drm/i915: apply PM_EARLY for non-GTT mappable objects

On DG2 we allow objects that are smaller than the min_page_size, under
the premise that these are never mapped by the GTT, like with the paging
structures. Currently the suspend-resume path will try to map such
objects through the migration vm, which hits:

[ 560.529217] kernel BUG at drivers/gpu/drm/i915/gt/intel_migrate.c:431!
[ 560.536081] invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
[ 560.541629] CPU: 4 PID: 2062 Comm: rtcwake Tainted: G W 5.17.0-rc5-demarchi+ #175
[ 560.550716] Hardware name: Intel Corporation CoffeeLake Client Platform/CoffeeLake S UDIMM RVP, BIOS CNLSFWR1.R00.X220.B00.2103302221 03/30/2021
[ 560.563627] RIP: 0010:emit_pte+0x2e7/0x380 [i915]
[ 560.568665] Code: ee 02 48 89 69 04 83 c6 05 83 c0 05 39 f0 0f 4f c6 48 8b 73 08 39 d0 0f 4f c2 44 89 f2 4c 8d 4a ff 49 85 f1 0f 84 62 fe ff ff <0f> 0b 48 c7 03 00 00 00 00 4d 89 c6 8b 01 48 29 ce 48 8d 57 0c 48
[ 560.587691] RSP: 0018:ffffc9000104f8a0 EFLAGS: 00010206
[ 560.592906] RAX: 0000000000000040 RBX: ffffc9000104f908 RCX: ffffc900025114d0
[ 560.600024] RDX: 0000000000010000 RSI: 00000003f9fe2000 RDI: ffffc900025114dc
[ 560.607458] RBP: 0000000001840000 R08: ffff88810f335540 R09: 000000000000ffff
[ 560.614865] R10: 000000000000081b R11: 0000000000000001 R12: 000000000000081b
[ 560.622300] R13: 0000000000000000 R14: 0000000000010000 R15: ffff888107c3e240
[ 560.629716] FS: 00007f5b7c086580(0000) GS:ffff88846dc00000(0000) knlGS:0000000000000000
[ 560.638090] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 560.644132] CR2: 00007f3ab0a133a8 CR3: 000000010a43e003 CR4: 00000000003706e0
[ 560.651590] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 560.659002] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 560.666438] Call Trace:
[ 560.668885] <TASK>
[ 560.670983] intel_context_migrate_copy+0x1b1/0x4c0 [i915]
[ 560.676794] __i915_ttm_move+0x628/0x790 [i915]
[ 560.681704] ? dma_resv_iter_next+0x8f/0xb0
[ 560.686223] ? dma_resv_iter_first+0xe5/0x140
[ 560.690894] ? i915_deps_add_resv+0x4b/0x110 [i915]
[ 560.696147] ? dma_resv_reserve_shared+0x161/0x310
[ 560.701228] i915_gem_obj_copy_ttm+0x10f/0x220 [i915]
[ 560.706650] i915_ttm_backup+0x191/0x2f0 [i915]
[ 560.711558] i915_gem_process_region+0x266/0x3b0 [i915]
[ 560.717153] ? verify_cpu+0xf0/0x100
[ 560.721040] ? pci_pm_resume_early+0x20/0x20
[ 560.725603] i915_ttm_backup_region+0x47/0x70 [i915]
[ 560.730927] i915_gem_backup_suspend+0x141/0x170 [i91

For now let's just force the memcpy path for such objects during
suspend-resume.

Fixes: 00e27ad85bc9 ("drm/i915/migrate: add acceleration support for DG2")
Reported-by: Lucas De Marchi <[e-mail]>
Signed-off-by: Matthew Auld <[e-mail]>
Cc: Thomas Hellström <[e-mail]>
Reviewed-by: Thomas Hellström <[e-mail]>
Reviewed-by: Lucas De Marchi <[e-mail]>
Signed-off-by: Lucas De Marchi <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/i915/gem/i915_gem_region.c

···
 	if (!obj)
 		return ERR_PTR(-ENOMEM);
 
+	/*
+	 * Anything smaller than the min_page_size can't be freely inserted into
+	 * the GTT, due to alignemnt restrictions. For such special objects,
+	 * make sure we force memcpy based suspend-resume. In the future we can
+	 * revisit this, either by allowing special mis-aligned objects in the
+	 * migration path, or by mapping all of LMEM upfront using cheap 1G
+	 * GTT entries.
+	 */
+	if (default_page_size < mem->min_page_size)
+		flags |= I915_BO_ALLOC_PM_EARLY;
+
 	err = mem->ops->init_object(mem, obj, size, page_size, flags);
 	if (err)
 		goto err_object_free;