Re: [Intel-gfx] [RFC v3 3/3] drm/doc/rfc: VM_BIND uapi definition

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 17/05/2022 19:32, Niranjana Vishwanathapura wrote:
> VM_BIND and related uapi definitions
> 
> v2: Ensure proper kernel-doc formatting with cross references.
>      Also add new uapi and documentation as per review comments
>      from Daniel.
> 
> Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
> ---
>   Documentation/gpu/rfc/i915_vm_bind.h | 399 +++++++++++++++++++++++++++
>   1 file changed, 399 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..589c0a009107
> --- /dev/null
> +++ b/Documentation/gpu/rfc/i915_vm_bind.h
> @@ -0,0 +1,399 @@
> +/* SPDX-License-Identifier: MIT */
> +/*
> + * Copyright © 2022 Intel Corporation
> + */
> +
> +/**
> + * DOC: I915_PARAM_HAS_VM_BIND
> + *
> + * VM_BIND feature availability.
> + * See typedef drm_i915_getparam_t param.
> + */
> +#define I915_PARAM_HAS_VM_BIND		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.
> + *
> + * A VM in VM_BIND mode will not support the older execbuff mode of binding.
> + * In VM_BIND mode, execbuff ioctl will not accept any execlist (ie., the
> + * &drm_i915_gem_execbuffer2.buffer_count must be 0).
> + * Also, &drm_i915_gem_execbuffer2.batch_start_offset and
> + * &drm_i915_gem_execbuffer2.batch_len must be 0.
> + * DRM_I915_GEM_EXECBUFFER_EXT_BATCH_ADDRESSES extension must be provided
> + * to pass in the batch buffer addresses.
> + *
> + * Additionally, I915_EXEC_NO_RELOC, I915_EXEC_HANDLE_LUT and
> + * I915_EXEC_BATCH_FIRST of &drm_i915_gem_execbuffer2.flags must be 0
> + * (not used) in VM_BIND mode. I915_EXEC_USE_EXTENSIONS flag must always be
> + * set (See struct drm_i915_gem_execbuffer_ext_batch_addresses).
> + * The buffers_ptr, buffer_count, batch_start_offset and batch_len fields
> + * of struct drm_i915_gem_execbuffer2 are also not used and must be 0.
> + */
> +#define I915_VM_CREATE_FLAGS_USE_VM_BIND	(1 << 0)
> +
> +/**
> + * DOC: I915_CONTEXT_CREATE_FLAGS_LONG_RUNNING
> + *
> + * Flag to declare context as long running.
> + * See struct drm_i915_gem_context_create_ext flags.
> + *
> + * Usage of dma-fence expects that they complete in reasonable amount of time.
> + * Compute on the other hand can be long running. Hence it is not appropriate
> + * for compute contexts to export request completion dma-fence to user.
> + * The dma-fence usage will be limited to in-kernel consumption only.
> + * Compute contexts need to use user/memory fence.
> + *
> + * So, long running contexts do not support output fences. Hence,
> + * I915_EXEC_FENCE_OUT (See &drm_i915_gem_execbuffer2.flags and
> + * I915_EXEC_FENCE_SIGNAL (See &drm_i915_gem_exec_fence.flags) are expected
> + * to be not used.
> + *
> + * DRM_I915_GEM_WAIT ioctl call is also not supported for objects mapped
> + * to long running contexts.
> + */
> +#define I915_CONTEXT_CREATE_FLAGS_LONG_RUNNING   (1u << 2)
> +
> +/* VM_BIND related ioctls */
> +#define DRM_I915_GEM_VM_BIND		0x3d
> +#define DRM_I915_GEM_VM_UNBIND		0x3e
> +#define DRM_I915_GEM_WAIT_USER_FENCE	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_WAIT_USER_FENCE	DRM_IOWR(DRM_COMMAND_BASE + DRM_I915_GEM_WAIT_USER_FENCE, struct drm_i915_gem_wait_user_fence)
> +
> +/**
> + * 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).
> + */
> +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;

Does it support, or should it, equivalent of EXEC_OBJECT_PAD_TO_SIZE? Or 
if not userspace is expected to map the remainder of the space to a 
dummy object? In which case would there be any alignment/padding issues 
preventing the two bind to be placed next to each other?

I ask because someone from the compute side asked me about a problem 
with their strategy of dealing with overfetch and I suggested pad to size.

Regards,

Tvrtko

> +
> +	/**
> +	 * @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 << 0)
> +#define I915_GEM_VM_BIND_CAPTURE     (1 << 1)
> +
> +	/** @extensions: 0-terminated chain of extensions for this mapping. */
> +	__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). The specified VA range must match one of the
> + * mappings created with the VM_BIND ioctl. TLB is flushed upon unbind
> + * completion.
> + */
> +struct drm_i915_gem_vm_unbind {
> +	/** @vm_id: VM (address space) id to bind */
> +	__u32 vm_id;
> +
> +	/** @rsvd: Reserved for future use; must be zero. */
> +	__u32 rsvd;
> +
> +	/** @start: Virtual Address start to unbind */
> +	__u64 start;
> +
> +	/** @length: Length of mapping to unbind */
> +	__u64 length;
> +
> +	/** @flags: reserved for future usage, currently MBZ */
> +	__u64 flags;
> +
> +	/** @extensions: 0-terminated chain of extensions for this mapping. */
> +	__u64 extensions;
> +};
> +
> +/**
> + * struct drm_i915_vm_bind_fence - An input or output fence for the vm_bind
> + * or the vm_unbind work.
> + *
> + * The vm_bind or vm_unbind aync worker will wait for input fence to signal
> + * before starting the binding or unbinding.
> + *
> + * The vm_bind or vm_unbind async worker will signal the returned output fence
> + * after the completion of binding or unbinding.
> + */
> +struct drm_i915_vm_bind_fence {
> +	/** @handle: User's handle for a drm_syncobj to wait on or signal. */
> +	__u32 handle;
> +
> +	/**
> +	 * @flags: Supported flags are,
> +	 *
> +	 * I915_VM_BIND_FENCE_WAIT:
> +	 * Wait for the input fence before binding/unbinding
> +	 *
> +	 * I915_VM_BIND_FENCE_SIGNAL:
> +	 * Return bind/unbind completion fence as output
> +	 */
> +	__u32 flags;
> +#define I915_VM_BIND_FENCE_WAIT            (1<<0)
> +#define I915_VM_BIND_FENCE_SIGNAL          (1<<1)
> +#define __I915_VM_BIND_FENCE_UNKNOWN_FLAGS (-(I915_VM_BIND_FENCE_SIGNAL << 1))
> +};
> +
> +/**
> + * struct drm_i915_vm_bind_ext_timeline_fences - Timeline fences for vm_bind
> + * and vm_unbind.
> + *
> + * This structure describes an array of timeline drm_syncobj and associated
> + * points for timeline variants of drm_syncobj. These timeline 'drm_syncobj's
> + * can be input or output fences (See struct drm_i915_vm_bind_fence).
> + */
> +struct drm_i915_vm_bind_ext_timeline_fences {
> +#define I915_VM_BIND_EXT_timeline_FENCES	0
> +	/** @base: Extension link. See struct i915_user_extension. */
> +	struct i915_user_extension base;
> +
> +	/**
> +	 * @fence_count: Number of elements in the @handles_ptr & @value_ptr
> +	 * arrays.
> +	 */
> +	__u64 fence_count;
> +
> +	/**
> +	 * @handles_ptr: Pointer to an array of struct drm_i915_vm_bind_fence
> +	 * of length @fence_count.
> +	 */
> +	__u64 handles_ptr;
> +
> +	/**
> +	 * @values_ptr: Pointer to an array of u64 values of length
> +	 * @fence_count.
> +	 * Values 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 values_ptr;
> +};
> +
> +/**
> + * struct drm_i915_vm_bind_user_fence - An input or output user fence for the
> + * vm_bind or the vm_unbind work.
> + *
> + * The vm_bind or vm_unbind aync worker will wait for the input fence (value at
> + * @addr to become equal to @val) before starting the binding or unbinding.
> + *
> + * The vm_bind or vm_unbind async worker will signal the output fence after
> + * the completion of binding or unbinding by writing @val to memory location at
> + * @addr
> + */
> +struct drm_i915_vm_bind_user_fence {
> +	/** @addr: User/Memory fence qword aligned process virtual address */
> +	__u64 addr;
> +
> +	/** @val: User/Memory fence value to be written after bind completion */
> +	__u64 val;
> +
> +	/**
> +	 * @flags: Supported flags are,
> +	 *
> +	 * I915_VM_BIND_USER_FENCE_WAIT:
> +	 * Wait for the input fence before binding/unbinding
> +	 *
> +	 * I915_VM_BIND_USER_FENCE_SIGNAL:
> +	 * Return bind/unbind completion fence as output
> +	 */
> +	__u32 flags;
> +#define I915_VM_BIND_USER_FENCE_WAIT            (1<<0)
> +#define I915_VM_BIND_USER_FENCE_SIGNAL          (1<<1)
> +#define __I915_VM_BIND_USER_FENCE_UNKNOWN_FLAGS \
> +	(-(I915_VM_BIND_USER_FENCE_SIGNAL << 1))
> +};
> +
> +/**
> + * struct drm_i915_vm_bind_ext_user_fence - User/memory fences for vm_bind
> + * and vm_unbind.
> + *
> + * These user fences can be input or output fences
> + * (See struct drm_i915_vm_bind_user_fence).
> + */
> +struct drm_i915_vm_bind_ext_user_fence {
> +#define I915_VM_BIND_EXT_USER_FENCES	1
> +	/** @base: Extension link. See struct i915_user_extension. */
> +	struct i915_user_extension base;
> +
> +	/** @fence_count: Number of elements in the @user_fence_ptr array. */
> +	__u64 fence_count;
> +
> +	/**
> +	 * @user_fence_ptr: Pointer to an array of
> +	 * struct drm_i915_vm_bind_user_fence of length @fence_count.
> +	 */
> +	__u64 user_fence_ptr;
> +};
> +
> +/**
> + * struct drm_i915_gem_execbuffer_ext_batch_addresses - Array of batch buffer
> + * gpu virtual addresses.
> + *
> + * In the execbuff ioctl (See struct drm_i915_gem_execbuffer2), this extension
> + * must always be appended in the VM_BIND mode and it will be an error to
> + * append this extension in older non-VM_BIND mode.
> + */
> +struct drm_i915_gem_execbuffer_ext_batch_addresses {
> +#define DRM_I915_GEM_EXECBUFFER_EXT_BATCH_ADDRESSES	1
> +	/** @base: Extension link. See struct i915_user_extension. */
> +	struct i915_user_extension base;
> +
> +	/** @count: Number of addresses in the addr array. */
> +	__u32 count;
> +
> +	/** @addr: An array of batch gpu virtual addresses. */
> +	__u64 addr[0];
> +};
> +
> +/**
> + * struct drm_i915_gem_execbuffer_ext_user_fence - First level batch completion
> + * signaling extension.
> + *
> + * This extension allows user to attach a user fence (@addr, @value pair) to an
> + * execbuf to be signaled by the command streamer after the completion of first
> + * level batch, by writing the @value at specified @addr and triggering an
> + * interrupt.
> + * User can either poll for this user fence to signal or can also wait on it
> + * with i915_gem_wait_user_fence ioctl.
> + * This is very much usefaul for long running contexts where waiting on dma-fence
> + * by user (like i915_gem_wait ioctl) is not supported.
> + */
> +struct drm_i915_gem_execbuffer_ext_user_fence {
> +#define DRM_I915_GEM_EXECBUFFER_EXT_USER_FENCE		2
> +	/** @base: Extension link. See struct i915_user_extension. */
> +	struct i915_user_extension base;
> +
> +	/**
> +	 * @addr: User/Memory fence qword aligned GPU virtual address.
> +	 *
> +	 * Address has to be a valid GPU virtual address at the time of
> +	 * first level batch completion.
> +	 */
> +	__u64 addr;
> +
> +	/**
> +	 * @value: User/Memory fence Value to be written to above address
> +	 * after first level batch completes.
> +	 */
> +	__u64 value;
> +
> +	/** @rsvd: Reserved for future extensions, MBZ */
> +	__u64 rsvd;
> +};
> +
> +/**
> + * 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;
> +};
> +
> +/**
> + * struct drm_i915_gem_wait_user_fence - Wait on user/memory fence.
> + *
> + * User/Memory fence can be woken up either by:
> + *
> + * 1. GPU context indicated by @ctx_id, or,
> + * 2. Kerrnel driver async worker upon I915_UFENCE_WAIT_SOFT.
> + *    @ctx_id is ignored when this flag is set.
> + *
> + * Wakeup condition is,
> + * ``((*addr & mask) op (value & mask))``
> + *
> + * See :ref:`Documentation/driver-api/dma-buf.rst <indefinite_dma_fences>`
> + */
> +struct drm_i915_gem_wait_user_fence {
> +	/** @extensions: Zero-terminated chain of extensions. */
> +	__u64 extensions;
> +
> +	/** @addr: User/Memory fence address */
> +	__u64 addr;
> +
> +	/** @ctx_id: Id of the Context which will signal the fence. */
> +	__u32 ctx_id;
> +
> +	/** @op: Wakeup condition operator */
> +	__u16 op;
> +#define I915_UFENCE_WAIT_EQ      0
> +#define I915_UFENCE_WAIT_NEQ     1
> +#define I915_UFENCE_WAIT_GT      2
> +#define I915_UFENCE_WAIT_GTE     3
> +#define I915_UFENCE_WAIT_LT      4
> +#define I915_UFENCE_WAIT_LTE     5
> +#define I915_UFENCE_WAIT_BEFORE  6
> +#define I915_UFENCE_WAIT_AFTER   7
> +
> +	/**
> +	 * @flags: Supported flags are,
> +	 *
> +	 * I915_UFENCE_WAIT_SOFT:
> +	 *
> +	 * To be woken up by i915 driver async worker (not by GPU).
> +	 *
> +	 * I915_UFENCE_WAIT_ABSTIME:
> +	 *
> +	 * Wait timeout specified as absolute time.
> +	 */
> +	__u16 flags;
> +#define I915_UFENCE_WAIT_SOFT    0x1
> +#define I915_UFENCE_WAIT_ABSTIME 0x2
> +
> +	/** @value: Wakeup value */
> +	__u64 value;
> +
> +	/** @mask: Wakeup mask */
> +	__u64 mask;
> +#define I915_UFENCE_WAIT_U8     0xffu
> +#define I915_UFENCE_WAIT_U16    0xffffu
> +#define I915_UFENCE_WAIT_U32    0xfffffffful
> +#define I915_UFENCE_WAIT_U64    0xffffffffffffffffull
> +
> +	/**
> +	 * @timeout: Wait timeout in nanoseconds.
> +	 *
> +	 * If I915_UFENCE_WAIT_ABSTIME flag is set, then time timeout is the
> +	 * absolute time in nsec.
> +	 */
> +	__s64 timeout;
> +};