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drm/i915/uapi: add NEEDS_CPU_ACCESS hint 

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@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@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: Nirmoy Das <nirmoy.das@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220629174350.384910-6-matthew.auld@intel.com
This commit is contained in:
Matthew Auld 2022-06-29 18:43:43 +01:00
parent 1dbd07e088
commit 525e93f631
2 changed files with 71 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
drivers/gpu/drm/i915/gem/i915_gem_create.c
View File

@ -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,

61
include/uapi/drm/i915_drm.h
View File

@ -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.
*