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Add an entry for the new uapi needed for small BAR on DG2+.
v2:
- Some spelling fixes and other small tweaks. (Akeem & Thomas)
- Rework error capture interactions, including no longer needing
NEEDS_CPU_ACCESS for objects marked for capture. (Thomas)
- Add probed_cpu_visible_size. (Lionel)
v3:
- Drop the vma query for now.
- Add unallocated_cpu_visible_size as part of the region query.
- Improve the docs some more, including documenting the expected
behaviour on older kernels, since this came up in some offline
discussion.
v4:
- Various improvements all over. (Tvrtko)
v5:
- Include newer integrated platforms when applying the non-recoverable
context and error capture restriction. (Thomas)
Mesa: https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16739
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>
Cc: mesa-dev@lists.freedesktop.org
Acked-by: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Acked-by: Akeem G Abodunrin <akeem.g.abodunrin@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Acked-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Acked-by: Jordan Justen <jordan.l.justen@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220629174350.384910-1-matthew.auld@intel.com
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48 lines
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==========================
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I915 Small BAR RFC Section
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==========================
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Starting from DG2 we will have resizable BAR support for device local-memory(i.e
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I915_MEMORY_CLASS_DEVICE), but in some cases the final BAR size might still be
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smaller than the total probed_size. In such cases, only some subset of
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I915_MEMORY_CLASS_DEVICE will be CPU accessible(for example the first 256M),
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while the remainder is only accessible via the GPU.
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I915_GEM_CREATE_EXT_FLAG_NEEDS_CPU_ACCESS flag
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----------------------------------------------
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New gem_create_ext flag to tell the kernel that a BO will require CPU access.
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This becomes important when placing an object in I915_MEMORY_CLASS_DEVICE, where
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underneath the device has a small BAR, meaning only some portion of it is CPU
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accessible. Without this flag the kernel will assume that CPU access is not
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required, and prioritize using the non-CPU visible portion of
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I915_MEMORY_CLASS_DEVICE.
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.. kernel-doc:: Documentation/gpu/rfc/i915_small_bar.h
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:functions: __drm_i915_gem_create_ext
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probed_cpu_visible_size attribute
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---------------------------------
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New struct__drm_i915_memory_region attribute which returns the total size of the
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CPU accessible portion, for the particular region. This should only be
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applicable for I915_MEMORY_CLASS_DEVICE. We also report the
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unallocated_cpu_visible_size, alongside the unallocated_size.
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Vulkan will need this as part of creating a separate VkMemoryHeap with the
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VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT set, to represent the CPU visible portion,
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where the total size of the heap needs to be known. It also wants to be able to
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give a rough estimate of how memory can potentially be allocated.
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.. kernel-doc:: Documentation/gpu/rfc/i915_small_bar.h
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:functions: __drm_i915_memory_region_info
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Error Capture restrictions
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--------------------------
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With error capture we have two new restrictions:
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1) Error capture is best effort on small BAR systems; if the pages are not
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CPU accessible, at the time of capture, then the kernel is free to skip
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trying to capture them.
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2) On discrete and newer integrated platforms we now reject error capture
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on recoverable contexts. In the future the kernel may want to blit during
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error capture, when for example something is not currently CPU accessible.
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