Re: [PATCH 03/10] drm/i915/uapi: expose the avail tracking

Matthew Auld <matthew.auld@xxxxxxxxx> · Thu, 26 May 2022 09:10:35 +0100

On 26/05/2022 08:58, Tvrtko Ursulin wrote:

On 25/05/2022 19:43, Matthew Auld wrote:
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.

I have concerns here that it isn't useful and could even be 
counter-productive. If we give unprivileged access it may be considered 
a side channel, but if we "lie" (report total region size) to 
unprivileged clients (like in this patch), then they don't co-operate 
well and end trashing.

Is Vulkan really sure it wants this and why?

Lionel pointed out: 
https://www.khronos.org/registry/vulkan/specs/1.3-extensions/man/html/VK_EXT_memory_budget.html

Also note that the existing behaviour was to lie. I'm not sure what's 
the best option here.


Regards,

Tvrtko

Testcase: igt@i915_query@query-regions-unallocated
Testcase: igt@i915_query@query-regions-sanity-check
Signed-off-by: Matthew Auld <matthew.auld@xxxxxxxxx>
Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
Cc: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>
Cc: Jon Bloomfield <jon.bloomfield@xxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Jordan Justen <jordan.l.justen@xxxxxxxxx>
Cc: Kenneth Graunke <kenneth@xxxxxxxxxxxxx>
Cc: Akeem G Abodunrin <akeem.g.abodunrin@xxxxxxxxx>
---
  drivers/gpu/drm/i915/i915_query.c             | 10 +++++-
  drivers/gpu/drm/i915/i915_ttm_buddy_manager.c | 20 ++++++++++++
  drivers/gpu/drm/i915/i915_ttm_buddy_manager.h |  3 ++
  drivers/gpu/drm/i915/intel_memory_region.c    | 14 +++++++++
  drivers/gpu/drm/i915/intel_memory_region.h    |  3 ++
  include/uapi/drm/i915_drm.h                   | 31 ++++++++++++++++++-
  6 files changed, 79 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_query.c 
b/drivers/gpu/drm/i915/i915_query.c
index 9aa0b28aa6ee..e095c55f4d4b 100644
--- a/drivers/gpu/drm/i915/i915_query.c
+++ b/drivers/gpu/drm/i915/i915_query.c
@@ -502,7 +502,15 @@ 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;
diff --git a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c 
b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
index a5109548abc0..aa5c91e44438 100644
--- a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
+++ b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
@@ -365,6 +365,26 @@ u64 i915_ttm_buddy_man_visible_size(struct 
ttm_resource_manager *man)
      return bman->visible_size;
  }
+/**
+ * i915_ttm_buddy_man_visible_size - 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)
diff --git a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.h 
b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.h
index 52d9586d242c..d64620712830 100644
--- a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.h
+++ b/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);
diff --git a/drivers/gpu/drm/i915/intel_memory_region.c 
b/drivers/gpu/drm/i915/intel_memory_region.c
index e38d2db1c3e3..94ee26e99549 100644
--- a/drivers/gpu/drm/i915/intel_memory_region.c
+++ b/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;
diff --git a/drivers/gpu/drm/i915/intel_memory_region.h 
b/drivers/gpu/drm/i915/intel_memory_region.h
index 3d8378c1b447..2214f251bec3 100644
--- a/drivers/gpu/drm/i915/intel_memory_region.h
+++ b/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);
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 9df419a45244..e30f31a440b3 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/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 (-1 = 
unknown) */
+    /**
+     * @unallocated_size: Estimate of memory remaining (-1 = unknown)
+     *
+     * 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 (-1 = unknown).
+             *
+             * 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;
          };
      };
  };






