48 lines
2.2 KiB
ReStructuredText
48 lines
2.2 KiB
ReStructuredText
|
==========================
|
||
|
|
I915 Small BAR RFC Section
|
||
|
|
==========================
|
||
|
|
Starting from DG2 we will have resizable BAR support for device local-memory(i.e
|
||
|
|
I915_MEMORY_CLASS_DEVICE), but in some cases the final BAR size might still be
|
||
|
|
smaller than the total probed_size. In such cases, only some subset of
|
||
|
|
I915_MEMORY_CLASS_DEVICE will be CPU accessible(for example the first 256M),
|
||
|
|
while the remainder is only accessible via the GPU.
|
||
|
|
|
||
|
|
I915_GEM_CREATE_EXT_FLAG_NEEDS_CPU_ACCESS flag
|
||
|
|
----------------------------------------------
|
||
|
|
New gem_create_ext flag to tell the kernel that a BO will require CPU access.
|
||
|
|
This becomes important when placing an object in I915_MEMORY_CLASS_DEVICE, where
|
||
|
|
underneath the device has a small BAR, meaning only some portion of it is CPU
|
||
|
|
accessible. Without this flag the kernel will assume that CPU access is not
|
||
|
|
required, and prioritize using the non-CPU visible portion of
|
||
|
|
I915_MEMORY_CLASS_DEVICE.
|
||
|
|
|
||
|
|
.. kernel-doc:: Documentation/gpu/rfc/i915_small_bar.h
|
||
|
|
:functions: __drm_i915_gem_create_ext
|
||
|
|
|
||
|
|
probed_cpu_visible_size attribute
|
||
|
|
---------------------------------
|
||
|
|
New struct__drm_i915_memory_region attribute which returns the total size of the
|
||
|
|
CPU accessible portion, for the particular region. This should only be
|
||
|
|
applicable for I915_MEMORY_CLASS_DEVICE. We also report the
|
||
|
|
unallocated_cpu_visible_size, alongside the unallocated_size.
|
||
|
|
|
||
|
|
Vulkan will need this as part of creating a separate VkMemoryHeap with the
|
||
|
|
VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT set, to represent the CPU visible portion,
|
||
|
|
where the total size of the heap needs to be known. It also wants to be able to
|
||
|
|
give a rough estimate of how memory can potentially be allocated.
|
||
|
|
|
||
|
|
.. kernel-doc:: Documentation/gpu/rfc/i915_small_bar.h
|
||
|
|
:functions: __drm_i915_memory_region_info
|
||
|
|
|
||
|
|
Error Capture restrictions
|
||
|
|
--------------------------
|
||
|
|
With error capture we have two new restrictions:
|
||
|
|
|
||
|
|
1) Error capture is best effort on small BAR systems; if the pages are not
|
||
|
|
CPU accessible, at the time of capture, then the kernel is free to skip
|
||
|
|
trying to capture them.
|
||
|
|
|
||
|
|
2) On discrete and newer integrated platforms we now reject error capture
|
||
|
|
on recoverable contexts. In the future the kernel may want to blit during
|
||
|
|
error capture, when for example something is not currently CPU accessible.
|