open-gpu-kernel-modules/kernel-open/nvidia-uvm/uvm_populate_pageable.c

/*******************************************************************************
    Copyright (c) 2018-2021 NVIDIA Corporation

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#include "uvm_common.h"
#include "uvm_ioctl.h"
#include "uvm_linux.h"
#include "uvm_lock.h"
#include "uvm_api.h"
#include "uvm_va_range.h"
#include "uvm_va_space.h"
#include "uvm_populate_pageable.h"

static bool is_write_populate(struct vm_area_struct *vma, uvm_populate_permissions_t populate_permissions)
{
    switch (populate_permissions) {
        case UVM_POPULATE_PERMISSIONS_INHERIT:
            return vma->vm_flags & VM_WRITE;
        case UVM_POPULATE_PERMISSIONS_ANY:
            return false;
        case UVM_POPULATE_PERMISSIONS_WRITE:
            return true;
        default:
            UVM_ASSERT(0);
            return false;
    }
}

NV_STATUS uvm_populate_pageable_vma(struct vm_area_struct *vma,
                                    unsigned long start,
                                    unsigned long length,
                                    int min_prot,
                                    bool touch,
                                    uvm_populate_permissions_t populate_permissions)
{
    unsigned long vma_num_pages;
    unsigned long outer = start + length;
    const bool is_writable = is_write_populate(vma, populate_permissions);
    struct mm_struct *mm = vma->vm_mm;
    unsigned long vm_flags = vma->vm_flags;
    bool uvm_managed_vma;
    long ret;
    struct page **pages = NULL;
    NV_STATUS status = NV_OK;

    UVM_ASSERT(PAGE_ALIGNED(start));
    UVM_ASSERT(PAGE_ALIGNED(outer));
    UVM_ASSERT(vma->vm_end > start);
    UVM_ASSERT(vma->vm_start < outer);
    uvm_assert_mmap_lock_locked(mm);

    // On most CPU architectures, write permission implies RW permission.
    if (vm_flags & VM_WRITE)
        vm_flags = vm_flags | VM_READ;

    if ((vm_flags & min_prot) != min_prot)
        return NV_ERR_INVALID_ADDRESS;

    // Adjust to input range boundaries
    start = max(start, vma->vm_start);
    outer = min(outer, vma->vm_end);

    vma_num_pages = (outer - start) / PAGE_SIZE;

    // Please see the comment in uvm_ats_service_fault() regarding the usage of
    // the touch parameter for more details.
    if (touch) {
        pages = uvm_kvmalloc(vma_num_pages * sizeof(pages[0]));
        if (!pages)
            return NV_ERR_NO_MEMORY;
    }

    // If the input vma is managed by UVM, temporarily remove the record
    // associated with the locking of mmap_lock, in order to avoid a "locked
    // twice" validation error triggered when also acquiring mmap_lock in the
    // page fault handler. The page fault is caused by get_user_pages.
    uvm_managed_vma = uvm_file_is_nvidia_uvm(vma->vm_file);
    if (uvm_managed_vma)
        uvm_record_unlock_mmap_lock_read(mm);

    ret = NV_GET_USER_PAGES_REMOTE(NULL, mm, start, vma_num_pages, is_writable, 0, pages, NULL);

    if (uvm_managed_vma)
        uvm_record_lock_mmap_lock_read(mm);

    if (ret < 0) {
        status = errno_to_nv_status(ret);
        goto out;
    }

    // We couldn't populate all pages, return error
    if (ret < vma_num_pages) {
        if (touch) {
            unsigned long i;

            for (i = 0; i < ret; i++) {
                UVM_ASSERT(pages[i]);
                put_page(pages[i]);
            }
        }

        status = NV_ERR_NO_MEMORY;
        goto out;
    }

    if (touch) {
        unsigned long i;

        for (i = 0; i < vma_num_pages; i++) {
            uvm_touch_page(pages[i]);
            put_page(pages[i]);
        }
    }

out:
    uvm_kvfree(pages);
    return status;
}

NV_STATUS uvm_populate_pageable(struct mm_struct *mm,
                                const unsigned long start,
                                const unsigned long length,
                                int min_prot,
                                bool touch,
                                uvm_populate_permissions_t populate_permissions)
{
    struct vm_area_struct *vma;
    const unsigned long end = start + length;
    unsigned long prev_end = end;

    UVM_ASSERT(PAGE_ALIGNED(start));
    UVM_ASSERT(PAGE_ALIGNED(length));
    uvm_assert_mmap_lock_locked(mm);

    vma = find_vma_intersection(mm, start, end);
    if (!vma || (start < vma->vm_start))
         return NV_ERR_INVALID_ADDRESS;

    // VMAs are validated and populated one at a time, since they may have
    // different protection flags
    // Validation of VM_SPECIAL flags is delegated to get_user_pages
    for (; vma && vma->vm_start <= prev_end; vma = find_vma_intersection(mm, prev_end, end)) {
        NV_STATUS status = uvm_populate_pageable_vma(vma, start, end - start, min_prot, touch, populate_permissions);

        if (status != NV_OK)
            return status;

        if (vma->vm_end >= end)
            return NV_OK;

        prev_end = vma->vm_end;
    }

    // Input range not fully covered by VMAs
    return NV_ERR_INVALID_ADDRESS;
}

NV_STATUS uvm_api_populate_pageable(const UVM_POPULATE_PAGEABLE_PARAMS *params, struct file *filp)
{
    NV_STATUS status;
    bool allow_managed;
    bool skip_prot_check;
    int min_prot;
    uvm_va_space_t *va_space = uvm_va_space_get(filp);

    if (params->flags & ~UVM_POPULATE_PAGEABLE_FLAGS_ALL)
        return NV_ERR_INVALID_ARGUMENT;

    if ((params->flags & UVM_POPULATE_PAGEABLE_FLAGS_TEST_ALL) && !uvm_enable_builtin_tests) {
        UVM_INFO_PRINT("Test flag set for UVM_POPULATE_PAGEABLE. Did you mean to insmod with uvm_enable_builtin_tests=1?\n");
        return NV_ERR_INVALID_ARGUMENT;
    }

    // Population of managed ranges is only allowed for test purposes. The goal
    // is to validate that it is possible to populate pageable ranges backed by
    // VMAs with the VM_MIXEDMAP or VM_DONTEXPAND special flags set. But since
    // there is no portable way to force allocation of such memory from user
    // space, and it is not safe to change the flags of an already created
    // VMA from kernel space, we take advantage of the fact that managed ranges
    // have both special flags set at creation time (see uvm_mmap)
    allow_managed = params->flags & UVM_POPULATE_PAGEABLE_FLAG_ALLOW_MANAGED;

    skip_prot_check = params->flags & UVM_POPULATE_PAGEABLE_FLAG_SKIP_PROT_CHECK;
    if (skip_prot_check)
        min_prot = 0;
    else
        min_prot = VM_READ;

    // Check size, alignment and overflow. VMA validations are performed by
    // populate_pageable
    if (uvm_api_range_invalid(params->base, params->length))
        return NV_ERR_INVALID_ADDRESS;

    // mmap_lock is needed to traverse the vmas in the input range and call
    // into get_user_pages. Unlike most UVM APIs, this one is defined to only
    // work on current->mm, not the mm associated with the VA space (if any).
    uvm_down_read_mmap_lock(current->mm);

    if (allow_managed || uvm_va_space_range_empty(va_space, params->base, params->base + params->length - 1)) {
        status = uvm_populate_pageable(current->mm,
                                       params->base,
                                       params->length,
                                       min_prot,
                                       false,
                                       UVM_POPULATE_PERMISSIONS_INHERIT);
    }
    else {
        status = NV_ERR_INVALID_ADDRESS;
    }

    uvm_up_read_mmap_lock(current->mm);

    return status;
}