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

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#ifndef __UVM_VA_SPACE_MM_H__
#define __UVM_VA_SPACE_MM_H__

#include "uvm_linux.h"
#include "uvm_forward_decl.h"
#include "uvm_lock.h"
#include "uvm_test_ioctl.h"
#include "nv-kref.h"

#include <linux/mmu_notifier.h>

struct uvm_va_space_mm_struct
{
    // The mm currently associated with this VA space. Most callers shouldn't
    // access this directly, but should instead use uvm_va_space_mm_retain()/
    // uvm_va_space_mm_release().
    //
    // The pointer itself is valid between uvm_va_space_mm_register() and
    // uvm_va_space_mm_unregister(), but should only be considered usable when
    // retained or current.
    struct mm_struct *mm;

#if UVM_CAN_USE_MMU_NOTIFIERS()
    struct mmu_notifier mmu_notifier;
#endif

    // Lock protecting the alive and retained_count fields.
    uvm_spinlock_t lock;

    // Whether the mm is usable. uvm_va_space_mm_register() marks the mm as
    // alive and uvm_va_space_mm_shutdown() marks it as dead.
    bool alive;

    // Refcount for uvm_va_space_mm_retain()/uvm_va_space_mm_release()
    NvU32 retained_count;

    // Wait queue for threads waiting for retainers to finish (retained_count
    // going to 0 when not alive).
    wait_queue_head_t last_retainer_wait_queue;

    // State which is only injected by test ioctls
    struct
    {
        // Whether uvm_va_space_mm_shutdown() should do a timed wait for other
        // threads to arrive.
        bool delay_shutdown;

        bool verbose;

        // Number of threads which have called uvm_va_space_mm_shutdown(). Only
        // used when delay_shutdown is true.
        atomic_t num_mm_shutdown_threads;
    } test;
};

// Whether the system can support creating an association between a VA space and
// an mm.
bool uvm_va_space_mm_enabled_system(void);

// Whether this VA space is associated with an mm. This must not be called
// before uvm_va_space_initialize().
bool uvm_va_space_mm_enabled(uvm_va_space_t *va_space);

// Registers current->mm with the va_space. A reference is taken on the mm,
// meaning that until uvm_va_space_mm_unregister() is called the mm will remain
// a valid object in memory (mm_count), but is not guaranteed to remain alive
// (mm_users).
//
// Use uvm_va_space_mm_retain() to retrieve the mm.
//
// Locking: mmap_lock and the VA space lock must both be held for write.
NV_STATUS uvm_va_space_mm_register(uvm_va_space_t *va_space);

// De-associate the mm from the va_space. This function won't return until all
// in-flight retainers have called uvm_va_space_mm_release(). Subsequent calls
// to uvm_va_space_mm_retain() will return NULL.
//
// This function may invoke uvm_va_space_mm_shutdown() so the caller must not
// hold either mmap_lock or the VA space lock. Since this API must provide the
// same guarantees as uvm_va_space_mm_shutdown(), the caller must also guarantee
// prior to calling this function that all GPUs in this VA space have stopped
// making accesses under this mm and will not be able to start again under that
// VA space.
//
// Locking: This function may take both mmap_lock and the VA space lock.
void uvm_va_space_mm_unregister(uvm_va_space_t *va_space);

// Retains the current mm registered with this VA space. If no mm is currently
// registered, or if the registered mm is in the process of tearing down, NULL
// is returned. Otherwise, the returned mm will remain valid for normal use
// (locking mmap_lock, find_vma, get_user_pages, cgroup-accounted allocations,
// etc) until uvm_va_space_mm_release() is called.
//
// Please, note that a retained mm could have mm->users == 0.
//
// It is NOT necessary to hold the VA space lock when calling this function.
struct mm_struct *uvm_va_space_mm_retain(uvm_va_space_t *va_space);

// Similar to uvm_va_space_mm_retain(), but falls back to returning current->mm
// when there is no mm registered with the VA space (that is,
// uvm_va_space_mm_enabled() would return false). This is both a convenience and
// an optimization of the common case in which current->mm == va_space_mm.
// uvm_va_space_mm_or_current_release() must be called to release the mm, and it
// must be called from the same thread which called
// uvm_va_space_mm_or_current_retain().
//
// If a non-NULL mm is returned, the guarantees described by
// uvm_va_space_mm_retain() apply. If uvm_va_space_mm_enabled() is false the
// caller is responsible for validating that the returned mm matches the desired
// mm before performing an operation such as vm_insert_page(). See
// uvm_va_range_vma_check().
//
// This should not be called from a kernel thread.
struct mm_struct *uvm_va_space_mm_or_current_retain(uvm_va_space_t *va_space);

// Convenience wrapper around uvm_va_space_mm_retain() which also locks
// mmap_lock for read if valid.
static struct mm_struct *uvm_va_space_mm_retain_lock(uvm_va_space_t *va_space)
{
    struct mm_struct *mm = uvm_va_space_mm_retain(va_space);
    if (mm)
        uvm_down_read_mmap_lock(mm);
    return mm;
}

// Convenience wrapper around uvm_va_space_mm_or_current_retain() which also
// locks mmap_lock for read if valid.
static struct mm_struct *uvm_va_space_mm_or_current_retain_lock(uvm_va_space_t *va_space)
{
    struct mm_struct *mm = uvm_va_space_mm_or_current_retain(va_space);
    if (mm)
        uvm_down_read_mmap_lock(mm);
    return mm;
}

// Counterpart to uvm_va_space_mm_retain(). After this call, the mm must not be
// used again without another call to uvm_va_space_mm_retain().
void uvm_va_space_mm_release(uvm_va_space_t *va_space);

// Counterpart to uvm_va_space_mm_or_current_retain(). Must be called from the
// same thread which called uvm_va_space_mm_or_current_retain(). mm may be NULL,
// in which case this is a no-op.
void uvm_va_space_mm_or_current_release(uvm_va_space_t *va_space, struct mm_struct *mm);

static void uvm_va_space_mm_release_unlock(uvm_va_space_t *va_space, struct mm_struct *mm)
{
    if (mm) {
        uvm_up_read_mmap_lock(mm);
        uvm_va_space_mm_release(va_space);
    }
}

static void uvm_va_space_mm_or_current_release_unlock(uvm_va_space_t *va_space, struct mm_struct *mm)
{
    if (mm)
        uvm_up_read_mmap_lock(mm);
    uvm_va_space_mm_or_current_release(va_space, mm);
}

NV_STATUS uvm_test_va_space_mm_retain(UVM_TEST_VA_SPACE_MM_RETAIN_PARAMS *params, struct file *filp);
NV_STATUS uvm_test_va_space_mm_delay_shutdown(UVM_TEST_VA_SPACE_MM_DELAY_SHUTDOWN_PARAMS *params, struct file *filp);

#endif // __UVM_VA_SPACE_MM_H__