_CTX_PML4(ppgtt, reg_state);
+	} else {
+		/* 32b PPGTT
+		 * PDP*_DESCRIPTOR contains the base address of space supported.
+		 * With dynamic page allocation, PDPs may not be allocated at
+		 * this point. Point the unallocated PDPs to the scratch page
+		 */
+		ASSIGN_CTX_PDP(ppgtt, reg_state, 3);
+		ASSIGN_CTX_PDP(ppgtt, reg_state, 2);
+		ASSIGN_CTX_PDP(ppgtt, reg_state, 1);
+		ASSIGN_CTX_PDP(ppgtt, reg_state, 0);
+	}
+
 	if (ring->id == RCS) {
 		reg_state[CTX_LRI_HEADER_2] = MI_LOAD_REGISTER_IMM(1);
 		reg_state[CTX_R_PWR_CLK_STATE] = GEN8_R_PWR_CLK_STATE;