[Intel-gfx] [PATCH v6 3/3] drm/doc/rfc: VM_BIND uapi definition
Jason Ekstrand
jason at jlekstrand.net
Thu Jun 30 15:34:59 UTC 2022
On Thu, Jun 30, 2022 at 10:14 AM Matthew Auld <matthew.auld at intel.com>
wrote:
> On 30/06/2022 06:11, Jason Ekstrand wrote:
> > On Sat, Jun 25, 2022 at 8:49 PM Niranjana Vishwanathapura
> > <niranjana.vishwanathapura at intel.com
> > <mailto:niranjana.vishwanathapura at intel.com>> wrote:
> >
> > VM_BIND and related uapi definitions
> >
> > v2: Reduce the scope to simple Mesa use case.
> > v3: Expand VM_UNBIND documentation and add
> > I915_GEM_VM_BIND/UNBIND_FENCE_VALID
> > and I915_GEM_VM_BIND_TLB_FLUSH flags.
> > v4: Remove I915_GEM_VM_BIND_TLB_FLUSH flag and add additional
> > documentation for vm_bind/unbind.
> > v5: Remove TLB flush requirement on VM_UNBIND.
> > Add version support to stage implementation.
> > v6: Define and use drm_i915_gem_timeline_fence structure for
> > all timeline fences.
> > v7: Rename I915_PARAM_HAS_VM_BIND to I915_PARAM_VM_BIND_VERSION.
> > Update documentation on async vm_bind/unbind and versioning.
> > Remove redundant vm_bind/unbind FENCE_VALID flag, execbuf3
> > batch_count field and I915_EXEC3_SECURE flag.
> >
> > Signed-off-by: Niranjana Vishwanathapura
> > <niranjana.vishwanathapura at intel.com
> > <mailto:niranjana.vishwanathapura at intel.com>>
> > Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch
> > <mailto:daniel.vetter at ffwll.ch>>
> > ---
> > Documentation/gpu/rfc/i915_vm_bind.h | 280
> +++++++++++++++++++++++++++
> > 1 file changed, 280 insertions(+)
> > create mode 100644 Documentation/gpu/rfc/i915_vm_bind.h
> >
> > diff --git a/Documentation/gpu/rfc/i915_vm_bind.h
> > b/Documentation/gpu/rfc/i915_vm_bind.h
> > new file mode 100644
> > index 000000000000..a93e08bceee6
> > --- /dev/null
> > +++ b/Documentation/gpu/rfc/i915_vm_bind.h
> > @@ -0,0 +1,280 @@
> > +/* SPDX-License-Identifier: MIT */
> > +/*
> > + * Copyright © 2022 Intel Corporation
> > + */
> > +
> > +/**
> > + * DOC: I915_PARAM_VM_BIND_VERSION
> > + *
> > + * VM_BIND feature version supported.
> > + * See typedef drm_i915_getparam_t param.
> > + *
> > + * Specifies the VM_BIND feature version supported.
> > + * The following versions of VM_BIND have been defined:
> > + *
> > + * 0: No VM_BIND support.
> > + *
> > + * 1: In VM_UNBIND calls, the UMD must specify the exact mappings
> > created
> > + * previously with VM_BIND, the ioctl will not support unbinding
> > multiple
> > + * mappings or splitting them. Similarly, VM_BIND calls will not
> > replace
> > + * any existing mappings.
> > + *
> > + * 2: The restrictions on unbinding partial or multiple mappings is
> > + * lifted, Similarly, binding will replace any mappings in the
> > given range.
> > + *
> > + * See struct drm_i915_gem_vm_bind and struct
> drm_i915_gem_vm_unbind.
> > + */
> > +#define I915_PARAM_VM_BIND_VERSION 57
> > +
> > +/**
> > + * DOC: I915_VM_CREATE_FLAGS_USE_VM_BIND
> > + *
> > + * Flag to opt-in for VM_BIND mode of binding during VM creation.
> > + * See struct drm_i915_gem_vm_control flags.
> > + *
> > + * The older execbuf2 ioctl will not support VM_BIND mode of
> operation.
> > + * For VM_BIND mode, we have new execbuf3 ioctl which will not
> > accept any
> > + * execlist (See struct drm_i915_gem_execbuffer3 for more details).
> > + */
> > +#define I915_VM_CREATE_FLAGS_USE_VM_BIND (1 << 0)
> > +
> > +/* VM_BIND related ioctls */
> > +#define DRM_I915_GEM_VM_BIND 0x3d
> > +#define DRM_I915_GEM_VM_UNBIND 0x3e
> > +#define DRM_I915_GEM_EXECBUFFER3 0x3f
> > +
> > +#define DRM_IOCTL_I915_GEM_VM_BIND
> > DRM_IOWR(DRM_COMMAND_BASE + DRM_I915_GEM_VM_BIND, struct
> > drm_i915_gem_vm_bind)
> > +#define DRM_IOCTL_I915_GEM_VM_UNBIND
> > DRM_IOWR(DRM_COMMAND_BASE + DRM_I915_GEM_VM_UNBIND, struct
> > drm_i915_gem_vm_bind)
> > +#define DRM_IOCTL_I915_GEM_EXECBUFFER3
> > DRM_IOWR(DRM_COMMAND_BASE + DRM_I915_GEM_EXECBUFFER3, struct
> > drm_i915_gem_execbuffer3)
> > +
> > +/**
> > + * struct drm_i915_gem_timeline_fence - An input or output timeline
> > fence.
> > + *
> > + * The operation will wait for input fence to signal.
> > + *
> > + * The returned output fence will be signaled after the completion
> > of the
> > + * operation.
> > + */
> > +struct drm_i915_gem_timeline_fence {
> > + /** @handle: User's handle for a drm_syncobj to wait on or
> > signal. */
> > + __u32 handle;
> > +
> > + /**
> > + * @flags: Supported flags are:
> > + *
> > + * I915_TIMELINE_FENCE_WAIT:
> > + * Wait for the input fence before the operation.
> > + *
> > + * I915_TIMELINE_FENCE_SIGNAL:
> > + * Return operation completion fence as output.
> > + */
> > + __u32 flags;
> > +#define I915_TIMELINE_FENCE_WAIT (1 << 0)
> > +#define I915_TIMELINE_FENCE_SIGNAL (1 << 1)
> > +#define __I915_TIMELINE_FENCE_UNKNOWN_FLAGS
> > (-(I915_TIMELINE_FENCE_SIGNAL << 1))
> > +
> > + /**
> > + * @value: A point in the timeline.
> > + * Value must be 0 for a binary drm_syncobj. A Value of 0
> for a
> > + * timeline drm_syncobj is invalid as it turns a drm_syncobj
> > into a
> > + * binary one.
> > + */
> > + __u64 value;
> > +};
> > +
> > +/**
> > + * struct drm_i915_gem_vm_bind - VA to object mapping to bind.
> > + *
> > + * This structure is passed to VM_BIND ioctl and specifies the
> > mapping of GPU
> > + * virtual address (VA) range to the section of an object that
> > should be bound
> > + * in the device page table of the specified address space (VM).
> > + * The VA range specified must be unique (ie., not currently bound)
> > and can
> > + * be mapped to whole object or a section of the object (partial
> > binding).
> > + * Multiple VA mappings can be created to the same section of the
> > object
> > + * (aliasing).
> > + *
> > + * The @start, @offset and @length must be 4K page aligned. However
> > the DG2
> > + * and XEHPSDV has 64K page size for device local-memory and has
> > compact page
> > + * table. On those platforms, for binding device local-memory
> > objects, the
> > + * @start must be 2M aligned, @offset and @length must be 64K
> aligned.
> >
> >
> > This is not acceptable. We need 64K granularity. This includes the
> > starting address, the BO offset, and the length. Why? The tl;dr is
> > that it's a requirement for about 50% of D3D12 apps if we want them to
> > run on Linux via D3D12. A longer explanation follows. I don't
> > necessarily expect kernel folks to get all the details but hopefully
> > I'll have left enough of a map that some of the Intel Mesa folks can
> > help fill in details.
> >
> > Many modern D3D12 apps have a hard requirement on Tier2 tiled
> > resources. This is a feature that Intel has supported in the D3D12
> > driver since Skylake. In order to implement this feature, VKD3D
> > requires the various sparseResidencyImage* and sparseResidency*Sampled
> > Vulkan features. If we want those apps to work (there's getting to be
> > quite a few of them), we need to implement the Vulkan sparse residency
> > features.
> > |
> > |
> > What is sparse residency? I'm glad you asked! The sparse residency
> > features allow a client to separately bind each miplevel or array slice
> > of an image to a chunk of device memory independently, without affecting
> > any other areas of the image. Once you get to a high enough miplevel
> > that everything fits inside a single sparse image block (that's a
> > technical Vulkan term you can search for in the spec), you can enter a
> > "miptail" which contains all the remaining miplevels in a single sparse
> > image block.
> >
> > The term "sparse image block" is what the Vulkan spec uses. On Intel
> > hardware and in the docs, it's what we call a "tile". Specifically, the
> > image needs to use Yf or Ys tiling on SKL-TGL or a Tile64 on DG2+. This
> > is because Tile4 and legacy X and Y-tiling don't provide any guarantees
> > about page alignment for slices. Yf, Ys, and Tile64, on the other hand,
> > align all slices of the image to a tile boundary, allowing us to map
> > memory to different slices independently, assuming we have 64K (or 4K
> > for Yf) VM_BIND granularity. (4K isn't actually a requirement for
> > SKL-TGL; we can use Ys all the time which has 64K tiles but there's no
> > reason to not support 4K alignments on integrated.)
> >
> > Someone may be tempted to ask, "Can't we wiggle the strides around or
> > something to make it work?" I thought about that and no, you can't.
> > The problem here is LOD2+. Sure, you can have a stride such that the
> > image is a multiple of 2M worth of tiles across. That'll work fine for
> > LOD0 and LOD1; both will be 2M aligned. However, LOD2 won't be and
> > there's no way to control that. The hardware will place it to the right
> > of LOD1 by ROUND_UP(width, tile_width) pixels and there's nothing you
> > can do about that. If that position doesn't happen to hit a 2M
> > boundary, you're out of luck.
> >
> > I hope that explanation provides enough detail. Sadly, this is one of
> > those things which has a lot of moving pieces all over different bits of
> > the hardware and various APIs and they all have to work together just
> > right for it to all come out in the end. But, yeah, we really need 64K
> > aligned binding if we want VKD3D to work.
>
> Just to confirm, the new model would be to enforce 64K GTT alignment for
> lmem pages, and then for smem pages we would only require 4K alignment,
> but with the added restriction that userspace will never try to mix the
> two (lmem vs smem) within the same 2M va range (page-table). The kernel
> will verify this and throw an error if needed. This model should work
> with the above?
>
Mesa doesn't have full control over BO placement so I don't think we can
guarantee quite as much as you want there. We can guarantee, I think, that
we never place LMEM-only and SMEM-only in the same 2M block. However, most
BOs will be LMEM+SMEM (with a preference for LMEM) and then it'll be up to
the kernel to sort out any issues. Is that reasonable?
--Jason
> >
> > --Jason
> >
> > + * Also, for such mappings, i915 will reserve the whole 2M range
> > for it so as
> > + * to not allow multiple mappings in that 2M range (Compact page
> > tables do not
> > + * allow 64K page and 4K page bindings in the same 2M range).
> > + *
> > + * Error code -EINVAL will be returned if @start, @offset and
> > @length are not
> > + * properly aligned. In version 1 (See I915_PARAM_VM_BIND_VERSION),
> > error code
> > + * -ENOSPC will be returned if the VA range specified can't be
> > reserved.
> > + *
> > + * VM_BIND/UNBIND ioctl calls executed on different CPU threads
> > concurrently
> > + * are not ordered. Furthermore, parts of the VM_BIND operation can
> > be done
> > + * asynchronously, if valid @fence is specified.
> > + */
> > +struct drm_i915_gem_vm_bind {
> > + /** @vm_id: VM (address space) id to bind */
> > + __u32 vm_id;
> > +
> > + /** @handle: Object handle */
> > + __u32 handle;
> > +
> > + /** @start: Virtual Address start to bind */
> > + __u64 start;
> > +
> > + /** @offset: Offset in object to bind */
> > + __u64 offset;
> > +
> > + /** @length: Length of mapping to bind */
> > + __u64 length;
> > +
> > + /**
> > + * @flags: Supported flags are:
> > + *
> > + * I915_GEM_VM_BIND_READONLY:
> > + * Mapping is read-only.
> > + *
> > + * I915_GEM_VM_BIND_CAPTURE:
> > + * Capture this mapping in the dump upon GPU error.
> > + */
> > + __u64 flags;
> > +#define I915_GEM_VM_BIND_READONLY (1 << 1)
> > +#define I915_GEM_VM_BIND_CAPTURE (1 << 2)
> > +
> > + /**
> > + * @fence: Timeline fence for bind completion signaling.
> > + *
> > + * It is an out fence, hence using I915_TIMELINE_FENCE_WAIT
> flag
> > + * is invalid, and an error will be returned.
> > + */
> > + struct drm_i915_gem_timeline_fence fence;
> > +
> > + /**
> > + * @extensions: Zero-terminated chain of extensions.
> > + *
> > + * For future extensions. See struct i915_user_extension.
> > + */
> > + __u64 extensions;
> > +};
> > +
> > +/**
> > + * struct drm_i915_gem_vm_unbind - VA to object mapping to unbind.
> > + *
> > + * This structure is passed to VM_UNBIND ioctl and specifies the
> > GPU virtual
> > + * address (VA) range that should be unbound from the device page
> > table of the
> > + * specified address space (VM). VM_UNBIND will force unbind the
> > specified
> > + * range from device page table without waiting for any GPU job to
> > complete.
> > + * It is UMDs responsibility to ensure the mapping is no longer in
> > use before
> > + * calling VM_UNBIND.
> > + *
> > + * If the specified mapping is not found, the ioctl will simply
> > return without
> > + * any error.
> > + *
> > + * VM_BIND/UNBIND ioctl calls executed on different CPU threads
> > concurrently
> > + * are not ordered. Furthermore, parts of the VM_UNBIND operation
> > can be done
> > + * asynchronously, if valid @fence is specified.
> > + */
> > +struct drm_i915_gem_vm_unbind {
> > + /** @vm_id: VM (address space) id to bind */
> > + __u32 vm_id;
> > +
> > + /** @rsvd: Reserved, MBZ */
> > + __u32 rsvd;
> > +
> > + /** @start: Virtual Address start to unbind */
> > + __u64 start;
> > +
> > + /** @length: Length of mapping to unbind */
> > + __u64 length;
> > +
> > + /** @flags: Currently reserved, MBZ */
> > + __u64 flags;
> > +
> > + /**
> > + * @fence: Timeline fence for unbind completion signaling.
> > + *
> > + * It is an out fence, hence using I915_TIMELINE_FENCE_WAIT
> flag
> > + * is invalid, and an error will be returned.
> > + */
> > + struct drm_i915_gem_timeline_fence fence;
> > +
> > + /**
> > + * @extensions: Zero-terminated chain of extensions.
> > + *
> > + * For future extensions. See struct i915_user_extension.
> > + */
> > + __u64 extensions;
> > +};
> > +
> > +/**
> > + * struct drm_i915_gem_execbuffer3 - Structure for
> > DRM_I915_GEM_EXECBUFFER3
> > + * ioctl.
> > + *
> > + * DRM_I915_GEM_EXECBUFFER3 ioctl only works in VM_BIND mode and
> > VM_BIND mode
> > + * only works with this ioctl for submission.
> > + * See I915_VM_CREATE_FLAGS_USE_VM_BIND.
> > + */
> > +struct drm_i915_gem_execbuffer3 {
> > + /**
> > + * @ctx_id: Context id
> > + *
> > + * Only contexts with user engine map are allowed.
> > + */
> > + __u32 ctx_id;
> > +
> > + /**
> > + * @engine_idx: Engine index
> > + *
> > + * An index in the user engine map of the context specified
> > by @ctx_id.
> > + */
> > + __u32 engine_idx;
> > +
> > + /**
> > + * @batch_address: Batch gpu virtual address/es.
> > + *
> > + * For normal submission, it is the gpu virtual address of
> > the batch
> > + * buffer. For parallel submission, it is a pointer to an
> > array of
> > + * batch buffer gpu virtual addresses with array size equal
> > to the
> > + * number of (parallel) engines involved in that submission
> (See
> > + * struct i915_context_engines_parallel_submit).
> > + */
> > + __u64 batch_address;
> > +
> > + /** @flags: Currently reserved, MBZ */
> > + __u64 flags;
> > +
> > + /** @rsvd1: Reserved, MBZ */
> > + __u32 rsvd1;
> > +
> > + /** @fence_count: Number of fences in @timeline_fences
> array. */
> > + __u32 fence_count;
> > +
> > + /**
> > + * @timeline_fences: Pointer to an array of timeline fences.
> > + *
> > + * Timeline fences are of format struct
> > drm_i915_gem_timeline_fence.
> > + */
> > + __u64 timeline_fences;
> > +
> > + /** @rsvd2: Reserved, MBZ */
> > + __u64 rsvd2;
> > +
> > + /**
> > + * @extensions: Zero-terminated chain of extensions.
> > + *
> > + * For future extensions. See struct i915_user_extension.
> > + */
> > + __u64 extensions;
> > +};
> > +
> > +/**
> > + * struct drm_i915_gem_create_ext_vm_private - Extension to make
> > the object
> > + * private to the specified VM.
> > + *
> > + * See struct drm_i915_gem_create_ext.
> > + */
> > +struct drm_i915_gem_create_ext_vm_private {
> > +#define I915_GEM_CREATE_EXT_VM_PRIVATE 2
> > + /** @base: Extension link. See struct i915_user_extension. */
> > + struct i915_user_extension base;
> > +
> > + /** @vm_id: Id of the VM to which the object is private */
> > + __u32 vm_id;
> > +};
> > --
> > 2.21.0.rc0.32.g243a4c7e27
> >
>
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