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

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    Copyright (c) 2015-2022 NVIDIA Corporation

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#ifndef __UVM_GPU_H__
#define __UVM_GPU_H__

#include "nvtypes.h"
#include "nvmisc.h"
#include "uvm_types.h"
#include "nv_uvm_types.h"
#include "uvm_linux.h"
#include "nv-kref.h"
#include "uvm_common.h"
#include "ctrl2080mc.h"
#include "uvm_forward_decl.h"
#include "uvm_processors.h"
#include "uvm_pmm_gpu.h"
#include "uvm_pmm_sysmem.h"
#include "uvm_mmu.h"
#include "uvm_gpu_replayable_faults.h"
#include "uvm_gpu_isr.h"
#include "uvm_hal_types.h"
#include "uvm_hmm.h"
#include "uvm_va_block_types.h"
#include "uvm_perf_module.h"
#include "uvm_rb_tree.h"
#include "nv-kthread-q.h"




// Buffer length to store uvm gpu id, RM device name and gpu uuid.
#define UVM_GPU_NICE_NAME_BUFFER_LENGTH (sizeof("ID 999: : ") + \
            UVM_GPU_NAME_LENGTH + UVM_GPU_UUID_TEXT_BUFFER_LENGTH)

#define UVM_GPU_MAGIC_VALUE 0xc001d00d12341993ULL

typedef struct
{
    // Number of faults from this uTLB that have been fetched but have not been serviced yet
    NvU32 num_pending_faults;

    // Whether the uTLB contains fatal faults
    bool has_fatal_faults;

    // We have issued a replay of type START_ACK_ALL while containing fatal faults. This puts
    // the uTLB in lockdown mode and no new translations are accepted
    bool in_lockdown;

    // We have issued a cancel on this uTLB
    bool cancelled;

    uvm_fault_buffer_entry_t prev_fatal_fault;

    // Last fetched fault that was originated from this uTLB. Used for fault
    // filtering.
    uvm_fault_buffer_entry_t *last_fault;
} uvm_fault_utlb_info_t;

struct uvm_service_block_context_struct
{
    //
    // Fields initialized by CPU/GPU fault handling and access counter routines
    //

    // Whether the information refers to replayable/non-replayable faults or
    // access counters
    uvm_service_operation_t operation;

    // Processors that will be the residency of pages after the operation has
    // been serviced
    uvm_processor_mask_t resident_processors;

    // VA block region that contains all the pages affected by the operation
    uvm_va_block_region_t region;

    // Array of type uvm_fault_access_type_t that contains the type of the
    // access that caused the fault/access_counter notification to be serviced
    // for each page.
    NvU8 access_type[PAGES_PER_UVM_VA_BLOCK];

    // Number of times the service operation has been retried
    unsigned num_retries;

    // Pages that need to be pinned due to thrashing
    uvm_page_mask_t thrashing_pin_mask;

    // Number of pages that need to be pinned due to thrashing. This is the same
    // value as the result of bitmap_weight(thrashing_pin_mask)
    unsigned thrashing_pin_count;

    // Pages that can be read-duplicated
    uvm_page_mask_t read_duplicate_mask;

    // Number of pages that can be read-duplicated. This is the same value as
    // the result of bitmap_weight(read_duplicate_count_mask)
    unsigned read_duplicate_count;

    //
    // Fields used by the CPU fault handling routine
    //

    struct
    {
        // Node of the list of fault service contexts used by the CPU
        struct list_head service_context_list;

        // A mask of GPUs that need to be checked for ECC errors before the CPU
        // fault handler returns, but after the VA space lock has been unlocked to
        // avoid the RM/UVM VA space lock deadlocks.
        uvm_processor_mask_t gpus_to_check_for_ecc;

        // This is set to throttle page fault thrashing.
        NvU64 wakeup_time_stamp;

        // This is set if the page migrated to/from the GPU and CPU.
        bool did_migrate;
    } cpu_fault;

    //
    // Fields managed by the common operation servicing routine
    //

    uvm_prot_page_mask_array_t mappings_by_prot;

    // Mask with the pages that did not migrate to the processor (they were
    // already resident) in the last call to uvm_va_block_make_resident.
    // This is used to compute the pages that need to revoke mapping permissions
    // from other processors.
    uvm_page_mask_t did_not_migrate_mask;

    // Pages whose permissions need to be revoked from other processors
    uvm_page_mask_t revocation_mask;

    struct
    {
        // Per-processor mask with the pages that will be resident after servicing.
        // We need one mask per processor because we may coalesce faults that
        // trigger migrations to different processors.
        uvm_page_mask_t new_residency;
    } per_processor_masks[UVM_ID_MAX_PROCESSORS];

    // State used by the VA block routines called by the servicing routine
    uvm_va_block_context_t block_context;
};

struct uvm_fault_service_batch_context_struct
{
    // Array of elements fetched from the GPU fault buffer. The number of
    // elements in this array is exactly max_batch_size
    uvm_fault_buffer_entry_t *fault_cache;

    // Array of pointers to elements in fault cache used for fault
    // preprocessing. The number of elements in this array is exactly
    // max_batch_size
    uvm_fault_buffer_entry_t **ordered_fault_cache;

    // Per uTLB fault information. Used for replay policies and fault
    // cancellation on Pascal
    uvm_fault_utlb_info_t *utlbs;

    // Largest uTLB id seen in a GPU fault
    NvU32 max_utlb_id;

    NvU32 num_cached_faults;

    NvU32 num_coalesced_faults;

    bool has_fatal_faults;

    bool has_throttled_faults;

    NvU32 num_invalid_prefetch_faults;

    NvU32 num_duplicate_faults;

    NvU32 num_replays;

    // Unique id (per-GPU) generated for tools events recording
    NvU32 batch_id;

    uvm_tracker_t tracker;

    // Boolean used to avoid sorting the fault batch by instance_ptr if we
    // determine at fetch time that all the faults in the batch report the same
    // instance_ptr
    bool is_single_instance_ptr;

    // Last fetched fault. Used for fault filtering.
    uvm_fault_buffer_entry_t *last_fault;
};

struct uvm_ats_fault_invalidate_struct
{
    // Whether the TLB batch contains any information
    bool            write_faults_in_batch;

    // Batch of TLB entries to be invalidated
    uvm_tlb_batch_t write_faults_tlb_batch;
};

typedef struct
{
    // Fault buffer information and structures provided by RM
    UvmGpuFaultInfo rm_info;

    // Maximum number of faults to be processed in batch before fetching new
    // entries from the GPU buffer
    NvU32 max_batch_size;

    struct uvm_replayable_fault_buffer_info_struct
    {
        // Maximum number of faults entries that can be stored in the buffer
        NvU32 max_faults;

        // Cached value of the GPU GET register to minimize the round-trips
        // over PCIe
        NvU32 cached_get;

        // Cached value of the GPU PUT register to minimize the round-trips over
        // PCIe
        NvU32 cached_put;

        // Policy that determines when GPU replays are issued during normal
        // fault servicing
        uvm_perf_fault_replay_policy_t replay_policy;

        // Tracker used to aggregate replay operations, needed for fault cancel
        // and GPU removal
        uvm_tracker_t replay_tracker;

        // If there is a ratio larger than replay_update_put_ratio of duplicate
        // faults in a batch, PUT pointer is updated before flushing the buffer
        // that comes before the replay method.
        NvU32 replay_update_put_ratio;

        // Fault statistics. These fields are per-GPU and most of them are only
        // updated during fault servicing, and can be safely incremented.
        // Migrations may be triggered by different GPUs and need to be
        // incremented using atomics
        struct
        {
            NvU64 num_prefetch_faults;

            NvU64 num_read_faults;

            NvU64 num_write_faults;

            NvU64 num_atomic_faults;

            NvU64 num_duplicate_faults;

            atomic64_t num_pages_out;

            atomic64_t num_pages_in;

            NvU64 num_replays;

            NvU64 num_replays_ack_all;
        } stats;

        // Number of uTLBs in the chip
        NvU32 utlb_count;

        // Context structure used to service a GPU fault batch
        uvm_fault_service_batch_context_t batch_service_context;

        // Structure used to coalesce fault servicing in a VA block
        uvm_service_block_context_t block_service_context;

        // Information required to invalidate stale ATS PTEs from the GPU TLBs
        uvm_ats_fault_invalidate_t ats_invalidate;
    } replayable;

    struct uvm_non_replayable_fault_buffer_info_struct
    {
        // Maximum number of faults entries that can be stored in the buffer
        NvU32 max_faults;

        // Tracker used to aggregate clear faulted operations, needed for GPU
        // removal
        uvm_tracker_t clear_faulted_tracker;

        // Buffer used to store elements popped out from the queue shared with
        // RM for fault servicing.
        void *shadow_buffer_copy;

        // Array of elements fetched from the GPU fault buffer. The number of
        // elements in this array is exactly max_batch_size
        uvm_fault_buffer_entry_t *fault_cache;

        // Fault statistics. See replayable fault stats for more details.
        struct
        {
            NvU64 num_read_faults;

            NvU64 num_write_faults;

            NvU64 num_atomic_faults;

            NvU64 num_physical_faults;

            atomic64_t num_pages_out;

            atomic64_t num_pages_in;
        } stats;

        // Tracker which temporarily holds the work pushed to service faults
        uvm_tracker_t fault_service_tracker;

        // Structure used to coalesce fault servicing in a VA block
        uvm_service_block_context_t block_service_context;

        // Unique id (per-GPU) generated for tools events recording
        NvU32 batch_id;

        // Information required to invalidate stale ATS PTEs from the GPU TLBs
        uvm_ats_fault_invalidate_t ats_invalidate;
    } non_replayable;

    // Flag that tells if prefetch faults are enabled in HW
    bool prefetch_faults_enabled;

    // Timestamp when prefetch faults where disabled last time
    NvU64 disable_prefetch_faults_timestamp;
} uvm_fault_buffer_info_t;

typedef struct
{
    // True if the platform supports HW coherence (P9) and RM has exposed the
    // GPU's memory as a NUMA node to the kernel.
    bool enabled;

    // Range in the system physical address space where the memory of this GPU
    // is mapped
    NvU64 system_memory_window_start;
    NvU64 system_memory_window_end;

    NvU64 memblock_size;

    unsigned node_id;
} uvm_numa_info_t;

struct uvm_access_counter_service_batch_context_struct
{
    uvm_access_counter_buffer_entry_t *notification_cache;

    NvU32 num_cached_notifications;

    struct
    {
        uvm_access_counter_buffer_entry_t   **notifications;

        NvU32                             num_notifications;

        // Boolean used to avoid sorting the fault batch by instance_ptr if we
        // determine at fetch time that all the access counter notifications in the
        // batch report the same instance_ptr
        bool is_single_instance_ptr;
    } virt;

    struct
    {
        uvm_access_counter_buffer_entry_t    **notifications;
        uvm_reverse_map_t                      *translations;

        NvU32                              num_notifications;

        // Boolean used to avoid sorting the fault batch by aperture if we
        // determine at fetch time that all the access counter notifications in the
        // batch report the same aperture
        bool                              is_single_aperture;
    } phys;

    // Helper page mask to compute the accessed pages within a VA block
    uvm_page_mask_t accessed_pages;

    // Structure used to coalesce access counter servicing in a VA block
    uvm_service_block_context_t block_service_context;

    // Unique id (per-GPU) generated for tools events recording
    NvU32 batch_id;
};

typedef struct
{
    // Values used to configure access counters in RM
    struct
    {
        UVM_ACCESS_COUNTER_GRANULARITY  granularity;
        UVM_ACCESS_COUNTER_USE_LIMIT    use_limit;
    } rm;

    // The following values are precomputed by the access counter notification
    // handling code. See comments for UVM_MAX_TRANSLATION_SIZE in
    // uvm_gpu_access_counters.c for more details.
    NvU64 translation_size;

    NvU64 translations_per_counter;

    NvU64 sub_granularity_region_size;

    NvU64 sub_granularity_regions_per_translation;
} uvm_gpu_access_counter_type_config_t;

typedef struct
{
    UvmGpuAccessCntrInfo rm_info;

    NvU32 max_notifications;

    NvU32 max_batch_size;

    // Cached value of the GPU GET register to minimize the round-trips
    // over PCIe
    NvU32 cached_get;

    // Cached value of the GPU PUT register to minimize the round-trips over
    // PCIe
    NvU32 cached_put;

    // Tracker used to aggregate access counters clear operations, needed for
    // GPU removal
    uvm_tracker_t clear_tracker;

    // Current access counter configuration. During normal operation this
    // information is computed once during GPU initialization. However, tests
    // may override it to try different configuration values.
    struct
    {
        uvm_gpu_access_counter_type_config_t mimc;
        uvm_gpu_access_counter_type_config_t momc;

        NvU32                                threshold;
    } current_config;

    // Access counter statistics
    struct
    {
        atomic64_t num_pages_out;

        atomic64_t num_pages_in;
    } stats;

    // Ignoring access counters means that notifications are left in the HW
    // buffer without being serviced.  Requests to ignore access counters
    // are counted since the suspend path inhibits access counter interrupts,
    // and the resume path needs to know whether to reenable them.
    NvU32 notifications_ignored_count;

    // Context structure used to service a GPU access counter batch
    uvm_access_counter_service_batch_context_t batch_service_context;

    // VA space that reconfigured the access counters configuration, if any.
    // Used in builtin tests only, to avoid reconfigurations from different
    // processes
    //
    // Locking: both readers and writers must hold the access counters ISR lock
    uvm_va_space_t *reconfiguration_owner;
} uvm_access_counter_buffer_info_t;

typedef struct
{
    // VA where the identity mapping should be mapped in the internal VA
    // space managed by uvm_gpu_t.address_space_tree (see below).
    NvU64 base;

    // Page tables with the mapping.
    uvm_page_table_range_vec_t *range_vec;
} uvm_gpu_identity_mapping_t;

// Root chunk mapping
typedef struct
{
    // Page table range representation of the mapping. Because a root chunk
    // fits into a single 2MB page, in practice the range consists of a single
    // 2MB PTE.
    uvm_page_table_range_t *range;

    // Number of mapped pages of size PAGE_SIZE.
    NvU32 num_mapped_pages;
} uvm_gpu_root_chunk_mapping_t;

typedef enum
{
    UVM_GPU_LINK_INVALID = 0,
    UVM_GPU_LINK_PCIE,
    UVM_GPU_LINK_NVLINK_1,
    UVM_GPU_LINK_NVLINK_2,
    UVM_GPU_LINK_NVLINK_3,




    UVM_GPU_LINK_MAX
} uvm_gpu_link_type_t;

// UVM does not support P2P copies on pre-Pascal GPUs. Pascal+ GPUs only
// support virtual addresses in P2P copies. Therefore, a peer identity mapping
// needs to be created.
// Ampere+ GPUs support physical peer copies, too, so identity mappings are not
// needed
typedef enum
{
    UVM_GPU_PEER_COPY_MODE_UNSUPPORTED,
    UVM_GPU_PEER_COPY_MODE_VIRTUAL,
    UVM_GPU_PEER_COPY_MODE_PHYSICAL,
    UVM_GPU_PEER_COPY_MODE_COUNT
} uvm_gpu_peer_copy_mode_t;

struct uvm_gpu_struct
{
    uvm_parent_gpu_t *parent;

    // Refcount of the gpu, i.e. how many times it has been retained. This is
    // roughly a count of how many times it has been registered with a VA space,
    // except that some paths retain the GPU temporarily without a VA space.
    //
    // While this is >0, the GPU can't be removed. This differs from gpu_kref,
    // which merely prevents the uvm_gpu_t object from being freed.
    //
    // In most cases this count is protected by the global lock: retaining a GPU
    // from a UUID and any release require the global lock to be taken. But it's
    // also useful for a caller to retain a GPU they've already retained, in
    // which case there's no need to take the global lock. This can happen when
    // an operation needs to drop the VA space lock but continue operating on a
    // GPU. This is an atomic variable to handle those cases.
    //
    // Security note: keep it as a 64-bit counter to prevent overflow cases (a
    // user can create a lot of va spaces and register the gpu with them).
    atomic64_t retained_count;

    // A unique uvm gpu id in range [1, UVM_ID_MAX_PROCESSORS); this is a copy
    // of the parent's id.
    uvm_gpu_id_t id;

    // A unique uvm global_gpu id in range [1, UVM_GLOBAL_ID_MAX_PROCESSORS)
    uvm_global_gpu_id_t global_id;

    // Should be UVM_GPU_MAGIC_VALUE. Used for memory checking.
    NvU64 magic;

    struct
    {
        // The amount of memory the GPU has in total, in bytes. If the GPU is in
        // ZeroFB testing mode, this will be 0.
        NvU64 size;

        // Max (inclusive) physical address of this GPU's memory that the driver
        // can allocate through PMM (PMA).
        NvU64 max_allocatable_address;
    } mem_info;

    struct
    {
        // Big page size used by the internal UVM VA space
        // Notably it may be different than the big page size used by a user's VA
        // space in general.
        NvU32 internal_size;
    } big_page;

    // Mapped registers needed to obtain the current GPU timestamp
    struct
    {
        volatile NvU32 *time0_register;
        volatile NvU32 *time1_register;
    } time;

    // Identity peer mappings are only defined when
    // peer_copy_mode == UVM_GPU_PEER_COPY_MODE_VIRTUAL
    uvm_gpu_identity_mapping_t peer_mappings[UVM_ID_MAX_GPUS];

    struct
    {
        // Mask of peer_gpus set
        //
        // We can use a regular processor id because P2P is not allowed between
        // partitioned GPUs when SMC is enabled
        uvm_processor_mask_t peer_gpu_mask;

        // lazily-populated array of peer GPUs, indexed by the peer's GPU index
        uvm_gpu_t *peer_gpus[UVM_ID_MAX_GPUS];

        // Leaf spinlock used to synchronize access to the peer_gpus table so that
        // it can be safely accessed from the access counters bottom half
        uvm_spinlock_t peer_gpus_lock;
    } peer_info;

    // Maximum number of subcontexts supported
    NvU32 max_subcontexts;

    // RM address space handle used in many of the UVM/RM APIs
    // Represents a GPU VA space within rm_device.
    //
    // In SR-IOV heavy, proxy channels are not associated with this address
    // space.
    uvmGpuAddressSpaceHandle rm_address_space;

    // Page tree used for the internal UVM VA space shared with RM
    uvm_page_tree_t address_space_tree;

    // Set to true during add_gpu() as soon as the RM's address space is moved
    // to the address_space_tree.
    bool rm_address_space_moved_to_page_tree;

    uvm_gpu_semaphore_pool_t *semaphore_pool;

    uvm_channel_manager_t *channel_manager;

    uvm_pmm_gpu_t pmm;

    // Flat linear mapping covering vidmem. This is a kernel mapping that is
    // only created in certain configurations.
    //
    // There are two mutually exclusive versions of the mapping. The simplest
    // version covers the entire GPU memory, and it is created during GPU
    // initialization. The dynamic version is a partial vidmem mapping that
    // creates and destroys mappings to GPU root chunks on demand.
    union
    {
        // Static mapping covering the whole GPU memory.
        uvm_gpu_identity_mapping_t static_flat_mapping;

        // Dynamic mapping of GPU memory.
        struct
        {
            // Array of root chunk mappings.
            uvm_gpu_root_chunk_mapping_t *array;

            // Number of elements in the array.
            size_t count;

            // Each bit in the bitlock protects a single root chunk mapping.
            uvm_bit_locks_t bitlocks;

        } root_chunk_mappings;
    };

    // Linear sysmem mappings. Mappings are added on demand, and removed upon
    // GPU deinitialization. The mappings are added to UVM's internal address
    // space i.e. they are kernel mappings.
    //
    // Only used in SR-IOV heavy.
    struct
    {
        // Size of each mapping, in bytes.
        NvU64 mapping_size;

        // Array of sysmem mappings.
        uvm_gpu_identity_mapping_t *array;

        // Number of elements in the array.
        size_t count;

        // Each bit in the bitlock protects a sysmem mapping.
        uvm_bit_locks_t bitlocks;
    } sysmem_mappings;

    // Reverse lookup table used to query the user mapping associated with a
    // sysmem (DMA) physical address.
    //
    // The system memory mapping information referred to by this field is
    // different from that of sysmem_mappings, because it relates to user
    // mappings (instead of kernel), and it is used in most configurations.
    uvm_pmm_sysmem_mappings_t pmm_reverse_sysmem_mappings;





    // ECC handling
    // In order to trap ECC errors as soon as possible the driver has the hw
    // interrupt register mapped directly. If an ECC interrupt is ever noticed
    // to be pending, then the UVM driver needs to:
    //
    //   1) ask RM to service interrupts, and then
    //   2) inspect the ECC error notifier state.
    //
    // Notably, checking for channel errors is not enough, because ECC errors
    // can be pending, even after a channel has become idle.
    //
    // See more details in uvm_gpu_check_ecc_error().
    struct
    {
        // Does the GPU have ECC enabled?
        bool enabled;

        // Direct mapping of the 32-bit part of the hw interrupt tree that has
        // the ECC bits.
        volatile NvU32 *hw_interrupt_tree_location;

        // Mask to get the ECC interrupt bits from the 32-bits above.
        NvU32 mask;

        // Set to true by RM when a fatal ECC error is encountered (requires
        // asking RM to service pending interrupts to be current).
        NvBool *error_notifier;
    } ecc;

    struct
    {
        NvU32 swizz_id;

        uvmGpuSessionHandle rm_session_handle;

        // RM device handle used in many of the UVM/RM APIs.
        //
        // Do not read this field directly, use uvm_gpu_device_handle instead.
        uvmGpuDeviceHandle rm_device;
    } smc;

    struct
    {
        struct proc_dir_entry *dir;

        struct proc_dir_entry *dir_symlink;

        struct proc_dir_entry *info_file;

        struct proc_dir_entry *dir_peers;
    } procfs;

    // Placeholder for per-GPU performance heuristics information
    uvm_perf_module_data_desc_t perf_modules_data[UVM_PERF_MODULE_TYPE_COUNT];
};

struct uvm_parent_gpu_struct
{
    // Reference count for how many places are holding on to a parent GPU
    // (internal to the UVM driver).  This includes any GPUs we know about, not
    // just GPUs that are registered with a VA space.  Most GPUs end up being
    // registered, but there are brief periods when they are not registered,
    // such as during interrupt handling, and in add_gpu() or remove_gpu().
    nv_kref_t gpu_kref;

    // The number of uvm_gpu_ts referencing this uvm_parent_gpu_t.
    NvU32 num_retained_gpus;

    uvm_gpu_t *gpus[UVM_ID_MAX_SUB_PROCESSORS];

    // Bitmap of valid child entries in the gpus[] table.  Used to retrieve a
    // usable child GPU in bottom-halves.
    DECLARE_BITMAP(valid_gpus, UVM_ID_MAX_SUB_PROCESSORS);

    // The gpu's uuid
    NvProcessorUuid uuid;

    // Nice printable name including the uvm gpu id, ascii name from RM and uuid
    char name[UVM_GPU_NICE_NAME_BUFFER_LENGTH];

    // GPU information and provided by RM (architecture, implementation,
    // hardware classes, etc.).
    UvmGpuInfo rm_info;

    // A unique uvm gpu id in range [1, UVM_ID_MAX_PROCESSORS)
    uvm_gpu_id_t id;

    // Reference to the Linux PCI device
    //
    // The reference to the PCI device remains valid as long as the GPU is
    // registered with RM's Linux layer (between nvUvmInterfaceRegisterGpu() and
    // nvUvmInterfaceUnregisterGpu()).
    struct pci_dev *pci_dev;

    // NVLINK Processing Unit (NPU) on PowerPC platforms. The NPU is a
    // collection of CPU-side PCI devices which bridge GPU NVLINKs and the CPU
    // memory bus.
    //
    // There is one PCI device per NVLINK. A set of NVLINKs connects to a single
    // GPU, and all NVLINKs for a given socket are collected logically under
    // this UVM NPU because some resources (such as register mappings) are
    // shared by all those NVLINKs. This means multiple GPUs may connect to the
    // same UVM NPU.
    uvm_ibm_npu_t *npu;

    // On kernels with NUMA support, this entry contains the closest CPU NUMA
    // node to this GPU. Otherwise, the value will be -1.
    int closest_cpu_numa_node;

    // RM device handle used in many of the UVM/RM APIs.
    //
    // Do not read this field directly, use uvm_gpu_device_handle instead.
    uvmGpuDeviceHandle rm_device;

    // The physical address range addressable by the GPU
    //
    // The GPU has its NV_PFB_XV_UPPER_ADDR register set by RM to
    // dma_addressable_start (in bifSetupDmaWindow_IMPL()) and hence when
    // referencing sysmem from the GPU, dma_addressable_start should be
    // subtracted from the physical address. The DMA mapping helpers like
    // uvm_gpu_map_cpu_pages() and uvm_gpu_dma_alloc_page() take care of that.
    NvU64 dma_addressable_start;
    NvU64 dma_addressable_limit;

    // Total size (in bytes) of physically mapped (with uvm_gpu_map_cpu_pages)
    // sysmem pages, used for leak detection.
    atomic64_t mapped_cpu_pages_size;

    // Hardware Abstraction Layer
    uvm_host_hal_t *host_hal;
    uvm_ce_hal_t *ce_hal;
    uvm_arch_hal_t *arch_hal;
    uvm_fault_buffer_hal_t *fault_buffer_hal;
    uvm_access_counter_buffer_hal_t *access_counter_buffer_hal;




    uvm_gpu_peer_copy_mode_t peer_copy_mode;

    // Virtualization mode of the GPU.
    UVM_VIRT_MODE virt_mode;

    // Whether the GPU can trigger faults on prefetch instructions
    bool prefetch_fault_supported;

    // Number of membars required to flush out HSHUB following a TLB invalidate
    NvU32 num_hshub_tlb_invalidate_membars;

    // Whether the channels can configure GPFIFO in vidmem
    bool gpfifo_in_vidmem_supported;

    bool replayable_faults_supported;

    bool non_replayable_faults_supported;

    bool access_counters_supported;

    bool fault_cancel_va_supported;

    // True if the GPU has hardware support for scoped atomics
    bool scoped_atomics_supported;

    // If true, a HW method can be used to clear a faulted channel.
    // If false, then the GPU supports clearing faulted channels using registers
    // instead of a HW method.
    // This value is only defined for GPUs that support non-replayable faults.
    bool has_clear_faulted_channel_method;

    // If true, a SW method can be used to clear a faulted channel.
    // If false, the HW method or the registers (whichever is available
    // according to has_clear_faulted_channel_method) needs to be used.
    //
    // This value is only defined for GPUs that support non-replayable faults.
    bool has_clear_faulted_channel_sw_method;

    bool sparse_mappings_supported;

    // Ampere(GA100) requires map->invalidate->remap->invalidate for page size
    // promotion
    bool map_remap_larger_page_promotion;

    bool plc_supported;

    // Parameters used by the TLB batching API
    struct
    {
        // Is the targeted (single page) VA invalidate supported at all?
        NvBool va_invalidate_supported;

        // Is the VA range invalidate supported?
        NvBool va_range_invalidate_supported;

        union
        {
            // Maximum (inclusive) number of single page invalidations before
            // falling back to invalidate all
            NvU32 max_pages;

            // Maximum (inclusive) number of range invalidations before falling
            // back to invalidate all
            NvU32 max_ranges;
        };
    } tlb_batch;

    // Largest VA (exclusive) which can be used for channel buffer mappings
    NvU64 max_channel_va;

    // Largest VA (exclusive) which Host can operate.
    NvU64 max_host_va;

    // Indicates whether the GPU can map sysmem with pages larger than 4k
    bool can_map_sysmem_with_large_pages;

    // VA base and size of the RM managed part of the internal UVM VA space.
    //
    // The internal UVM VA is shared with RM by RM controlling some of the top
    // level PDEs and leaving the rest for UVM to control.
    // On Pascal a single top level PDE covers 128 TB of VA and given that
    // semaphores and other allocations limited to 40bit are currently allocated
    // through RM, RM needs to control the [0, 128TB) VA range at least for now.
    // On Maxwell, limit RMs VA to [0, 128GB) that should easily fit
    // all RM allocations and leave enough space for UVM.
    NvU64 rm_va_base;
    NvU64 rm_va_size;

    // Base and size of the GPU VA used for uvm_mem_t allocations mapped in the
    // internal address_space_tree.
    NvU64 uvm_mem_va_base;
    NvU64 uvm_mem_va_size;

    // Base of the GPU VAs used for the vidmem and sysmem flat mappings.
    NvU64 flat_vidmem_va_base;
    NvU64 flat_sysmem_va_base;

    // Bitmap of allocation sizes for user memory supported by a GPU. PAGE_SIZE
    // is guaranteed to be both present and the smallest size.
    uvm_chunk_sizes_mask_t mmu_user_chunk_sizes;

    // Bitmap of allocation sizes that could be requested by the page tree for
    // a GPU
    uvm_chunk_sizes_mask_t mmu_kernel_chunk_sizes;

    struct
    {
        struct proc_dir_entry *dir;

        struct proc_dir_entry *fault_stats_file;

        struct proc_dir_entry *access_counters_file;
    } procfs;

    // Interrupt handling state and locks
    uvm_isr_info_t isr;

    // Fault buffer info. This is only valid if supports_replayable_faults is set to true
    uvm_fault_buffer_info_t fault_buffer_info;

    // NUMA info, mainly for ATS
    uvm_numa_info_t numa_info;

    // Access counter buffer info. This is only valid if supports_access_counters is set to true
    uvm_access_counter_buffer_info_t access_counter_buffer_info;

    // Number of uTLBs per GPC. This information is only valid on Pascal+ GPUs.
    NvU32 utlb_per_gpc_count;

    // In order to service GPU faults, UVM must be able to obtain the VA
    // space for each reported fault. The fault packet contains the
    // instance_ptr of the channel that was bound when the SMs triggered
    // the fault. On fault any instance pointer in the TSG may be
    // reported. This is a problem on Volta, which allow different channels
    // in the TSG to be bound to different VA spaces in order to support
    // subcontexts. In order to be able to obtain the correct VA space, HW
    // provides the subcontext id (or VEID) in addition to the instance_ptr.
    //
    // Summary:
    //
    // 1) Channels in a TSG may be in different VA spaces, identified by their
    // subcontext ID.
    // 2) Different subcontext IDs may map to the same or different VA spaces.
    // 3) On fault, any instance pointer in the TSG may be reported. The
    // reported subcontext ID identifies which VA space within the TSG actually
    // encountered the fault.
    //
    // Thus, UVM needs to keep track of all the instance pointers that belong
    // to the same TSG. We use two tables:
    //
    // - instance_ptr_table (instance_ptr -> subctx_info) this table maps
    // instance pointers to the subcontext info descriptor for the channel. If
    // the channel belongs to a subcontext, this descriptor will contain all
    // the VA spaces for the subcontexts in the same TSG. If the channel does
    // not belong to a subcontext, it will only contain a pointer to its VA
    // space.
    // - tsg_table (tsg_id -> subctx_info): this table also stores the
    // subctx information, but in this case it is indexed by TSG ID. Thus,
    // when a new channel bound to a subcontext is registered, it will check
    // first in this table if the subcontext information descriptor for its TSG
    // already exists, otherwise it will create it. Channels not bound to
    // subcontexts will not use this table.
    //
    // The bottom half reads the tables under
    // isr.replayable_faults_handler.lock, but a separate lock is necessary
    // because entries are added and removed from the table under the va_space
    // lock, and we can't take isr.replayable_faults_handler.lock while holding
    // the va_space lock.
    uvm_rb_tree_t tsg_table;

    uvm_rb_tree_t instance_ptr_table;
    uvm_spinlock_t instance_ptr_table_lock;

    // This is set to true if the GPU belongs to an SLI group. Else, set to false.
    bool sli_enabled;

    struct
    {
        bool supported;

        bool enabled;
    } smc;

    // Global statistics. These fields are per-GPU and most of them are only
    // updated during fault servicing, and can be safely incremented.
    struct
    {
        NvU64          num_replayable_faults;

        NvU64      num_non_replayable_faults;

        atomic64_t             num_pages_out;

        atomic64_t              num_pages_in;
    } stats;

    // Structure to hold nvswitch specific information. In an nvswitch
    // environment, rather than using the peer-id field of the PTE (which can
    // only address 8 gpus), all gpus are assigned a 47-bit physical address
    // space by the fabric manager. Any physical address access to these
    // physical address spaces are routed through the switch to the corresponding
    // peer.
    struct
    {
        bool is_nvswitch_connected;

        // 47-bit fabric memory physical offset that peer gpus need to access
        // to read a peer's memory
        NvU64 fabric_memory_window_start;
    } nvswitch_info;

    uvm_gpu_link_type_t sysmem_link;
    NvU32 sysmem_link_rate_mbyte_per_s;
};

static const char *uvm_gpu_name(uvm_gpu_t *gpu)
{
    return gpu->parent->name;
}

static const NvProcessorUuid *uvm_gpu_uuid(uvm_gpu_t *gpu)
{
    return &gpu->parent->uuid;
}

static uvmGpuDeviceHandle uvm_gpu_device_handle(uvm_gpu_t *gpu)
{
    if (gpu->parent->smc.enabled)
        return gpu->smc.rm_device;
    return gpu->parent->rm_device;
}

struct uvm_gpu_peer_struct
{
    // The fields in this global structure can only be inspected under one of
    // the following conditions:
    //
    // - The VA space lock is held for either read or write, both GPUs are
    //   registered in the VA space, and the corresponding bit in the
    //   va_space.enabled_peers bitmap is set.
    //
    // - The global lock is held.
    //
    // - While the global lock was held in the past, the two GPUs were detected
    //   to be NVLINK peers and were both retained.
    //
    // - While the global lock was held in the past, the two GPUs were detected
    //   to be PCIe peers and uvm_gpu_retain_pcie_peer_access() was called.
    //
    // - The peer_gpus_lock is held on one of the GPUs. In this case, the other
    //   GPU must be read from the original GPU's peer_gpus table. The fields
    //   will not change while the lock is held, but they may no longer be valid
    //   because the other GPU might be in teardown.

    // Peer Id associated with this device w.r.t. to a peer GPU.
    // Note: peerId (A -> B) != peerId (B -> A)
    // peer_id[0] from min(gpu_id_1, gpu_id_2) -> max(gpu_id_1, gpu_id_2)
    // peer_id[1] from max(gpu_id_1, gpu_id_2) -> min(gpu_id_1, gpu_id_2)
    NvU8 peer_ids[2];

    // Indirect peers are GPUs which can coherently access each others' memory
    // over NVLINK, but are routed through the CPU using the SYS aperture rather
    // than a PEER aperture
    NvU8 is_indirect_peer : 1;

    // The link type between the peer GPUs, currently either PCIe or NVLINK.
    // This field is used to determine the when this peer struct has been
    // initialized (link_type != UVM_GPU_LINK_INVALID). NVLink peers are
    // initialized at GPU registration time. PCIe peers are initialized when
    // the refcount below goes from 0 to 1.
    uvm_gpu_link_type_t link_type;

    // Maximum unidirectional bandwidth between the peers in megabytes per
    // second, not taking into account the protocols' overhead. The reported
    // bandwidth for indirect peers is zero. See UvmGpuP2PCapsParams.
    NvU32 total_link_line_rate_mbyte_per_s;

    // For PCIe, the number of times that this has been retained by a VA space.
    // For NVLINK this will always be 1.
    NvU64 ref_count;

    // This handle gets populated when enable_peer_access successfully creates
    // an NV50_P2P object. disable_peer_access resets the same on the object
    // deletion.
    NvHandle p2p_handle;

    struct {
        struct proc_dir_entry *peer_file[2];
        struct proc_dir_entry *peer_symlink_file[2];

        // GPU-A <-> GPU-B link is bidirectional, pairs[x][0] is always the
        // local GPU, while pairs[x][1] is the remote GPU. The table shall be
        // filled like so: [[GPU-A, GPU-B], [GPU-B, GPU-A]].
        uvm_gpu_t *pairs[2][2];
    } procfs;
};

// Initialize global gpu state
NV_STATUS uvm_gpu_init(void);

// Deinitialize global state (called from module exit)
void uvm_gpu_exit(void);

NV_STATUS uvm_gpu_init_va_space(uvm_va_space_t *va_space);

void uvm_gpu_exit_va_space(uvm_va_space_t *va_space);

static uvm_numa_info_t *uvm_gpu_numa_info(uvm_gpu_t *gpu)
{
    UVM_ASSERT(gpu->parent->numa_info.enabled);

    return &gpu->parent->numa_info;
}

static uvm_gpu_phys_address_t uvm_gpu_page_to_phys_address(uvm_gpu_t *gpu, struct page *page)
{
    uvm_numa_info_t *numa_info = uvm_gpu_numa_info(gpu);

    unsigned long sys_addr = page_to_pfn(page) << PAGE_SHIFT;
    unsigned long gpu_offset = sys_addr - numa_info->system_memory_window_start;

    UVM_ASSERT(page_to_nid(page) == numa_info->node_id);
    UVM_ASSERT(sys_addr >= numa_info->system_memory_window_start);
    UVM_ASSERT(sys_addr + PAGE_SIZE - 1 <= numa_info->system_memory_window_end);

    return uvm_gpu_phys_address(UVM_APERTURE_VID, gpu_offset);
}

// Note that there is a uvm_gpu_get() function defined in uvm_global.h to break
// a circular dep between global and gpu modules.

// Get a uvm_gpu_t by UUID.  This returns NULL if the GPU is not present.  This
// is the general purpose call that should be used normally.
// That is, unless a uvm_gpu_t for a specific SMC partition needs to be
// retrieved, in which case uvm_gpu_get_by_parent_and_swizz_id() must be used
// instead.
//
// LOCKING: requires the global lock to be held
uvm_gpu_t *uvm_gpu_get_by_uuid(const NvProcessorUuid *gpu_uuid);

// Get a uvm_parent_gpu_t by UUID.  Like uvm_gpu_get_by_uuid(), this function
// returns NULL if the GPU has not been registered.
//
// LOCKING: requires the global lock to be held
uvm_parent_gpu_t *uvm_parent_gpu_get_by_uuid(const NvProcessorUuid *gpu_uuid);

// Like uvm_parent_gpu_get_by_uuid(), but this variant does not assertion-check
// that the caller is holding the global_lock.  This is a narrower-purpose
// function, and is only intended for use by the top-half ISR, or other very
// limited cases.
uvm_parent_gpu_t *uvm_parent_gpu_get_by_uuid_locked(const NvProcessorUuid *gpu_uuid);

// Get the uvm_gpu_t for a partition by parent and swizzId. This returns NULL if
// the partition hasn't been registered. This call needs to be used instead of
// uvm_gpu_get_by_uuid() when a specific partition is targeted.
//
// LOCKING: requires the global lock to be held
uvm_gpu_t *uvm_gpu_get_by_parent_and_swizz_id(uvm_parent_gpu_t *parent_gpu, NvU32 swizz_id);

// Retain a gpu by uuid
// Returns the retained uvm_gpu_t in gpu_out on success
//
// LOCKING: Takes and releases the global lock for the caller.
NV_STATUS uvm_gpu_retain_by_uuid(const NvProcessorUuid *gpu_uuid,
                                 const uvm_rm_user_object_t *user_rm_device,
                                 uvm_gpu_t **gpu_out);

// Retain a gpu which is known to already be retained. Does NOT require the
// global lock to be held.
void uvm_gpu_retain(uvm_gpu_t *gpu);

// Release a gpu
// LOCKING: requires the global lock to be held
void uvm_gpu_release_locked(uvm_gpu_t *gpu);

// Like uvm_gpu_release_locked, but takes and releases the global lock for the
// caller.
void uvm_gpu_release(uvm_gpu_t *gpu);

static NvU64 uvm_gpu_retained_count(uvm_gpu_t *gpu)
{
    return atomic64_read(&gpu->retained_count);
}

// Decrease the refcount on the parent GPU object, and actually delete the object
// if the refcount hits zero.
void uvm_parent_gpu_kref_put(uvm_parent_gpu_t *gpu);

// Calculates peer table index using GPU ids.
NvU32 uvm_gpu_peer_table_index(uvm_gpu_id_t gpu_id1, uvm_gpu_id_t gpu_id2);

// Either retains an existing PCIe peer entry or creates a new one. In both
// cases the two GPUs are also each retained.
// LOCKING: requires the global lock to be held
NV_STATUS uvm_gpu_retain_pcie_peer_access(uvm_gpu_t *gpu0, uvm_gpu_t *gpu1);

// Releases a PCIe peer entry and the two GPUs.
// LOCKING: requires the global lock to be held
void uvm_gpu_release_pcie_peer_access(uvm_gpu_t *gpu0, uvm_gpu_t *gpu1);

// Get the aperture for local_gpu to use to map memory resident on remote_gpu.
// They must not be the same gpu.
uvm_aperture_t uvm_gpu_peer_aperture(uvm_gpu_t *local_gpu, uvm_gpu_t *remote_gpu);

// Get the processor id accessible by the given GPU for the given physical address
uvm_processor_id_t uvm_gpu_get_processor_id_by_address(uvm_gpu_t *gpu, uvm_gpu_phys_address_t addr);

// Get the P2P capabilities between the gpus with the given indexes
uvm_gpu_peer_t *uvm_gpu_index_peer_caps(uvm_gpu_id_t gpu_id1, uvm_gpu_id_t gpu_id2);

// Get the P2P capabilities between the given gpus
static uvm_gpu_peer_t *uvm_gpu_peer_caps(const uvm_gpu_t *gpu0, const uvm_gpu_t *gpu1)
{
    return uvm_gpu_index_peer_caps(gpu0->id, gpu1->id);
}

static bool uvm_gpus_are_nvswitch_connected(uvm_gpu_t *gpu1, uvm_gpu_t *gpu2)
{
    if (gpu1->parent->nvswitch_info.is_nvswitch_connected && gpu2->parent->nvswitch_info.is_nvswitch_connected) {
        UVM_ASSERT(uvm_gpu_peer_caps(gpu1, gpu2)->link_type >= UVM_GPU_LINK_NVLINK_2);
        return true;
    }

    return false;
}

static bool uvm_gpus_are_indirect_peers(uvm_gpu_t *gpu0, uvm_gpu_t *gpu1)
{
    uvm_gpu_peer_t *peer_caps = uvm_gpu_peer_caps(gpu0, gpu1);

    if (peer_caps->link_type != UVM_GPU_LINK_INVALID && peer_caps->is_indirect_peer) {
        UVM_ASSERT(gpu0->parent->numa_info.enabled);
        UVM_ASSERT(gpu1->parent->numa_info.enabled);
        UVM_ASSERT(peer_caps->link_type != UVM_GPU_LINK_PCIE);
        UVM_ASSERT(!uvm_gpus_are_nvswitch_connected(gpu0, gpu1));
        return true;
    }

    return false;
}

// Retrieve the virtual address corresponding to the given vidmem physical
// address, according to the linear vidmem mapping in the GPU kernel address
// space.
//
// The actual GPU mapping only exists if a full flat mapping, or a partial flat
// mapping covering the passed address, has been previously created.
static uvm_gpu_address_t uvm_gpu_address_virtual_from_vidmem_phys(uvm_gpu_t *gpu, NvU64 pa)
{
    UVM_ASSERT(uvm_mmu_gpu_needs_static_vidmem_mapping(gpu) || uvm_mmu_gpu_needs_dynamic_vidmem_mapping(gpu));
    UVM_ASSERT(pa <= gpu->mem_info.max_allocatable_address);

    return uvm_gpu_address_virtual(gpu->parent->flat_vidmem_va_base + pa);
}

// Retrieve the virtual address corresponding to the given sysmem physical
// address, according to the linear sysmem mapping in the GPU kernel address
// space.
//
// The actual GPU mapping only exists if a linear mapping covering the passed
// address has been previously created.
static uvm_gpu_address_t uvm_gpu_address_virtual_from_sysmem_phys(uvm_gpu_t *gpu, NvU64 pa)
{
    UVM_ASSERT(uvm_mmu_gpu_needs_dynamic_sysmem_mapping(gpu));
    UVM_ASSERT(pa <= (gpu->parent->dma_addressable_limit - gpu->parent->dma_addressable_start));

    return uvm_gpu_address_virtual(gpu->parent->flat_sysmem_va_base + pa);
}

static uvm_gpu_identity_mapping_t *uvm_gpu_get_peer_mapping(uvm_gpu_t *gpu, uvm_gpu_id_t peer_id)
{
    return &gpu->peer_mappings[uvm_id_gpu_index(peer_id)];
}

// Check for ECC errors
//
// Notably this check cannot be performed where it's not safe to call into RM.
NV_STATUS uvm_gpu_check_ecc_error(uvm_gpu_t *gpu);

// Check for ECC errors without calling into RM
//
// Calling into RM is problematic in many places, this check is always safe to do.
// Returns NV_WARN_MORE_PROCESSING_REQUIRED if there might be an ECC error and
// it's required to call uvm_gpu_check_ecc_error() to be sure.
NV_STATUS uvm_gpu_check_ecc_error_no_rm(uvm_gpu_t *gpu);

// Map size bytes of contiguous sysmem on the GPU for physical access
//
// size has to be aligned to PAGE_SIZE.
//
// Returns the physical address of the pages that can be used to access them on
// the GPU.
NV_STATUS uvm_gpu_map_cpu_pages(uvm_gpu_t *gpu, struct page *page, size_t size, NvU64 *dma_address_out);

// Unmap num_pages pages previously mapped with uvm_gpu_map_cpu_pages().
void uvm_gpu_unmap_cpu_pages(uvm_gpu_t *gpu, NvU64 dma_address, size_t size);

static NV_STATUS uvm_gpu_map_cpu_page(uvm_gpu_t *gpu, struct page *page, NvU64 *dma_address_out)
{
    return uvm_gpu_map_cpu_pages(gpu, page, PAGE_SIZE, dma_address_out);
}

static void uvm_gpu_unmap_cpu_page(uvm_gpu_t *gpu, NvU64 dma_address)
{
    uvm_gpu_unmap_cpu_pages(gpu, dma_address, PAGE_SIZE);
}

// Allocate and map a page of system DMA memory on the GPU for physical access
//
// Returns
// - the address of the page that can be used to access them on
//   the GPU in the dma_address_out parameter.
// - the address of allocated memory in CPU virtual address space.
void *uvm_gpu_dma_alloc_page(uvm_parent_gpu_t *parent_gpu,
                             gfp_t gfp_flags,
                             NvU64 *dma_address_out);

// Unmap and free size bytes of contiguous sysmem DMA previously allocated
// with uvm_gpu_map_cpu_pages().
void uvm_gpu_dma_free_page(uvm_parent_gpu_t *parent_gpu, void *va, NvU64 dma_address);

// Returns whether the given range is within the GPU's addressable VA ranges.
// It requires the input 'addr' to be in canonical form for platforms compliant
// to canonical form addresses, i.e., ARM64, and x86.
// Warning: This only checks whether the GPU's MMU can support the given
// address. Some HW units on that GPU might only support a smaller range.
//
// The GPU must be initialized before calling this function.
bool uvm_gpu_can_address(uvm_gpu_t *gpu, NvU64 addr, NvU64 size);

// Returns addr's canonical form for host systems that use canonical form
// addresses.
NvU64 uvm_parent_gpu_canonical_address(uvm_parent_gpu_t *parent_gpu, NvU64 addr);

static bool uvm_gpu_supports_eviction(uvm_gpu_t *gpu)
{






    // Eviction is supported only if the GPU supports replayable faults
    return gpu->parent->replayable_faults_supported;
}

static bool uvm_gpu_is_virt_mode_sriov_heavy(const uvm_gpu_t *gpu)
{
    return gpu->parent->virt_mode == UVM_VIRT_MODE_SRIOV_HEAVY;
}

static bool uvm_gpu_is_virt_mode_sriov_standard(const uvm_gpu_t *gpu)
{
    return gpu->parent->virt_mode == UVM_VIRT_MODE_SRIOV_STANDARD;
}

// Returns true if the virtualization mode is SR-IOV heavy or SR-IOV standard.
static bool uvm_gpu_is_virt_mode_sriov(const uvm_gpu_t *gpu)
{
    return uvm_gpu_is_virt_mode_sriov_heavy(gpu) || uvm_gpu_is_virt_mode_sriov_standard(gpu);
}

static bool uvm_gpu_uses_proxy_channel_pool(const uvm_gpu_t *gpu)
{
    return uvm_gpu_is_virt_mode_sriov_heavy(gpu);
}

uvm_aperture_t uvm_gpu_page_tree_init_location(const uvm_gpu_t *gpu);

// Debug print of GPU properties
void uvm_gpu_print(uvm_gpu_t *gpu);

// Add the given instance pointer -> user_channel mapping to this GPU. The bottom
// half GPU page fault handler uses this to look up the VA space for GPU faults.
NV_STATUS uvm_gpu_add_user_channel(uvm_gpu_t *gpu, uvm_user_channel_t *user_channel);
void uvm_gpu_remove_user_channel(uvm_gpu_t *gpu, uvm_user_channel_t *user_channel);

// Looks up an entry added by uvm_gpu_add_user_channel. Return codes:
//  NV_OK                        Translation successful
//  NV_ERR_INVALID_CHANNEL       Entry's instance pointer was not found
//  NV_ERR_PAGE_TABLE_NOT_AVAIL  Entry's instance pointer is valid but the entry
//                               targets an invalid subcontext
//
// out_va_space is valid if NV_OK is returned, otherwise it's NULL. The caller
// is responsibile for ensuring that the returned va_space can't be destroyed,
// so these functions should only be called from the bottom half.
NV_STATUS uvm_gpu_fault_entry_to_va_space(uvm_gpu_t *gpu,
                                          uvm_fault_buffer_entry_t *fault,
                                          uvm_va_space_t **out_va_space);

NV_STATUS uvm_gpu_access_counter_entry_to_va_space(uvm_gpu_t *gpu,
                                                   uvm_access_counter_buffer_entry_t *entry,
                                                   uvm_va_space_t **out_va_space);

typedef enum
{
    UVM_GPU_BUFFER_FLUSH_MODE_CACHED_PUT,
    UVM_GPU_BUFFER_FLUSH_MODE_UPDATE_PUT,
} uvm_gpu_buffer_flush_mode_t;

#endif // __UVM_GPU_H__