linux-nv-oot/drivers/video/tegra/nvmap/nvmap_fault.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * SPDX-FileCopyrightText: Copyright (c) 2011-2024 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
 */

#define pr_fmt(fmt)	"%s: " fmt, __func__

#include <trace/events/nvmap.h>
#include <linux/highmem.h>

#include "nvmap_priv.h"
#include "nvmap_alloc.h"

static void nvmap_vma_close(struct vm_area_struct *vma);

#define __atomic_add_unless atomic_fetch_add_unless
static vm_fault_t nvmap_vma_fault(struct vm_fault *vmf);

struct vm_operations_struct nvmap_vma_ops = {
	.open		= nvmap_vma_open,
	.close		= nvmap_vma_close,
	.fault		= nvmap_vma_fault,
};

int is_nvmap_vma(struct vm_area_struct *vma)
{
	return vma->vm_ops == &nvmap_vma_ops;
}

/* to ensure that the backing store for the VMA isn't freed while a fork'd
 * reference still exists, nvmap_vma_open increments the reference count on
 * the handle, and nvmap_vma_close decrements it. alternatively, we could
 * disallow copying of the vma, or behave like pmem and zap the pages. FIXME.
*/
void nvmap_vma_open(struct vm_area_struct *vma)
{
	struct nvmap_vma_priv *priv;
	struct nvmap_handle *h;
	struct nvmap_vma_list *vma_list, *tmp;
	struct list_head *tmp_head = NULL;
	pid_t current_pid = task_tgid_nr(current);
	bool vma_pos_found = false;
	size_t nr_page, i;
	int vma_open_count;

	priv = vma->vm_private_data;
	BUG_ON(!priv);
	BUG_ON(!priv->handle);

	h = priv->handle;
	nvmap_umaps_inc(h);

	mutex_lock(&h->lock);
	vma_open_count = atomic_inc_return(&priv->count);
	if (vma_open_count == 1 && h->heap_pgalloc) {
		nr_page = h->size >> PAGE_SHIFT;
		for (i = 0; i < nr_page; i++) {
			struct page *page = nvmap_to_page(h->pgalloc.pages[i]);
			/* This is necessry to avoid page being accounted
			 * under NR_FILE_MAPPED. This way NR_FILE_MAPPED would
			 * be fully accounted under NR_FILE_PAGES. This allows
			 * Android low mem killer detect low memory condition
			 * precisely.
			 * This has a side effect of inaccurate pss accounting
			 * for NvMap memory mapped into user space. Android
			 * procrank and NvMap Procrank both would have same
			 * issue. Subtracting NvMap_Procrank pss from
			 * procrank pss would give non-NvMap pss held by process
			 * and adding NvMap memory used by process represents
			 * entire memroy consumption by the process.
			 */
			atomic_inc(&page->_mapcount);
		}
	}
	mutex_unlock(&h->lock);

	vma_list = kmalloc(sizeof(*vma_list), GFP_KERNEL);
	if (vma_list) {
		mutex_lock(&h->lock);
		tmp_head = &h->vmas;

		/* insert vma into handle's vmas list in the increasing order of
		 * handle offsets
		 */
		list_for_each_entry(tmp, &h->vmas, list) {
			/* if vma exists in list, just increment refcount */
			if (tmp->vma == vma) {
				atomic_inc(&tmp->ref);
				kfree(vma_list);
				goto unlock;
			}

			if (!vma_pos_found && (current_pid == tmp->pid)) {
				if (vma->vm_pgoff < tmp->vma->vm_pgoff) {
					tmp_head = &tmp->list;
					vma_pos_found = true;
				} else {
					tmp_head = tmp->list.next;
				}
			}
		}

		vma_list->vma = vma;
		vma_list->pid = current_pid;
		vma_list->save_vm_flags = vma->vm_flags;
		atomic_set(&vma_list->ref, 1);
		list_add_tail(&vma_list->list, tmp_head);
unlock:
		mutex_unlock(&h->lock);
	} else {
		WARN(1, "vma not tracked");
	}
}

static void nvmap_vma_close(struct vm_area_struct *vma)
{
	struct nvmap_vma_priv *priv = vma->vm_private_data;
	struct nvmap_vma_list *vma_list, *tmp_list;
	struct nvmap_handle *h;
	bool vma_found = false;
	size_t nr_page, i;

	if (!priv)
		return;

	BUG_ON(!priv->handle);

	h = priv->handle;
	nr_page = h->size >> PAGE_SHIFT;

	mutex_lock(&h->lock);
	list_for_each_entry_safe(vma_list, tmp_list, &h->vmas, list) {
		if (vma_list->vma != vma)
			continue;
		if (atomic_dec_return(&vma_list->ref) == 0) {
			list_del(&vma_list->list);
			kfree(vma_list);
		}
		vma_found = true;
		break;
	}
	BUG_ON(!vma_found);
	nvmap_umaps_dec(h);

	if (__atomic_add_unless(&priv->count, -1, 0) == 1) {
		if (h->heap_pgalloc) {
			for (i = 0; i < nr_page; i++) {
				struct page *page;
				page = nvmap_to_page(h->pgalloc.pages[i]);
				atomic_dec(&page->_mapcount);
			}
		}
		mutex_unlock(&h->lock);
		if (priv->handle)
			nvmap_handle_put(priv->handle);
		vma->vm_private_data = NULL;
		kfree(priv);
	} else {
		mutex_unlock(&h->lock);
	}
}

static vm_fault_t nvmap_vma_fault(struct vm_fault *vmf)
#define vm_insert_pfn vmf_insert_pfn
{
	struct page *page;
	struct nvmap_vma_priv *priv;
	unsigned long offs;
	struct vm_area_struct *vma = vmf->vma;
	unsigned long vmf_address = vmf->address;

	offs = (unsigned long)(vmf_address - vma->vm_start);
	priv = vma->vm_private_data;
	if (!priv || !priv->handle || !priv->handle->alloc)
		return VM_FAULT_SIGBUS;

	offs += priv->offs;
	/* if the VMA was split for some reason, vm_pgoff will be the VMA's
	 * offset from the original VMA */
	offs += (vma->vm_pgoff << PAGE_SHIFT);

	if (offs >= priv->handle->size)
		return VM_FAULT_SIGBUS;

	if (!priv->handle->heap_pgalloc) {
		unsigned long pfn;

		BUG_ON(nvmap_get_heap_block_base(priv->handle->carveout) & ~PAGE_MASK);
		pfn = ((nvmap_get_heap_block_base(priv->handle->carveout) + offs) >> PAGE_SHIFT);
		if (!pfn_is_map_memory(pfn)) {
			vm_insert_pfn(vma,
				(unsigned long)vmf_address, pfn);
			return VM_FAULT_NOPAGE;
		}
		/* CMA memory would get here */
		page = pfn_to_page(pfn);
	} else {
		void *kaddr;

		offs >>= PAGE_SHIFT;
		if (atomic_read(&priv->handle->pgalloc.reserved))
			return VM_FAULT_SIGBUS;
		page = nvmap_to_page(priv->handle->pgalloc.pages[offs]);

		if (PageAnon(page)) {
			if (vma->vm_flags & VM_SHARED)
				return VM_FAULT_SIGSEGV;
		}

		if (!nvmap_handle_track_dirty(priv->handle))
			goto finish;
		mutex_lock(&priv->handle->lock);
		if (nvmap_page_dirty(priv->handle->pgalloc.pages[offs])) {
			mutex_unlock(&priv->handle->lock);
			goto finish;
		}

		/* inner cache maint */
		kaddr  = kmap(page);
		BUG_ON(!kaddr);
		inner_cache_maint(NVMAP_CACHE_OP_WB_INV, kaddr, PAGE_SIZE);
		kunmap(page);

		if (priv->handle->flags & NVMAP_HANDLE_INNER_CACHEABLE)
			goto make_dirty;

make_dirty:
		nvmap_page_mkdirty(&priv->handle->pgalloc.pages[offs]);
		atomic_inc(&priv->handle->pgalloc.ndirty);
		mutex_unlock(&priv->handle->lock);
	}

finish:
	if (page)
		get_page(page);

	vmf->page = page;
	return (page) ? 0 : VM_FAULT_SIGBUS;
}