drm/i915/uapi: expose the avail tracking

Vulkan would like to have a rough measure of how much device memory can
in theory be allocated. Also add unallocated_cpu_visible_size to track
the visible portion, in case the device is using small BAR. Also tweak
the locking so we nice consistent values for both the mm->avail and the
visible tracking.

v2: tweak the locking slightly so we update the mm->avail and visible
tracking as one atomic operation, such that userspace doesn't get
strange values when sampling the values.

Testcase: igt@i915_query@query-regions-unallocated
Testcase: igt@i915_query@query-regions-sanity-check
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Jon Bloomfield <jon.bloomfield@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Kenneth Graunke <kenneth@whitecape.org>
Cc: Akeem G Abodunrin <akeem.g.abodunrin@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220629174350.384910-3-matthew.auld@intel.com

drivers/gpu/drm/i915/i915_query.c

@@ -504,7 +504,15 @@ static int query_memregion_info(struct drm_i915_private *i915,
 		else
 			info.probed_cpu_visible_size = mr->total;
 
-		info.unallocated_size = mr->avail;
+		if (perfmon_capable()) {
+			intel_memory_region_avail(mr,
+						  &info.unallocated_size,
+						  &info.unallocated_cpu_visible_size);
+		} else {
+			info.unallocated_size = info.probed_size;
+			info.unallocated_cpu_visible_size =
+				info.probed_cpu_visible_size;
+		}
 
 		if (__copy_to_user(info_ptr, &info, sizeof(info)))
 			return -EFAULT;

drivers/gpu/drm/i915/i915_ttm_buddy_manager.c

@@ -104,18 +104,15 @@ static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager *man,
 				     min_page_size,
 				     &bman_res->blocks,
 				     bman_res->flags);
-	mutex_unlock(&bman->lock);
 	if (unlikely(err))
 		goto err_free_blocks;
 
 	if (place->flags & TTM_PL_FLAG_CONTIGUOUS) {
 		u64 original_size = (u64)bman_res->base.num_pages << PAGE_SHIFT;
 
-		mutex_lock(&bman->lock);
 		drm_buddy_block_trim(mm,
 				     original_size,
 				     &bman_res->blocks);
-		mutex_unlock(&bman->lock);
 	}
 
 	if (lpfn <= bman->visible_size) {
@@ -137,11 +134,10 @@ static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager *man,
 		}
 	}
 
-	if (bman_res->used_visible_size) {
-		mutex_lock(&bman->lock);
+	if (bman_res->used_visible_size)
 		bman->visible_avail -= bman_res->used_visible_size;
+
 	mutex_unlock(&bman->lock);
-	}
 
 	if (place->lpfn - place->fpfn == n_pages)
 		bman_res->base.start = place->fpfn;
@@ -154,7 +150,6 @@ static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager *man,
 	return 0;
 
 err_free_blocks:
-	mutex_lock(&bman->lock);
 	drm_buddy_free_list(mm, &bman_res->blocks);
 	mutex_unlock(&bman->lock);
 err_free_res:
@@ -365,6 +360,26 @@ u64 i915_ttm_buddy_man_visible_size(struct ttm_resource_manager *man)
 	return bman->visible_size;
 }
 
+/**
+ * i915_ttm_buddy_man_avail - Query the avail tracking for the manager.
+ *
+ * @man: The buddy allocator ttm manager
+ * @avail: The total available memory in pages for the entire manager.
+ * @visible_avail: The total available memory in pages for the CPU visible
+ * portion. Note that this will always give the same value as @avail on
+ * configurations that don't have a small BAR.
+ */
+void i915_ttm_buddy_man_avail(struct ttm_resource_manager *man,
+			      u64 *avail, u64 *visible_avail)
+{
+	struct i915_ttm_buddy_manager *bman = to_buddy_manager(man);
+
+	mutex_lock(&bman->lock);
+	*avail = bman->mm.avail >> PAGE_SHIFT;
+	*visible_avail = bman->visible_avail;
+	mutex_unlock(&bman->lock);
+}
+
 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
 void i915_ttm_buddy_man_force_visible_size(struct ttm_resource_manager *man,
 					   u64 size)

drivers/gpu/drm/i915/i915_ttm_buddy_manager.h

@@ -61,6 +61,9 @@ int i915_ttm_buddy_man_reserve(struct ttm_resource_manager *man,
 
 u64 i915_ttm_buddy_man_visible_size(struct ttm_resource_manager *man);
 
+void i915_ttm_buddy_man_avail(struct ttm_resource_manager *man,
+			      u64 *avail, u64 *avail_visible);
+
 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
 void i915_ttm_buddy_man_force_visible_size(struct ttm_resource_manager *man,
 					   u64 size);

drivers/gpu/drm/i915/intel_memory_region.c

@@ -279,6 +279,20 @@ void intel_memory_region_set_name(struct intel_memory_region *mem,
 	va_end(ap);
 }
 
+void intel_memory_region_avail(struct intel_memory_region *mr,
+			       u64 *avail, u64 *visible_avail)
+{
+	if (mr->type == INTEL_MEMORY_LOCAL) {
+		i915_ttm_buddy_man_avail(mr->region_private,
+					 avail, visible_avail);
+		*avail <<= PAGE_SHIFT;
+		*visible_avail <<= PAGE_SHIFT;
+	} else {
+		*avail = mr->total;
+		*visible_avail = mr->total;
+	}
+}
+
 void intel_memory_region_destroy(struct intel_memory_region *mem)
 {
 	int ret = 0;

drivers/gpu/drm/i915/intel_memory_region.h

@@ -127,6 +127,9 @@ int intel_memory_region_reserve(struct intel_memory_region *mem,
 void intel_memory_region_debug(struct intel_memory_region *mr,
 			       struct drm_printer *printer);
 
+void intel_memory_region_avail(struct intel_memory_region *mr,
+			       u64 *avail, u64 *visible_avail);
+
 struct intel_memory_region *
 i915_gem_ttm_system_setup(struct drm_i915_private *i915,
 			  u16 type, u16 instance);

include/uapi/drm/i915_drm.h

@@ -3228,7 +3228,15 @@ struct drm_i915_memory_region_info {
 	 */
 	__u64 probed_size;
 
-	/** @unallocated_size: Estimate of memory remaining */
+	/**
+	 * @unallocated_size: Estimate of memory remaining
+	 *
+	 * Requires CAP_PERFMON or CAP_SYS_ADMIN to get reliable accounting.
+	 * Without this (or if this is an older kernel) the value here will
+	 * always equal the @probed_size. Note this is only currently tracked
+	 * for I915_MEMORY_CLASS_DEVICE regions (for other types the value here
+	 * will always equal the @probed_size).
+	 */
 	__u64 unallocated_size;
 
 	union {
@@ -3262,6 +3270,27 @@ struct drm_i915_memory_region_info {
 			 * @probed_size.
 			 */
 			__u64 probed_cpu_visible_size;
+
+			/**
+			 * @unallocated_cpu_visible_size: Estimate of CPU
+			 * visible memory remaining.
+			 *
+			 * Note this is only tracked for
+			 * I915_MEMORY_CLASS_DEVICE regions (for other types the
+			 * value here will always equal the
+			 * @probed_cpu_visible_size).
+			 *
+			 * Requires CAP_PERFMON or CAP_SYS_ADMIN to get reliable
+			 * accounting.  Without this the value here will always
+			 * equal the @probed_cpu_visible_size. Note this is only
+			 * currently tracked for I915_MEMORY_CLASS_DEVICE
+			 * regions (for other types the value here will also
+			 * always equal the @probed_cpu_visible_size).
+			 *
+			 * If this is an older kernel the value here will be
+			 * zero, see also @probed_cpu_visible_size.
+			 */
+			__u64 unallocated_cpu_visible_size;
 		};
 	};
 };