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

[Lionel Landwerlin <lionel.g.landwerlin@intel.com>]

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@intel.com>
>> ---
>>   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;
>> +};