open-gpu-kernel-modules/kernel-open/nvidia-uvm/uvm_channel.h

/*******************************************************************************
    Copyright (c) 2015-2023 NVIDIA Corporation

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#ifndef __UVM_CHANNEL_H__
#define __UVM_CHANNEL_H__

#include "nv_uvm_types.h"
#include "uvm_forward_decl.h"
#include "uvm_gpu_semaphore.h"
#include "uvm_pushbuffer.h"
#include "uvm_tracker.h"

//
// UVM channels
//
// A channel manager is created as part of the GPU addition. This involves
// creating channels for each of the supported types (uvm_channel_type_t) in
// separate channel pools possibly using different CE instances in the HW. Each
// channel has a uvm_gpu_tracking_semaphore_t and a set of uvm_gpfifo_entry_t
// (one per each HW GPFIFO entry) allowing to track completion of pushes on the
// channel.
//
// Beginning a push on a channel implies reserving a GPFIFO entry in that
// channel and hence there can only be as many on-going pushes per channel as
// there are free GPFIFO entries. This ensures that ending a push won't have to
// wait for a GPFIFO entry to free up.
//

#define UVM_CHANNEL_NUM_GPFIFO_ENTRIES_DEFAULT 1024
#define UVM_CHANNEL_NUM_GPFIFO_ENTRIES_MIN 32
#define UVM_CHANNEL_NUM_GPFIFO_ENTRIES_MAX (1024 * 1024)

// Maximum number of channels per pool.
#define UVM_CHANNEL_MAX_NUM_CHANNELS_PER_POOL UVM_PUSH_MAX_CONCURRENT_PUSHES

// Semaphore payloads cannot advance too much between calls to
// uvm_gpu_tracking_semaphore_update_completed_value(). In practice the jumps
// are bound by gpfifo sizing as we have to update the completed value to
// reclaim gpfifo entries. Set a limit based on the max gpfifo entries we could
// ever see.
//
// Logically this define belongs to uvm_gpu_semaphore.h but it depends on the
// channel GPFIFO sizing defined here so it's easiest to just have it here as
// uvm_channel.h includes uvm_gpu_semaphore.h.
#define UVM_GPU_SEMAPHORE_MAX_JUMP (2 * UVM_CHANNEL_NUM_GPFIFO_ENTRIES_MAX)

#define uvm_channel_pool_assert_locked(pool) (          \
{                                                       \
    if (uvm_channel_pool_uses_mutex(pool))              \
        uvm_assert_mutex_locked(&(pool)->mutex);        \
    else                                                \
        uvm_assert_spinlock_locked(&(pool)->spinlock);  \
})

// Channel types
typedef enum
{
    // CPU to GPU copies
    UVM_CHANNEL_TYPE_CPU_TO_GPU,

    // GPU to CPU copies
    UVM_CHANNEL_TYPE_GPU_TO_CPU,

    // Memsets and copies within the GPU
    UVM_CHANNEL_TYPE_GPU_INTERNAL,

    // Memops and small memsets/copies for writing PTEs
    UVM_CHANNEL_TYPE_MEMOPS,

    // GPU to GPU peer copies
    UVM_CHANNEL_TYPE_GPU_TO_GPU,

    UVM_CHANNEL_TYPE_CE_COUNT,

    // ^^^^^^
    // Channel types backed by a CE.
    // ----------------------------------
    // Channel types not backed by a CE.
    // vvvvvv

    // SEC2 channels
    UVM_CHANNEL_TYPE_SEC2 = UVM_CHANNEL_TYPE_CE_COUNT,

    // ----------------------------------
    // Channel type with fixed schedules

    // Work Launch Channel (WLC) is a specialized channel for launching work on
    // other channels when the Confidential Computing is feature enabled. It is
    // paired with LCIC (below)
    UVM_CHANNEL_TYPE_WLC,

    // Launch Confirmation Indicator Channel (LCIC) is a specialized channel
    // with fixed schedule. It gets triggered by executing WLC work, and makes
    // sure that WLC get/put pointers are up-to-date.
    UVM_CHANNEL_TYPE_LCIC,

    UVM_CHANNEL_TYPE_COUNT,
} uvm_channel_type_t;

typedef enum
{
    // A pool that contains CE channels owned by UVM.
    UVM_CHANNEL_POOL_TYPE_CE = (1 << 0),

    // A proxy pool contains only proxy channels, so it only exists in SR-IOV
    // heavy. The pool is only used for UVM_CHANNEL_TYPE_MEMOPS pushes.
    //
    // A proxy channel is a privileged CE channel owned by the vGPU plugin. A
    // proxy channel cannot be manipulated directly by the UVM driver, who
    // instead can only submit work to it by invoking an RM API.
    //
    // There is a single proxy pool and channel per GPU.
    UVM_CHANNEL_POOL_TYPE_CE_PROXY = (1 << 1),

    // A pool of SEC2 channels owned by UVM. These channels are backed by a SEC2
    // engine.
    UVM_CHANNEL_POOL_TYPE_SEC2 = (1 << 2),

    UVM_CHANNEL_POOL_TYPE_WLC = (1 << 3),

    UVM_CHANNEL_POOL_TYPE_LCIC = (1 << 4),

    UVM_CHANNEL_POOL_TYPE_COUNT = 5,

    // A mask used to select pools of any type.
    UVM_CHANNEL_POOL_TYPE_MASK  = ((1U << UVM_CHANNEL_POOL_TYPE_COUNT) - 1)
} uvm_channel_pool_type_t;

typedef enum
{
    // Push-based GPFIFO entry
    UVM_GPFIFO_ENTRY_TYPE_NORMAL,

    // Control GPFIFO entry, i.e., the LENGTH field is zero, not associated with
    // a push.
    UVM_GPFIFO_ENTRY_TYPE_CONTROL
} uvm_gpfifo_entry_type_t;

struct uvm_gpfifo_entry_struct
{
    uvm_gpfifo_entry_type_t type;

    // Channel tracking semaphore value that indicates completion of
    // this entry.
    NvU64 tracking_semaphore_value;

    union {
        struct {
            // Offset of the pushbuffer in the pushbuffer allocation used by
            // this entry.
            NvU32 pushbuffer_offset;

            // Size of the pushbuffer used for this entry.
            NvU32 pushbuffer_size;
        };

        // Value of control entry
        // Exact value of GPFIFO entry copied directly to GPFIFO[PUT] location.
        NvU64 control_value;
    };

    // The following fields are only valid when type is
    // UVM_GPFIFO_ENTRY_TYPE_NORMAL.

    // List node used by the pushbuffer tracking
    struct list_head pending_list_node;

    // Push info for the pending push that used this GPFIFO entry
    uvm_push_info_t *push_info;
};

// A channel pool is a set of channels that use the same engine. For example,
// all channels in a CE pool share the same (logical) Copy Engine.
typedef struct
{
    // Owning channel manager
    uvm_channel_manager_t *manager;

    // On Volta+ GPUs, all channels in a pool are members of the same TSG, i.e.,
    // num_tsgs is 1. Pre-Volta GPUs also have a single TSG object, but since HW
    // does not support TSG for CE engines, a HW TSG is not created, but a TSG
    // object is required to allocate channels.
    // When Confidential Computing mode is enabled, the WLC and LCIC channel
    // types require one TSG for each WLC/LCIC pair of channels. In this case,
    // we do not use a TSG per channel pool, but instead a TSG per WLC/LCIC
    // channel pair, num_tsgs equals to the number of channel pairs.
    uvmGpuTsgHandle *tsg_handles;

    // Number TSG handles owned by this pool.
    NvU32 num_tsgs;

    // Channels in this pool
    uvm_channel_t *channels;

    // Number of elements in the channel array
    NvU32 num_channels;

    // Index of the engine associated with the pool (index is an offset from the
    // first engine of the same engine type.)
    unsigned engine_index;

    // Pool type: Refer to the uvm_channel_pool_type_t enum.
    uvm_channel_pool_type_t pool_type;

    // Lock protecting the state of channels in the pool.
    //
    // There are two pool lock types available: spinlock and mutex. The mutex
    // variant is required when the thread holding the pool lock must sleep
    // (ex: acquire another mutex) deeper in the call stack, either in UVM or
    // RM.
    union {
        uvm_spinlock_t spinlock;
        uvm_mutex_t mutex;
    };

    // Secure operations require that uvm_push_begin order matches
    // uvm_push_end order, because the engine's state is used in its internal
    // operation and each push may modify this state. push_locks is protected by
    // the channel pool lock.
    DECLARE_BITMAP(push_locks, UVM_CHANNEL_MAX_NUM_CHANNELS_PER_POOL);

    // Counting semaphore for available and unlocked channels, it must be
    // acquired before submitting work to a channel when the Confidential
    // Computing feature is enabled.
    uvm_semaphore_t push_sem;
} uvm_channel_pool_t;

struct uvm_channel_struct
{
    // Owning pool
    uvm_channel_pool_t *pool;

    // The channel name contains the CE index, and (for UVM internal channels)
    // the HW runlist and channel IDs.
    char name[64];

    // Array of gpfifo entries, one per each HW GPFIFO
    uvm_gpfifo_entry_t *gpfifo_entries;

    // Number of GPFIFO entries in gpfifo_entries
    NvU32 num_gpfifo_entries;

    // Latest GPFIFO entry submitted to the GPU
    // Updated when new pushes are submitted to the GPU in
    // uvm_channel_end_push().
    NvU32 cpu_put;

    // Latest GPFIFO entry completed by the GPU
    // Updated by uvm_channel_update_progress() after checking pending GPFIFOs
    // for completion.
    NvU32 gpu_get;

    // Number of currently on-going gpfifo entries on this channel
    // A new push or control GPFIFO is only allowed to begin on the channel if
    // there is a free GPFIFO entry for it.
    NvU32 current_gpfifo_count;

    // Array of uvm_push_info_t for all pending pushes on the channel
    uvm_push_info_t *push_infos;

    // Array of uvm_push_acquire_info_t for all pending pushes on the channel.
    // Each entry corresponds to the push_infos entry with the same index.
    uvm_push_acquire_info_t *push_acquire_infos;

    // List of uvm_push_info_entry_t that are currently available. A push info
    // entry is not available if it has been assigned to a push
    // (uvm_push_begin), and the GPFIFO entry associated with the push has not
    // been marked as completed.
    struct list_head available_push_infos;

    // GPU tracking semaphore tracking the work in the channel.
    // Each push on the channel increments the semaphore, see
    // uvm_channel_end_push().
    uvm_gpu_tracking_semaphore_t tracking_sem;

    struct
    {
        // Secure operations require that uvm_push_begin order matches
        // uvm_push_end order, because the engine's state is used in
        // its internal operation and each push may modify this state.
        uvm_mutex_t push_lock;

        // When the Confidential Computing feature is enabled, every channel has
        // cryptographic state in HW, which is mirrored here for CPU-side
        // operations.
        UvmCslContext ctx;
        bool is_ctx_initialized;

        // CPU-side CSL crypto operations which operate on the same CSL state
        // are not thread-safe, so they must be wrapped in locks at the UVM
        // level. Encryption, decryption and logging operations must be
        // protected with the ctx_lock.
        uvm_mutex_t ctx_lock;
    } csl;

    struct
    {
        // The value of GPU side PUT index.
        // Indirect work submission introduces delay between updating the CPU
        // put when ending a push, and updating the GPU visible value via
        // indirect work launch. It is used to order multiple pending indirect
        // work launches to match the order of push end-s that triggered them.
        volatile NvU32 gpu_put;

        // Static pushbuffer for channels with static schedule (WLC/LCIC)
        uvm_rm_mem_t *static_pb_protected_vidmem;

        // Static pushbuffer staging buffer for WLC
        uvm_rm_mem_t *static_pb_unprotected_sysmem;
        void *static_pb_unprotected_sysmem_cpu;
        void *static_pb_unprotected_sysmem_auth_tag_cpu;

        // The above static locations are required by the WLC (and LCIC)
        // schedule. Protected sysmem location completes WLC's independence
        // from the pushbuffer allocator.
        void *static_pb_protected_sysmem;

        // Static tracking semaphore notifier values
        // Because of LCIC's fixed schedule, the secure semaphore release
        // mechanism uses two additional static locations for incrementing the
        // notifier values. See:
        // . channel_semaphore_secure_release()
        // . setup_lcic_schedule()
        // . internal_channel_submit_work_wlc()
        uvm_rm_mem_t *static_notifier_unprotected_sysmem;
        NvU32 *static_notifier_entry_unprotected_sysmem_cpu;
        NvU32 *static_notifier_exit_unprotected_sysmem_cpu;
        uvm_gpu_address_t static_notifier_entry_unprotected_sysmem_gpu_va;
        uvm_gpu_address_t static_notifier_exit_unprotected_sysmem_gpu_va;

        // Explicit location for push launch tag used by WLC.
        // Encryption auth tags have to be located in unprotected sysmem.
        void *launch_auth_tag_cpu;
        NvU64 launch_auth_tag_gpu_va;

        // Used to decrypt the push back to protected sysmem.
        // This happens when profilers register callbacks for migration data.
        uvm_push_crypto_bundle_t *push_crypto_bundles;

        // Accompanying authentication tags for the crypto bundles
        uvm_rm_mem_t *push_crypto_bundle_auth_tags;
    } conf_computing;

    // RM channel information
    union
    {
        // UVM internal channels
        struct
        {
            // UVM-RM interface handle
            uvmGpuChannelHandle handle;

            // Channel state populated by RM. Includes the GPFIFO, error
            // notifier, work submission information etc.
            UvmGpuChannelInfo channel_info;
        };

        // Proxy channels (SR-IOV heavy only)
        struct
        {
            // UVM-RM interface handle
            UvmGpuPagingChannelHandle handle;

            // Channel state populated by RM. Includes the error notifier.
            UvmGpuPagingChannelInfo channel_info;
        } proxy;
    };

    struct
    {
        struct proc_dir_entry *dir;
        struct proc_dir_entry *info;
        struct proc_dir_entry *pushes;
    } procfs;

    // Information managed by the tools event notification mechanism. Mainly
    // used to keep a list of channels with pending events, which is needed
    // to collect the timestamps of asynchronous operations.
    struct
    {
        struct list_head channel_list_node;
        NvU32 pending_event_count;
    } tools;
};

struct uvm_channel_manager_struct
{
    // The owning GPU
    uvm_gpu_t *gpu;

    // The pushbuffer used for all pushes done with this channel manager
    uvm_pushbuffer_t *pushbuffer;

    // Array of channel pools.
    uvm_channel_pool_t *channel_pools;

    // Number of elements in the pool array
    unsigned num_channel_pools;

    // Mask containing the indexes of the usable Copy Engines. Each usable CE
    // has at least one pool associated with it.
    DECLARE_BITMAP(ce_mask, UVM_COPY_ENGINE_COUNT_MAX);

    struct
    {
        // Pools to be used by each channel type by default.
        //
        // Transfers of a given type may use a pool different from that in
        // default_for_type[type]. For example, transfers to NvLink GPU
        // peers may instead use the more optimal pool stored in the gpu_to_gpu
        // array
        uvm_channel_pool_t *default_for_type[UVM_CHANNEL_TYPE_COUNT];

        // Optimal pools to use when writing from the owning GPU to its NvLink
        // peers.
        // If there is no optimal pool (the entry is NULL), use default pool
        // default_for_type[UVM_CHANNEL_GPU_TO_GPU] instead.
        uvm_channel_pool_t *gpu_to_gpu[UVM_ID_MAX_GPUS];
    } pool_to_use;

    struct
    {
        struct proc_dir_entry *channels_dir;
        struct proc_dir_entry *pending_pushes;
    } procfs;

    struct
    {
        NvU32 num_gpfifo_entries;
        UVM_BUFFER_LOCATION gpfifo_loc;
        UVM_BUFFER_LOCATION gpput_loc;
        UVM_BUFFER_LOCATION pushbuffer_loc;
    } conf;
};

// Create a channel manager for the GPU
NV_STATUS uvm_channel_manager_create(uvm_gpu_t *gpu, uvm_channel_manager_t **manager_out);

static bool uvm_pool_type_is_valid(uvm_channel_pool_type_t pool_type)
{
    return (is_power_of_2(pool_type) && (pool_type < UVM_CHANNEL_POOL_TYPE_MASK));
}

static bool uvm_channel_pool_is_sec2(uvm_channel_pool_t *pool)
{
    UVM_ASSERT(uvm_pool_type_is_valid(pool->pool_type));

    return (pool->pool_type == UVM_CHANNEL_POOL_TYPE_SEC2);
}

static bool uvm_channel_pool_is_wlc(uvm_channel_pool_t *pool)
{
    UVM_ASSERT(uvm_pool_type_is_valid(pool->pool_type));

    return (pool->pool_type == UVM_CHANNEL_POOL_TYPE_WLC);
}

static bool uvm_channel_pool_is_lcic(uvm_channel_pool_t *pool)
{
    UVM_ASSERT(uvm_pool_type_is_valid(pool->pool_type));

    return (pool->pool_type == UVM_CHANNEL_POOL_TYPE_LCIC);
}

static bool uvm_channel_is_sec2(uvm_channel_t *channel)
{
    return uvm_channel_pool_is_sec2(channel->pool);
}

static bool uvm_channel_is_wlc(uvm_channel_t *channel)
{
    return uvm_channel_pool_is_wlc(channel->pool);
}

static bool uvm_channel_is_lcic(uvm_channel_t *channel)
{
    return uvm_channel_pool_is_lcic(channel->pool);
}

static bool uvm_channel_pool_is_proxy(uvm_channel_pool_t *pool)
{
    UVM_ASSERT(uvm_pool_type_is_valid(pool->pool_type));

    return pool->pool_type == UVM_CHANNEL_POOL_TYPE_CE_PROXY;
}

static bool uvm_channel_is_proxy(uvm_channel_t *channel)
{
    return uvm_channel_pool_is_proxy(channel->pool);
}

static bool uvm_channel_pool_is_ce(uvm_channel_pool_t *pool)
{
    return !uvm_channel_pool_is_sec2(pool);
}

static bool uvm_channel_is_ce(uvm_channel_t *channel)
{
    return uvm_channel_pool_is_ce(channel->pool);
}

bool uvm_channel_pool_uses_mutex(uvm_channel_pool_t *pool);

// Proxy channels are used to push page tree related methods, so their channel
// type is UVM_CHANNEL_TYPE_MEMOPS.
static uvm_channel_type_t uvm_channel_proxy_channel_type(void)
{
    return UVM_CHANNEL_TYPE_MEMOPS;
}

// Privileged channels support all the Host and engine methods, while
// non-privileged channels don't support privileged methods.
//
// A major limitation of non-privileged CE channels is lack of physical
// addressing support.
bool uvm_channel_is_privileged(uvm_channel_t *channel);

// Destroy the channel manager
void uvm_channel_manager_destroy(uvm_channel_manager_t *channel_manager);

// Get the current status of the channel
// Returns NV_OK if the channel is in a good state and NV_ERR_RC_ERROR
// otherwise. Notably this never sets the global fatal error.
NV_STATUS uvm_channel_get_status(uvm_channel_t *channel);

// Check for channel errors
// Checks for channel errors by calling uvm_channel_get_status(). If an error
// occurred, sets the global fatal error and prints errors.
NV_STATUS uvm_channel_check_errors(uvm_channel_t *channel);

// Check errors on all channels in the channel manager
// Also includes uvm_global_get_status
NV_STATUS uvm_channel_manager_check_errors(uvm_channel_manager_t *channel_manager);

// Retrieve the GPFIFO entry that caused a channel error
// The channel has to be in error state prior to calling this function.
uvm_gpfifo_entry_t *uvm_channel_get_fatal_entry(uvm_channel_t *channel);

// Update progress of a specific channel
// Returns the number of still pending GPFIFO entries for that channel.
// Notably some of the pending GPFIFO entries might be already completed, but
// the update early-outs after completing a fixed number of them to spread the
// cost of the updates across calls.
NvU32 uvm_channel_update_progress(uvm_channel_t *channel);

// Update progress of all channels
// Returns the number of still pending GPFIFO entries for all channels.
// Notably some of the pending GPFIFO entries might be already completed, but
// the update early-outs after completing a fixed number of them to spread the
// cost of the updates across calls.
NvU32 uvm_channel_manager_update_progress(uvm_channel_manager_t *channel_manager);

// Wait for all channels to idle
// It waits for anything that is running, but doesn't prevent new work from
// beginning.
NV_STATUS uvm_channel_manager_wait(uvm_channel_manager_t *manager);

// Check if WLC/LCIC mechanism is ready/setup
// Should only return false during initialization
static bool uvm_channel_manager_is_wlc_ready(uvm_channel_manager_t *manager)
{
    return (manager->pool_to_use.default_for_type[UVM_CHANNEL_TYPE_WLC] != NULL) &&
           (manager->pool_to_use.default_for_type[UVM_CHANNEL_TYPE_LCIC] != NULL);
}
// Get the GPU VA of semaphore_channel's tracking semaphore within the VA space
// associated with access_channel.
//
// The channels can belong to different GPUs, the same GPU, or even be
// identical, in which case uvm_channel_tracking_semaphore_get_gpu_va can be
// used instead.
NvU64 uvm_channel_tracking_semaphore_get_gpu_va_in_channel(uvm_channel_t *semaphore_channel,
                                                           uvm_channel_t *access_channel);

// See above.
static NvU64 uvm_channel_tracking_semaphore_get_gpu_va(uvm_channel_t *channel)
{
    return uvm_channel_tracking_semaphore_get_gpu_va_in_channel(channel, channel);
}

// Check whether the channel completed a value
bool uvm_channel_is_value_completed(uvm_channel_t *channel, NvU64 value);

// Update and get the latest completed value by the channel
NvU64 uvm_channel_update_completed_value(uvm_channel_t *channel);

// Select and reserve a channel with the specified type for a push
NV_STATUS uvm_channel_reserve_type(uvm_channel_manager_t *manager,
                                   uvm_channel_type_t type,
                                   uvm_channel_t **channel_out);

// Select and reserve a channel for a transfer from channel_manager->gpu to
// dst_gpu.
NV_STATUS uvm_channel_reserve_gpu_to_gpu(uvm_channel_manager_t *channel_manager,
                                         uvm_gpu_t *dst_gpu,
                                         uvm_channel_t **channel_out);

// Reserve a specific channel for a push or for a control GPFIFO entry.
NV_STATUS uvm_channel_reserve(uvm_channel_t *channel, NvU32 num_gpfifo_entries);

// Set optimal CE for P2P transfers between manager->gpu and peer
void uvm_channel_manager_set_p2p_ce(uvm_channel_manager_t *manager, uvm_gpu_t *peer, NvU32 optimal_ce);

// Begin a push on a previously reserved channel
// Should be used by uvm_push_*() only.
NV_STATUS uvm_channel_begin_push(uvm_channel_t *channel, uvm_push_t *push);

// End a push
// Should be used by uvm_push_end() only.
void uvm_channel_end_push(uvm_push_t *push);

// Write/send a control GPFIFO to channel. This is not supported by proxy
// channels.
// Ordering guarantees:
// Input: Control GPFIFO entries are guaranteed to be processed by ESCHED after
// all prior GPFIFO entries and pushbuffers have been fetched, but not
// necessarily completed.
// Output ordering: A caller can wait for this control entry to complete with
// uvm_channel_manager_wait(), or by waiting for any later push in the same
// channel to complete.
NV_STATUS uvm_channel_write_ctrl_gpfifo(uvm_channel_t *channel, NvU64 ctrl_fifo_entry_value);

const char *uvm_channel_type_to_string(uvm_channel_type_t channel_type);
const char *uvm_channel_pool_type_to_string(uvm_channel_pool_type_t channel_pool_type);

// Returns the number of available GPFIFO entries. The function internally
// acquires the channel pool lock.
NvU32 uvm_channel_get_available_gpfifo_entries(uvm_channel_t *channel);

void uvm_channel_print_pending_pushes(uvm_channel_t *channel);

static uvm_gpu_t *uvm_channel_get_gpu(uvm_channel_t *channel)
{
    return channel->pool->manager->gpu;
}

static uvm_pushbuffer_t *uvm_channel_get_pushbuffer(uvm_channel_t *channel)
{
    return channel->pool->manager->pushbuffer;
}

// Index of a channel within the owning pool
static unsigned uvm_channel_index_in_pool(const uvm_channel_t *channel)
{
    return channel - channel->pool->channels;
}

NvU32 uvm_channel_update_progress_all(uvm_channel_t *channel);

// Return an arbitrary channel of the given type(s)
uvm_channel_t *uvm_channel_any_of_type(uvm_channel_manager_t *manager, NvU32 pool_type_mask);

// Return an arbitrary channel of any type
static uvm_channel_t *uvm_channel_any(uvm_channel_manager_t *manager)
{
    return uvm_channel_any_of_type(manager, UVM_CHANNEL_POOL_TYPE_MASK);
}

// Helper to iterate over all the channels in a pool.
#define uvm_for_each_channel_in_pool(channel, pool)                            \
    for (({UVM_ASSERT(pool->channels);                                         \
         channel = pool->channels;});                                          \
         channel != pool->channels + pool->num_channels;                       \
         channel++)

uvm_channel_pool_t *uvm_channel_pool_first(uvm_channel_manager_t *manager, NvU32 pool_type_mask);
uvm_channel_pool_t *uvm_channel_pool_next(uvm_channel_manager_t *manager,
                                          uvm_channel_pool_t *curr_pool,
                                          NvU32 pool_type_mask);

// Helper to iterate over all the channel pools of the given type(s) in a GPU.
// The pool mask must not be zero.
#define uvm_for_each_pool_of_type(pool, manager, pool_type_mask)               \
    for (pool = uvm_channel_pool_first(manager, pool_type_mask);               \
         pool != NULL;                                                         \
         pool = uvm_channel_pool_next(manager, pool, pool_type_mask))

#define uvm_for_each_pool(pool, manager) uvm_for_each_pool_of_type(pool, manager, UVM_CHANNEL_POOL_TYPE_MASK)

#endif // __UVM_CHANNEL_H__