drm/xe/xe2: Introduce identity map for compressed pat for vram

Xe2+ has unified compression (exactly one compression mode/format),
where compression is now controlled via PAT at PTE level.
This simplifies KMD operations, as it can now decompress freely
without concern for the buffer's original compression format—unlike DG2,
which had multiple compression formats and thus required copying the
raw CCS state during VRAM eviction. In addition mixed VRAM and system
memory buffers were not supported with compression enabled.

On Xe2 dGPU compression is still only supported with VRAM, however we
can now support compression with VRAM and system memory buffers,
with GPU access being seamless underneath. So long as when doing
VRAM -> system memory the KMD uses compressed -> uncompressed,
to decompress it. This also allows CPU access to such buffers,
assuming that userspace first decompress the corresponding
pages being accessed.
If the pages are already in system memory then KMD would have already
decompressed them. When restoring such buffers with sysmem -> VRAM
the KMD can't easily know which pages were originally compressed,
so we always use uncompressed -> uncompressed here.
With this it also means we can drop all the raw CCS handling on such
platforms (including needing to allocate extra CCS storage).

In order to support this we now need to have two different identity
mappings for compressed and uncompressed VRAM.
In this patch, we set up the additional identity map for the VRAM with
compressed pat_index. We then select the appropriate mapping during
migration/clear. During eviction (vram->sysmem), we use the mapping
from compressed -> uncompressed. During restore (sysmem->vram), we need
the mapping from uncompressed -> uncompressed.
Therefore, we need to have two different mappings for compressed and
uncompressed vram. We set up an additional identity map for the vram
with compressed pat_index.
We then select the appropriate mapping during migration/clear.

v2: Formatting nits, Updated code to match recent changes in
xe_migrate_prepare_vm(). (Matt)

v3: Move identity map loop to a helper function. (Matt Brost)

v4: Split helper function in different patch, and
add asserts and nits. (Matt Brost)

v5: Convert the 2 bool arguments of pte_update_size to flags
argument (Matt Brost)

v6: Formatting nits (Matt Brost)

Signed-off-by: Akshata Jahagirdar <[e-mail]>
Reviewed-by: Himal Prasad Ghimiray <[e-mail]>
Reviewed-by: Matthew Brost <[e-mail]>
Signed-off-by: Matt Roper <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/b00db5c726[e-mail]

drivers/gpu/drm/xe/tests/xe_migrate.c

···
 		u32 flush_flags = 0;
 		u32 update_idx;
 		u32 avail_pts = max_mem_transfer_per_pass(xe) / LEVEL0_PAGE_TABLE_ENCODE_SIZE;
+		u32 pte_flags;
 
 		src_L0 = xe_migrate_res_sizes(m, &src_it);
 		dst_L0 = xe_migrate_res_sizes(m, &dst_it);
 
 		src_L0 = min(src_L0, dst_L0);
 
-		batch_size += pte_update_size(m, src_is_vram, src_is_vram, src, &src_it, &src_L0,
+		pte_flags = src_is_vram ? (PTE_UPDATE_FLAG_IS_VRAM |
+					   PTE_UPDATE_FLAG_IS_COMP_PTE) : 0;
+		batch_size += pte_update_size(m, pte_flags, src, &src_it, &src_L0,
 					      &src_L0_ofs, &src_L0_pt, 0, 0,
 					      avail_pts);
 
-		batch_size += pte_update_size(m, dst_is_vram, dst_is_vram, dst, &dst_it, &src_L0,
+		pte_flags = dst_is_vram ? (PTE_UPDATE_FLAG_IS_VRAM |
+					   PTE_UPDATE_FLAG_IS_COMP_PTE) : 0;
+		batch_size += pte_update_size(m, pte_flags, dst, &dst_it, &src_L0,
 					      &dst_L0_ofs, &dst_L0_pt, 0,
 					      avail_pts, avail_pts);
 

drivers/gpu/drm/xe/xe_migrate.c

···
 #define NUM_PT_SLOTS 32
 #define LEVEL0_PAGE_TABLE_ENCODE_SIZE SZ_2M
 #define MAX_NUM_PTE 512
+#define IDENTITY_OFFSET 256ULL
 
 /*
  * Although MI_STORE_DATA_IMM's "length" field is 10-bits, 0x3FE is the largest
···
 	return (slot + 1ULL) << xe_pt_shift(level + 1);
 }
 
-static u64 xe_migrate_vram_ofs(struct xe_device *xe, u64 addr)
+static u64 xe_migrate_vram_ofs(struct xe_device *xe, u64 addr, bool is_comp_pte)
 {
 	/*
 	 * Remove the DPA to get a correct offset into identity table for the
 	 * migrate offset
 	 */
+	u64 identity_offset = IDENTITY_OFFSET;
+
+	if (GRAPHICS_VER(xe) >= 20 && is_comp_pte)
+		identity_offset += DIV_ROUND_UP_ULL(xe->mem.vram.actual_physical_size, SZ_1G);
+
 	addr -= xe->mem.vram.dpa_base;
-	return addr + (256ULL << xe_pt_shift(2));
+	return addr + (identity_offset << xe_pt_shift(2));
 }
 
 static void xe_migrate_program_identity(struct xe_device *xe, struct xe_vm *vm, struct xe_bo *bo,
···
 	struct xe_device *xe = tile_to_xe(tile);
 	u16 pat_index = xe->pat.idx[XE_CACHE_WB];
 	u8 id = tile->id;
-	u32 num_entries = NUM_PT_SLOTS, num_level = vm->pt_root[id]->level,
-	    num_setup = num_level + 1;
+	u32 num_entries = NUM_PT_SLOTS, num_level = vm->pt_root[id]->level;
+#define VRAM_IDENTITY_MAP_COUNT	2
+	u32 num_setup = num_level + VRAM_IDENTITY_MAP_COUNT;
+#undef VRAM_IDENTITY_MAP_COUNT
 	u32 map_ofs, level, i;
 	struct xe_bo *bo, *batch = tile->mem.kernel_bb_pool->bo;
-	u64 entry, pt30_ofs;
+	u64 entry, pt29_ofs;
 
 	/* Can't bump NUM_PT_SLOTS too high */
 	BUILD_BUG_ON(NUM_PT_SLOTS > SZ_2M/XE_PAGE_SIZE);
···
 	if (IS_ERR(bo))
 		return PTR_ERR(bo);
 
-	/* PT31 reserved for 2M identity map */
-	pt30_ofs = bo->size - 2 * XE_PAGE_SIZE;
-	entry = vm->pt_ops->pde_encode_bo(bo, pt30_ofs, pat_index);
+	/* PT30 & PT31 reserved for 2M identity map */
+	pt29_ofs = bo->size - 3 * XE_PAGE_SIZE;
+	entry = vm->pt_ops->pde_encode_bo(bo, pt29_ofs, pat_index);
 	xe_pt_write(xe, &vm->pt_root[id]->bo->vmap, 0, entry);
 
 	map_ofs = (num_entries - num_setup) * XE_PAGE_SIZE;
···
 	} else {
 		u64 batch_addr = xe_bo_addr(batch, 0, XE_PAGE_SIZE);
 
-		m->batch_base_ofs = xe_migrate_vram_ofs(xe, batch_addr);
+		m->batch_base_ofs = xe_migrate_vram_ofs(xe, batch_addr, false);
 
 		if (xe->info.has_usm) {
 			batch = tile->primary_gt->usm.bb_pool->bo;
 			batch_addr = xe_bo_addr(batch, 0, XE_PAGE_SIZE);
-			m->usm_batch_base_ofs = xe_migrate_vram_ofs(xe, batch_addr);
+			m->usm_batch_base_ofs = xe_migrate_vram_ofs(xe, batch_addr, false);
 		}
 	}
 
···
 
 	/* Identity map the entire vram at 256GiB offset */
 	if (IS_DGFX(xe)) {
-		u64 pt31_ofs = bo->size - XE_PAGE_SIZE;
+		u64 pt30_ofs = bo->size - 2 * XE_PAGE_SIZE;
 
-		xe_migrate_program_identity(xe, vm, bo, map_ofs, 256, pat_index, pt31_ofs);
-		xe_assert(xe, (xe->mem.vram.actual_physical_size <= SZ_256G));
+		xe_migrate_program_identity(xe, vm, bo, map_ofs, IDENTITY_OFFSET,
+					    pat_index, pt30_ofs);
+		xe_assert(xe, xe->mem.vram.actual_physical_size <=
+					(MAX_NUM_PTE - IDENTITY_OFFSET) * SZ_1G);
+
+		/*
+		 * Identity map the entire vram for compressed pat_index for xe2+
+		 * if flat ccs is enabled.
+		 */
+		if (GRAPHICS_VER(xe) >= 20 && xe_device_has_flat_ccs(xe)) {
+			u16 comp_pat_index = xe->pat.idx[XE_CACHE_NONE_COMPRESSION];
+			u64 vram_offset = IDENTITY_OFFSET +
+				DIV_ROUND_UP_ULL(xe->mem.vram.actual_physical_size, SZ_1G);
+			u64 pt31_ofs = bo->size - XE_PAGE_SIZE;
+
+			xe_assert(xe, xe->mem.vram.actual_physical_size <= (MAX_NUM_PTE -
+						IDENTITY_OFFSET - IDENTITY_OFFSET / 2) * SZ_1G);
+			xe_migrate_program_identity(xe, vm, bo, map_ofs, vram_offset,
+						    comp_pat_index, pt31_ofs);
+		}
 	}
 
 	/*
 	 * Example layout created above, with root level = 3:
 	 * [PT0...PT7]: kernel PT's for copy/clear; 64 or 4KiB PTE's
 	 * [PT8]: Kernel PT for VM_BIND, 4 KiB PTE's
-	 * [PT9...PT27]: Userspace PT's for VM_BIND, 4 KiB PTE's
-	 * [PT28 = PDE 0] [PT29 = PDE 1] [PT30 = PDE 2] [PT31 = 2M vram identity map]
+	 * [PT9...PT26]: Userspace PT's for VM_BIND, 4 KiB PTE's
+	 * [PT27 = PDE 0] [PT28 = PDE 1] [PT29 = PDE 2] [PT30 & PT31 = 2M vram identity map]
 	 *
 	 * This makes the lowest part of the VM point to the pagetables.
 	 * Hence the lowest 2M in the vm should point to itself, with a few writes
···
 	return cur->size >= size;
 }
 
+#define PTE_UPDATE_FLAG_IS_VRAM		BIT(0)
+#define PTE_UPDATE_FLAG_IS_COMP_PTE	BIT(1)
+
 static u32 pte_update_size(struct xe_migrate *m,
-			   bool is_vram,
+			   u32 flags,
 			   struct ttm_resource *res,
 			   struct xe_res_cursor *cur,
 			   u64 *L0, u64 *L0_ofs, u32 *L0_pt,
 			   u32 cmd_size, u32 pt_ofs, u32 avail_pts)
 {
 	u32 cmds = 0;
+	bool is_vram = PTE_UPDATE_FLAG_IS_VRAM & flags;
+	bool is_comp_pte = PTE_UPDATE_FLAG_IS_COMP_PTE & flags;
 
 	*L0_pt = pt_ofs;
 	if (is_vram && xe_migrate_allow_identity(*L0, cur)) {
 		/* Offset into identity map. */
 		*L0_ofs = xe_migrate_vram_ofs(tile_to_xe(m->tile),
-					      cur->start + vram_region_gpu_offset(res));
+					      cur->start + vram_region_gpu_offset(res),
+					      is_comp_pte);
 		cmds += cmd_size;
 	} else {
 		/* Clip L0 to available size */
···
 		u32 update_idx;
 		u64 ccs_ofs, ccs_size;
 		u32 ccs_pt;
+		u32 pte_flags;
 
 		bool usm = xe->info.has_usm;
 		u32 avail_pts = max_mem_transfer_per_pass(xe) / LEVEL0_PAGE_TABLE_ENCODE_SIZE;
···
 
 		src_L0 = min(src_L0, dst_L0);
 
-		batch_size += pte_update_size(m, src_is_vram, src, &src_it, &src_L0,
+		pte_flags = src_is_vram ? PTE_UPDATE_FLAG_IS_VRAM : 0;
+		batch_size += pte_update_size(m, pte_flags, src, &src_it, &src_L0,
 					      &src_L0_ofs, &src_L0_pt, 0, 0,
 					      avail_pts);
 
-		batch_size += pte_update_size(m, dst_is_vram, dst, &dst_it, &src_L0,
+		pte_flags = dst_is_vram ? PTE_UPDATE_FLAG_IS_VRAM : 0;
+		batch_size += pte_update_size(m, pte_flags, dst, &dst_it, &src_L0,
 					      &dst_L0_ofs, &dst_L0_pt, 0,
 					      avail_pts, avail_pts);
 
 		if (copy_system_ccs) {
 			ccs_size = xe_device_ccs_bytes(xe, src_L0);
-			batch_size += pte_update_size(m, false, NULL, &ccs_it, &ccs_size,
+			batch_size += pte_update_size(m, 0, NULL, &ccs_it, &ccs_size,
 						      &ccs_ofs, &ccs_pt, 0,
 						      2 * avail_pts,
 						      avail_pts);
···
 		struct xe_sched_job *job;
 		struct xe_bb *bb;
 		u32 batch_size, update_idx;
+		u32 pte_flags;
 
 		bool usm = xe->info.has_usm;
 		u32 avail_pts = max_mem_transfer_per_pass(xe) / LEVEL0_PAGE_TABLE_ENCODE_SIZE;
···
 		clear_L0 = xe_migrate_res_sizes(m, &src_it);
 
 		/* Calculate final sizes and batch size.. */
+		pte_flags = clear_vram ? PTE_UPDATE_FLAG_IS_VRAM : 0;
 		batch_size = 2 +
-			pte_update_size(m, clear_vram, src, &src_it,
+			pte_update_size(m, pte_flags, src, &src_it,
 					&clear_L0, &clear_L0_ofs, &clear_L0_pt,
 					clear_system_ccs ? 0 : emit_clear_cmd_len(gt), 0,
 					avail_pts);
···
 	if (!ppgtt_ofs)
 		ppgtt_ofs = xe_migrate_vram_ofs(tile_to_xe(tile),
 						xe_bo_addr(update->pt_bo, 0,
-							   XE_PAGE_SIZE));
+							   XE_PAGE_SIZE), false);
 
 	do {
 		u64 addr = ppgtt_ofs + ofs * 8;