Re: [PATCH 3/3] drm/doc/rfc: VM_BIND uapi definition

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On 10/06/2022 13:37, Tvrtko Ursulin wrote:

On 10/06/2022 08:07, Niranjana Vishwanathapura wrote:
VM_BIND and related uapi definitions

Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@xxxxxxxxx>
---
  Documentation/gpu/rfc/i915_vm_bind.h | 490 +++++++++++++++++++++++++++
  1 file changed, 490 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..9fc854969cfb
--- /dev/null
+++ b/Documentation/gpu/rfc/i915_vm_bind.h
@@ -0,0 +1,490 @@
+/* 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.
+ * bit[0]: If set, VM_BIND is supported, otherwise not.
+ * bits[8-15]: VM_BIND implementation version.
+ * version 0 will not have VM_BIND/UNBIND timeline fence array support.
+ */
+#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.
+ *
+ * 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)
+
+/**
+ * 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_SIGNAL (See &drm_i915_gem_exec_fence.flags) is 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_EXECBUFFER3    0x3f
+#define DRM_I915_GEM_WAIT_USER_FENCE    0x40
+
+#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) +#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).
+ *
+ * The @queue_idx specifies the queue to use for binding. Same queue can be + * used for both VM_BIND and VM_UNBIND calls. All submitted bind and unbind
+ * operations in a queue are performed in the order of submission.
+ *
+ * The @start, @offset and @length should 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 should be 2M aligned, @offset and @length should be 64K aligned. + * Also, on those platforms, it is not allowed to bind an device local-memory + * object and a system memory object in a single 2M section of VA range.
+ */
+struct drm_i915_gem_vm_bind {
+    /** @vm_id: VM (address space) id to bind */
+    __u32 vm_id;
+
+    /** @queue_idx: Index of queue for binding */
+    __u32 queue_idx;

I have a question here to which I did not find an answer by browsing the old threads.

Queue index appears to be an implicit synchronisation mechanism, right? Operations on the same index are executed/complete in order of ioctl submission?

Do we _have_ to implement this on the kernel side and could just allow in/out fence and let userspace deal with it?


It orders operations like in a queue. Which is kind of what happens with existing queues/engines.

If I understood correctly, it's going to be a kthread + a linked list right?


-Lionel



Arbitrary/on-demand number of queues will add the complexity on the kernel side which should be avoided if possible.

Regards,

Tvrtko

+
+    /** @rsvd: Reserved, MBZ */
+    __u32 rsvd;
+
+    /** @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 << 0)
+#define I915_GEM_VM_BIND_CAPTURE     (1 << 1)
+
+    /**
+     * @extensions: 0-terminated chain of extensions for this operation.
+     *
+     * I915_VM_BIND_EXT_TIMELINE_FENCES:
+     * Specifies an array of input or output timeline fences for this
+     * binding operation. See struct drm_i915_vm_bind_ext_timeline_fences.
+     *
+     * I915_VM_BIND_EXT_USER_FENCES:
+     * Specifies an array of input or output user fences for this
+     * binding operation. See struct drm_i915_vm_bind_ext_user_fence.
+     * This is required for compute contexts.
+     */
+    __u64 extensions;
+#define I915_VM_BIND_EXT_TIMELINE_FENCES    0
+#define I915_VM_BIND_EXT_USER_FENCES        1
+};
+
+/**
+ * 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.
+ *
+ * The @queue_idx specifies the queue to use for unbinding.
+ * See struct drm_i915_gem_vm_unbind for more information on @queue_idx.
+ *
+ * The @start and @length musy specify a unique mapping bound with VM_BIND
+ * ioctl.
+ */
+struct drm_i915_gem_vm_unbind {
+    /** @vm_id: VM (address space) id to bind */
+    __u32 vm_id;
+
+    /** @queue_idx: Index of queue for unbinding */
+    __u32 queue_idx;
+
+    /** @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 operation.
+     *
+     * I915_VM_UNBIND_EXT_TIMELINE_FENCES:
+     * Specifies an array of input or output timeline fences for this
+     * unbind operation.
+     * It has same format as struct drm_i915_vm_bind_ext_timeline_fences.
+     *
+     * I915_VM_UNBIND_EXT_USER_FENCES:
+     * Specifies an array of input or output user fences for this
+     * unbind operation. This is required for compute contexts.
+     * It has same format as struct drm_i915_vm_bind_ext_user_fence.
+     */
+    __u64 extensions;
+#define I915_VM_UNBIND_EXT_TIMELINE_FENCES    0
+#define I915_VM_UNBIND_EXT_USER_FENCES        1
+};
+
+/**
+ * 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 {
+    /** @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 {
+    /** @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_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;
+
+    /** @rsvd1: Reserved, MBZ */
+    __u32 rsvd1;
+
+    /**
+     * @batch_count: Number of batches in @batch_address array.
+     *
+     * 0 is invalid. For parallel submission, it should be equal to the
+     * number of (parallel) engines involved in that submission.
+     */
+    __u32 batch_count;
+
+    /**
+     * @batch_address: Array of batch gpu virtual addresses.
+     *
+     * If @batch_count is 1, then it is the gpu virtual address of the
+     * batch buffer. If @batch_count > 1, then it is a pointer to an array
+     * of batch buffer gpu virtual addresses.
+     */
+    __u64 batch_address;
+
+    /**
+     * @flags: Supported flags are:
+     *
+     * I915_EXEC3_SECURE:
+     * Request a privileged ("secure") batch buffer/s.
+     * It is only available for DRM_ROOT_ONLY | DRM_MASTER processes.
+     */
+    __u64 flags;
+#define I915_EXEC3_SECURE    (1<<0)
+
+    /** @rsvd2: Reserved, MBZ */
+    __u64 rsvd2;
+
+    /**
+     * @extensions: Zero-terminated chain of extensions.
+     *
+     * DRM_I915_GEM_EXECBUFFER3_EXT_TIMELINE_FENCES:
+     * It has same format as DRM_I915_GEM_EXECBUFFER_EXT_TIMELINE_FENCES.
+     * See struct drm_i915_gem_execbuffer_ext_timeline_fences.
+     *
+     * DRM_I915_GEM_EXECBUFFER3_EXT_USER_FENCE:
+     * First level batch completion signaling extension.
+     * See struct drm_i915_gem_execbuffer3_ext_user_fence.
+     */
+    __u64 extensions;
+#define DRM_I915_GEM_EXECBUFFER3_EXT_TIMELINE_FENCES    0
+#define DRM_I915_GEM_EXECBUFFER3_EXT_USER_FENCE        1
+};
+
+/**
+ * struct drm_i915_gem_execbuffer3_ext_user_fence - First level batch completion
+ * signaling extension.
+ *
+ * This extension allows user to attach a user fence (@addr, @value pair) to + * execbuf3, 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_execbuffer3_ext_user_fence {
+    /** @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, 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;
+};





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