If set, force the allocation to be placed in the mappable portion of
I915_MEMORY_CLASS_DEVICE. One big restriction here is that system memory
(i.e I915_MEMORY_CLASS_SYSTEM) must be given as a potential placement for the
object, that way we can always spill the object into system memory if we
can't make space.
Testcase: igt@gem-create@create-ext-cpu-access-sanity-check
Testcase: igt@gem-create@create-ext-cpu-access-big
Signed-off-by: Matthew Auld <matthew.auld@xxxxxxxxx>
Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
Cc: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>
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/gem/i915_gem_create.c | 26 ++++++---
include/uapi/drm/i915_drm.h | 61 +++++++++++++++++++---
2 files changed, 71 insertions(+), 16 deletions(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_create.c b/drivers/gpu/drm/i915/gem/i915_gem_create.c
index d094cae0ddf1..33673fe7ee0a 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_create.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_create.c
@@ -241,6 +241,7 @@ struct create_ext {
struct drm_i915_private *i915;
struct intel_memory_region *placements[INTEL_REGION_UNKNOWN];
unsigned int n_placements;
+ unsigned int placement_mask;
unsigned long flags;
};
@@ -337,6 +338,7 @@ static int set_placements(struct drm_i915_gem_create_ext_memory_regions *args,
for (i = 0; i < args->num_regions; i++)
ext_data->placements[i] = placements[i];
+ ext_data->placement_mask = mask;
return 0;
out_dump:
@@ -411,7 +413,7 @@ i915_gem_create_ext_ioctl(struct drm_device *dev, void *data,
struct drm_i915_gem_object *obj;
int ret;
- if (args->flags)
+ if (args->flags & ~I915_GEM_CREATE_EXT_FLAG_NEEDS_CPU_ACCESS)
return -EINVAL;
ret = i915_user_extensions(u64_to_user_ptr(args->extensions),
@@ -427,13 +429,21 @@ i915_gem_create_ext_ioctl(struct drm_device *dev, void *data,
ext_data.n_placements = 1;
}
- /*
- * TODO: add a userspace hint to force CPU_ACCESS for the object, which
- * can override this.
- */
- if (ext_data.n_placements > 1 ||
- ext_data.placements[0]->type != INTEL_MEMORY_SYSTEM)
- ext_data.flags |= I915_BO_ALLOC_GPU_ONLY;
+ if (args->flags & I915_GEM_CREATE_EXT_FLAG_NEEDS_CPU_ACCESS) {
+ if (ext_data.n_placements == 1)
+ return -EINVAL;
+
+ /*
+ * We always need to be able to spill to system memory, if we
+ * can't place in the mappable part of LMEM.
+ */
+ if (!(ext_data.placement_mask & BIT(INTEL_REGION_SMEM)))
+ return -EINVAL;
+ } else {
+ if (ext_data.n_placements > 1 ||
+ ext_data.placements[0]->type != INTEL_MEMORY_SYSTEM)
+ ext_data.flags |= I915_BO_ALLOC_GPU_ONLY;
+ }
obj = __i915_gem_object_create_user_ext(i915, args->size,
ext_data.placements,
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index e30f31a440b3..5b0a10e6a1b8 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -3366,11 +3366,11 @@ struct drm_i915_query_memory_regions {
* struct drm_i915_gem_create_ext - Existing gem_create behaviour, with added
* extension support using struct i915_user_extension.
*
- * Note that in the future we want to have our buffer flags here, at least for
- * the stuff that is immutable. Previously we would have two ioctls, one to
- * create the object with gem_create, and another to apply various parameters,
- * however this creates some ambiguity for the params which are considered
- * immutable. Also in general we're phasing out the various SET/GET ioctls.
+ * Note that new buffer flags should be added here, at least for the stuff that
+ * is immutable. Previously we would have two ioctls, one to create the object
+ * with gem_create, and another to apply various parameters, however this
+ * creates some ambiguity for the params which are considered immutable. Also in
+ * general we're phasing out the various SET/GET ioctls.
*/
struct drm_i915_gem_create_ext {
/**
@@ -3378,7 +3378,6 @@ struct drm_i915_gem_create_ext {
*
* The (page-aligned) allocated size for the object will be returned.
*
- *
* DG2 64K min page size implications:
*
* On discrete platforms, starting from DG2, we have to contend with GTT
@@ -3390,7 +3389,9 @@ struct drm_i915_gem_create_ext {
*
* Note that the returned size here will always reflect any required
* rounding up done by the kernel, i.e 4K will now become 64K on devices
- * such as DG2.
+ * such as DG2. The kernel will always select the largest minimum
+ * page-size for the set of possible placements as the value to use when
+ * rounding up the @size.
*
* Special DG2 GTT address alignment requirement:
*
@@ -3414,14 +3415,58 @@ struct drm_i915_gem_create_ext {
* is deemed to be a good compromise.
*/
__u64 size;
+
/**
* @handle: Returned handle for the object.
*
* Object handles are nonzero.
*/
__u32 handle;
- /** @flags: MBZ */
+
+ /**
+ * @flags: Optional flags.
+ *
+ * Supported values:
+ *
+ * I915_GEM_CREATE_EXT_FLAG_NEEDS_CPU_ACCESS - Signal to the kernel that
+ * the object will need to be accessed via the CPU.
+ *
+ * Only valid when placing objects in I915_MEMORY_CLASS_DEVICE, and only
+ * strictly required on configurations where some subset of the device
+ * memory is directly visible/mappable through the CPU (which we also
+ * call small BAR), like on some DG2+ systems. Note that this is quite
+ * undesirable, but due to various factors like the client CPU, BIOS etc
+ * it's something we can expect to see in the wild. See
+ * &drm_i915_memory_region_info.probed_cpu_visible_size for how to
+ * determine if this system applies.
+ *
+ * Note that one of the placements MUST be I915_MEMORY_CLASS_SYSTEM, to
+ * ensure the kernel can always spill the allocation to system memory,
+ * if the object can't be allocated in the mappable part of
+ * I915_MEMORY_CLASS_DEVICE.
+ *
+ * Also note that since the kernel only supports flat-CCS on objects
+ * that can *only* be placed in I915_MEMORY_CLASS_DEVICE, we therefore
+ * don't support I915_GEM_CREATE_EXT_FLAG_NEEDS_CPU_ACCESS together with
+ * flat-CCS.
+ *
+ * Without this hint, the kernel will assume that non-mappable
+ * I915_MEMORY_CLASS_DEVICE is preferred for this object. Note that the
+ * kernel can still migrate the object to the mappable part, as a last
+ * resort, if userspace ever CPU faults this object, but this might be
+ * expensive, and so ideally should be avoided.
+ *
+ * On older kernels which lack the relevant small-bar uAPI support (see
+ * also &drm_i915_memory_region_info.probed_cpu_visible_size),
+ * usage of the flag will result in an error, but it should NEVER be
+ * possible to end up with a small BAR configuration, assuming we can
+ * also successfully load the i915 kernel module. In such cases the
+ * entire I915_MEMORY_CLASS_DEVICE region will be CPU accessible, and as
+ * such there are zero restrictions on where the object can be placed.
+ */
+#define I915_GEM_CREATE_EXT_FLAG_NEEDS_CPU_ACCESS (1 << 0)
__u32 flags;
+
/**
* @extensions: The chain of extensions to apply to this object.
*
