// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2023 MediaTek Inc.
 */

#include <linux/gzvm_drv.h>

/**
 * hva_to_pa_fast() - converts hva to pa in generic fast way
 * @hva: Host virtual address.
 *
 * Return: GZVM_PA_ERR_BAD for translation error
 */
u64 hva_to_pa_fast(u64 hva)
{
	struct page *page[1];
	u64 pfn;

	if (get_user_page_fast_only(hva, 0, page)) {
		pfn = page_to_phys(page[0]);
		put_page((struct page *)page);
		return pfn;
	}
	return GZVM_PA_ERR_BAD;
}

/**
 * hva_to_pa_slow() - converts hva to pa in a slow way
 * @hva: Host virtual address
 *
 * This function converts HVA to PA in a slow way because the target hva is not
 * yet allocated and mapped in the host stage1 page table, we cannot find it
 * directly from current page table.
 * Thus, we have to allocate it and this operation is much slower than directly
 * find via current page table.
 *
 * Context: This function may sleep
 * Return: PA or GZVM_PA_ERR_BAD for translation error
 */
u64 hva_to_pa_slow(u64 hva)
{
	struct page *page = NULL;
	u64 pfn = 0;
	int npages;

	npages = get_user_pages_unlocked(hva, 1, &page, 0);
	if (npages != 1)
		return GZVM_PA_ERR_BAD;

	if (page) {
		pfn = page_to_phys(page);
		put_page(page);
		return pfn;
	}

	return GZVM_PA_ERR_BAD;
}

static u64 __gzvm_gfn_to_pfn_memslot(struct gzvm_memslot *memslot, u64 gfn)
{
	u64 hva, pa;

	hva = gzvm_gfn_to_hva_memslot(memslot, gfn);

	pa = gzvm_hva_to_pa_arch(hva);
	if (pa != GZVM_PA_ERR_BAD)
		return PHYS_PFN(pa);

	pa = hva_to_pa_fast(hva);
	if (pa != GZVM_PA_ERR_BAD)
		return PHYS_PFN(pa);

	pa = hva_to_pa_slow(hva);
	if (pa != GZVM_PA_ERR_BAD)
		return PHYS_PFN(pa);

	return GZVM_PA_ERR_BAD;
}

/**
 * gzvm_gfn_to_pfn_memslot() - Translate gfn (guest ipa) to pfn (host pa),
 *			       result is in @pfn
 * @memslot: Pointer to struct gzvm_memslot.
 * @gfn: Guest frame number.
 * @pfn: Host page frame number.
 *
 * Return:
 * * 0			- Succeed
 * * -EFAULT		- Failed to convert
 */
int gzvm_gfn_to_pfn_memslot(struct gzvm_memslot *memslot, u64 gfn,
			    u64 *pfn)
{
	u64 __pfn;

	if (!memslot)
		return -EFAULT;

	__pfn = __gzvm_gfn_to_pfn_memslot(memslot, gfn);
	if (__pfn == GZVM_PA_ERR_BAD) {
		*pfn = 0;
		return -EFAULT;
	}

	*pfn = __pfn;

	return 0;
}

static int cmp_ppages(struct rb_node *node, const struct rb_node *parent)
{
	struct gzvm_pinned_page *a = container_of(node,
						  struct gzvm_pinned_page,
						  node);
	struct gzvm_pinned_page *b = container_of(parent,
						  struct gzvm_pinned_page,
						  node);

	if (a->ipa < b->ipa)
		return -1;
	if (a->ipa > b->ipa)
		return 1;
	return 0;
}

static int rb_ppage_cmp(const void *key, const struct rb_node *node)
{
	struct gzvm_pinned_page *p = container_of(node,
						  struct gzvm_pinned_page,
						  node);
	phys_addr_t ipa = (phys_addr_t)key;

	return (ipa < p->ipa) ? -1 : (ipa > p->ipa);
}

static int gzvm_insert_ppage(struct gzvm *vm, struct gzvm_pinned_page *ppage)
{
	if (rb_find_add(&ppage->node, &vm->pinned_pages, cmp_ppages))
		return -EEXIST;
	return 0;
}

static int pin_one_page(struct gzvm *vm, unsigned long hva, u64 gpa)
{
	unsigned int flags = FOLL_HWPOISON | FOLL_LONGTERM | FOLL_WRITE;
	struct gzvm_pinned_page *ppage = NULL;
	struct mm_struct *mm = current->mm;
	struct page *page = NULL;

	ppage = kmalloc(sizeof(*ppage), GFP_KERNEL_ACCOUNT);
	if (!ppage)
		return -ENOMEM;

	mmap_read_lock(mm);
	pin_user_pages(hva, 1, flags, &page, NULL);
	mmap_read_unlock(mm);

	if (!page) {
		kfree(ppage);
		return -EFAULT;
	}

	ppage->page = page;
	ppage->ipa = gpa;
	gzvm_insert_ppage(vm, ppage);

	return 0;
}

/**
 * gzvm_handle_relinquish() - Handle memory relinquish request from hypervisor
 *
 * @vcpu: Pointer to struct gzvm_vcpu_run in userspace
 * @ipa: Start address(gpa) of a reclaimed page
 *
 * Return: Always return 0 because there are no cases of failure
 */
int gzvm_handle_relinquish(struct gzvm_vcpu *vcpu, phys_addr_t ipa)
{
	struct gzvm_pinned_page *ppage;
	struct rb_node *node;
	struct gzvm *vm = vcpu->gzvm;

	node = rb_find((void *)ipa, &vm->pinned_pages, rb_ppage_cmp);

	if (node)
		rb_erase(node, &vm->pinned_pages);
	else
		return 0;

	ppage = container_of(node, struct gzvm_pinned_page, node);
	unpin_user_pages_dirty_lock(&ppage->page, 1, true);
	kfree(ppage);
	return 0;
}

static int handle_block_demand_page(struct gzvm *vm, int memslot_id, u64 gfn)
{
	unsigned long hva;
	u64 pfn, __gfn;
	int ret, i;

	u32 nr_entries = GZVM_BLOCK_BASED_DEMAND_PAGE_SIZE / PAGE_SIZE;
	struct gzvm_memslot *memslot = &vm->memslot[memslot_id];
	u64 start_gfn = ALIGN_DOWN(gfn, nr_entries);
	u32 total_pages = memslot->npages;
	u64 base_gfn = memslot->base_gfn;

	/* if the demand region is less than a block, adjust the nr_entries */
	if (start_gfn + nr_entries > base_gfn + total_pages)
		nr_entries = base_gfn + total_pages - start_gfn;

	mutex_lock(&vm->demand_paging_lock);
	for (i = 0, __gfn = start_gfn; i < nr_entries; i++, __gfn++) {
		ret = gzvm_gfn_to_pfn_memslot(&vm->memslot[memslot_id], __gfn,
					      &pfn);
		if (unlikely(ret)) {
			ret = -ERR_FAULT;
			goto err_unlock;
		}
		vm->demand_page_buffer[i] = pfn;

		hva = gzvm_gfn_to_hva_memslot(&vm->memslot[memslot_id], __gfn);
		ret = pin_one_page(vm, hva, PFN_PHYS(__gfn));
		if (ret)
			goto err_unlock;
	}

	ret = gzvm_arch_map_guest_block(vm->vm_id, memslot_id, start_gfn,
					nr_entries);
	if (unlikely(ret)) {
		ret = -EFAULT;
		goto err_unlock;
	}

err_unlock:
	mutex_unlock(&vm->demand_paging_lock);

	return ret;
}

static int handle_single_demand_page(struct gzvm *vm, int memslot_id, u64 gfn)
{
	unsigned long hva;
	int ret;
	u64 pfn;

	ret = gzvm_gfn_to_pfn_memslot(&vm->memslot[memslot_id], gfn, &pfn);
	if (unlikely(ret))
		return -EFAULT;

	ret = gzvm_arch_map_guest(vm->vm_id, memslot_id, pfn, gfn, 1);
	if (unlikely(ret))
		return -EFAULT;

	hva = gzvm_gfn_to_hva_memslot(&vm->memslot[memslot_id], gfn);
	return pin_one_page(vm, hva, PFN_PHYS(gfn));
}

/**
 * gzvm_handle_page_fault() - Handle guest page fault, find corresponding page
 *                            for the faulting gpa
 * @vcpu: Pointer to struct gzvm_vcpu_run of the faulting vcpu
 *
 * Return:
 * * 0		- Success to handle guest page fault
 * * -EFAULT	- Failed to map phys addr to guest's GPA
 */
int gzvm_handle_page_fault(struct gzvm_vcpu *vcpu)
{
	struct gzvm *vm = vcpu->gzvm;
	int memslot_id;
	u64 gfn;

	gfn = PHYS_PFN(vcpu->run->exception.fault_gpa);
	memslot_id = gzvm_find_memslot(vm, gfn);
	if (unlikely(memslot_id < 0))
		return -EFAULT;

	if (vm->demand_page_gran == PAGE_SIZE)
		return handle_single_demand_page(vm, memslot_id, gfn);
	else
		return handle_block_demand_page(vm, memslot_id, gfn);
}