litmus-rt-ext-res.git - LITMUS^RT with extended reservations for Forbidden Zones paper @ RTAS'20

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// SPDX-License-Identifier: GPL-2.0
/*
 * Implementation of Gasket page table support.
 *
 * Copyright (C) 2018 Google, Inc.
 */

/*
 * Implementation of Gasket page table support.
 *
 * This file assumes 4kB pages throughout; can be factored out when necessary.
 *
 * Address format is as follows:
 * Simple addresses - those whose containing pages are directly placed in the
 * device's address translation registers - are laid out as:
 * [ 63 - 40: Unused | 39 - 28: 0 | 27 - 12: page index | 11 - 0: page offset ]
 * page index:  The index of the containing page in the device's address
 *              translation registers.
 * page offset: The index of the address into the containing page.
 *
 * Extended address - those whose containing pages are contained in a second-
 * level page table whose address is present in the device's address translation
 * registers - are laid out as:
 * [ 63 - 40: Unused | 39: flag | 38 - 37: 0 | 36 - 21: dev/level 0 index |
 *   20 - 12: host/level 1 index | 11 - 0: page offset ]
 * flag:        Marker indicating that this is an extended address. Always 1.
 * dev index:   The index of the first-level page in the device's extended
 *              address translation registers.
 * host index:  The index of the containing page in the [host-resident] second-
 *              level page table.
 * page offset: The index of the address into the containing [second-level]
 *              page.
 */
#include "gasket_page_table.h"

#include <linux/device.h>
#include <linux/file.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/pagemap.h>
#include <linux/vmalloc.h>

#include "gasket_constants.h"
#include "gasket_core.h"

/* Constants & utility macros */
/* The number of pages that can be mapped into each second-level page table. */
#define GASKET_PAGES_PER_SUBTABLE 512

/* The starting position of the page index in a simple virtual address. */
#define GASKET_SIMPLE_PAGE_SHIFT 12

/* Flag indicating that a [device] slot is valid for use. */
#define GASKET_VALID_SLOT_FLAG 1

/*
 * The starting position of the level 0 page index (i.e., the entry in the
 * device's extended address registers) in an extended address.
 * Also can be thought of as (log2(PAGE_SIZE) + log2(PAGES_PER_SUBTABLE)),
 * or (12 + 9).
 */
#define GASKET_EXTENDED_LVL0_SHIFT 21

/*
 * Number of first level pages that Gasket chips support. Equivalent to
 * log2(NUM_LVL0_PAGE_TABLES)
 *
 * At a maximum, allowing for a 34 bits address space (or 16GB)
 *   = GASKET_EXTENDED_LVL0_WIDTH + (log2(PAGE_SIZE) + log2(PAGES_PER_SUBTABLE)
 * or, = 13 + 9 + 12
 */
#define GASKET_EXTENDED_LVL0_WIDTH 13

/*
 * The starting position of the level 1 page index (i.e., the entry in the
 * host second-level/sub- table) in an extended address.
 */
#define GASKET_EXTENDED_LVL1_SHIFT 12

/* Type declarations */
/* Valid states for a struct gasket_page_table_entry. */
enum pte_status {
	PTE_FREE,
	PTE_INUSE,
};

/*
 * Mapping metadata for a single page.
 *
 * In this file, host-side page table entries are referred to as that (or PTEs).
 * Where device vs. host entries are differentiated, device-side or -visible
 * entries are called "slots". A slot may be either an entry in the device's
 * address translation table registers or an entry in a second-level page
 * table ("subtable").
 *
 * The full data in this structure is visible on the host [of course]. Only
 * the address contained in dma_addr is communicated to the device; that points
 * to the actual page mapped and described by this structure.
 */
struct gasket_page_table_entry {
	/* The status of this entry/slot: free or in use. */
	enum pte_status status;

	/* Address of the page in DMA space. */
	dma_addr_t dma_addr;

	/* Linux page descriptor for the page described by this structure. */
	struct page *page;

	/*
	 * Index for alignment into host vaddrs.
	 * When a user specifies a host address for a mapping, that address may
	 * not be page-aligned. Offset is the index into the containing page of
	 * the host address (i.e., host_vaddr & (PAGE_SIZE - 1)).
	 * This is necessary for translating between user-specified addresses
	 * and page-aligned addresses.
	 */
	int offset;

	/*
	 * If this is an extended and first-level entry, sublevel points
	 * to the second-level entries underneath this entry.
	 */
	struct gasket_page_table_entry *sublevel;
};

/*
 * Maintains virtual to physical address mapping for a coherent page that is
 * allocated by this module for a given device.
 * Note that coherent pages mappings virt mapping cannot be tracked by the
 * Linux kernel, and coherent pages don't have a struct page associated,
 * hence Linux kernel cannot perform a get_user_page_xx() on a phys address
 * that was allocated coherent.
 * This structure trivially implements this mechanism.
 */
struct gasket_coherent_page_entry {
	/* Phys address, dma'able by the owner device */
	dma_addr_t paddr;

	/* Kernel virtual address */
	u64 user_virt;

	/* User virtual address that was mapped by the mmap kernel subsystem */
	u64 kernel_virt;

	/*
	 * Whether this page has been mapped into a user land process virtual
	 * space
	 */
	u32 in_use;
};

/*
 * [Host-side] page table descriptor.
 *
 * This structure tracks the metadata necessary to manage both simple and
 * extended page tables.
 */
struct gasket_page_table {
	/* The config used to create this page table. */
	struct gasket_page_table_config config;

	/* The number of simple (single-level) entries in the page table. */
	uint num_simple_entries;

	/* The number of extended (two-level) entries in the page table. */
	uint num_extended_entries;

	/* Array of [host-side] page table entries. */
	struct gasket_page_table_entry *entries;

	/* Number of actively mapped kernel pages in this table. */
	uint num_active_pages;

	/* Device register: base of/first slot in the page table. */
	u64 __iomem *base_slot;

	/* Device register: holds the offset indicating the start of the
	 * extended address region of the device's address translation table.
	 */
	u64 __iomem *extended_offset_reg;

	/* Device structure for the underlying device. Only used for logging. */
	struct device *device;

	/* PCI system descriptor for the underlying device. */
	struct pci_dev *pci_dev;

	/* Location of the extended address bit for this Gasket device. */
	u64 extended_flag;

	/* Mutex to protect page table internals. */
	struct mutex mutex;

	/* Number of coherent pages accessible thru by this page table */
	int num_coherent_pages;

	/*
	 * List of coherent memory (physical) allocated for a device.
	 *
	 * This structure also remembers the user virtual mapping, this is
	 * hacky, but we need to do this because the kernel doesn't keep track
	 * of the user coherent pages (pfn pages), and virt to coherent page
	 * mapping.
	 * TODO: use find_vma() APIs to convert host address to vm_area, to
	 * dma_addr_t instead of storing user virtu address in
	 * gasket_coherent_page_entry
	 *
	 * Note that the user virtual mapping is created by the driver, in
	 * gasket_mmap function, so user_virt belongs in the driver anyhow.
	 */
	struct gasket_coherent_page_entry *coherent_pages;
};

/* Mapping declarations */
static int gasket_map_simple_pages(
	struct gasket_page_table *pg_tbl, ulong host_addr,
	ulong dev_addr, uint num_pages);
static int gasket_map_extended_pages(
	struct gasket_page_table *pg_tbl, ulong host_addr,
	ulong dev_addr, uint num_pages);
static int gasket_perform_mapping(
	struct gasket_page_table *pg_tbl,
	struct gasket_page_table_entry *pte_base, u64 __iomem *att_base,
	ulong host_addr, uint num_pages, int is_simple_mapping);

static int gasket_alloc_simple_entries(
	struct gasket_page_table *pg_tbl, ulong dev_addr, uint num_pages);
static int gasket_alloc_extended_entries(
	struct gasket_page_table *pg_tbl, ulong dev_addr, uint num_entries);
static int gasket_alloc_extended_subtable(
	struct gasket_page_table *pg_tbl, struct gasket_page_table_entry *pte,
	u64 __iomem *att_reg);

/* Unmapping declarations */
static void gasket_page_table_unmap_nolock(
	struct gasket_page_table *pg_tbl, ulong start_addr, uint num_pages);
static void gasket_page_table_unmap_all_nolock(
	struct gasket_page_table *pg_tbl);
static void gasket_unmap_simple_pages(
	struct gasket_page_table *pg_tbl, ulong start_addr, uint num_pages);
static void gasket_unmap_extended_pages(
	struct gasket_page_table *pg_tbl, ulong start_addr, uint num_pages);
static void gasket_perform_unmapping(
	struct gasket_page_table *pg_tbl,
	struct gasket_page_table_entry *pte_base, u64 __iomem *att_base,
	uint num_pages, int is_simple_mapping);

static void gasket_free_extended_subtable(
	struct gasket_page_table *pg_tbl, struct gasket_page_table_entry *pte,
	u64 __iomem *att_reg);
static bool gasket_release_page(struct page *page);

/* Other/utility declarations */
static inline bool gasket_addr_is_simple(
	struct gasket_page_table *pg_tbl, ulong addr);
static bool gasket_is_simple_dev_addr_bad(
	struct gasket_page_table *pg_tbl, ulong dev_addr, uint num_pages);
static bool gasket_is_extended_dev_addr_bad(
	struct gasket_page_table *pg_tbl, ulong dev_addr, uint num_pages);
static bool gasket_is_pte_range_free(
	struct gasket_page_table_entry *pte, uint num_entries);
static void gasket_page_table_garbage_collect_nolock(
	struct gasket_page_table *pg_tbl);

/* Address format declarations */
static ulong gasket_components_to_dev_address(
	struct gasket_page_table *pg_tbl, int is_simple, uint page_index,
	uint offset);
static int gasket_simple_page_idx(
	struct gasket_page_table *pg_tbl, ulong dev_addr);
static ulong gasket_extended_lvl0_page_idx(
	struct gasket_page_table *pg_tbl, ulong dev_addr);
static ulong gasket_extended_lvl1_page_idx(
	struct gasket_page_table *pg_tbl, ulong dev_addr);

static int is_coherent(struct gasket_page_table *pg_tbl, ulong host_addr);

/* Public/exported functions */
/* See gasket_page_table.h for description. */
int gasket_page_table_init(
	struct gasket_page_table **ppg_tbl,
	const struct gasket_bar_data *bar_data,
	const struct gasket_page_table_config *page_table_config,
	struct device *device, struct pci_dev *pci_dev)
{
	ulong bytes;
	struct gasket_page_table *pg_tbl;
	ulong total_entries = page_table_config->total_entries;

	/*
	 * TODO: Verify config->total_entries against value read from the
	 * hardware register that contains the page table size.
	 */
	if (total_entries == ULONG_MAX) {
		dev_dbg(device, "Error reading page table size. "
			"Initializing page table with size 0\n");
		total_entries = 0;
	}

	dev_dbg(device,
		"Attempting to initialize page table of size 0x%lx\n",
		total_entries);

	dev_dbg(device,
		"Table has base reg 0x%x, extended offset reg 0x%x\n",
		page_table_config->base_reg,
		page_table_config->extended_reg);

	*ppg_tbl = kzalloc(sizeof(**ppg_tbl), GFP_KERNEL);
	if (!*ppg_tbl) {
		dev_dbg(device, "No memory for page table\n");
		return -ENOMEM;
	}

	pg_tbl = *ppg_tbl;
	bytes = total_entries * sizeof(struct gasket_page_table_entry);
	if (bytes != 0) {
		pg_tbl->entries = vzalloc(bytes);
		if (!pg_tbl->entries) {
			dev_dbg(device,
				"No memory for address translation metadata\n");
			kfree(pg_tbl);
			*ppg_tbl = NULL;
			return -ENOMEM;
		}
	}

	mutex_init(&pg_tbl->mutex);
	memcpy(&pg_tbl->config, page_table_config, sizeof(*page_table_config));
	if (pg_tbl->config.mode == GASKET_PAGE_TABLE_MODE_NORMAL ||
	    pg_tbl->config.mode == GASKET_PAGE_TABLE_MODE_SIMPLE) {
		pg_tbl->num_simple_entries = total_entries;
		pg_tbl->num_extended_entries = 0;
		pg_tbl->extended_flag = 1ull << page_table_config->extended_bit;
	} else {
		pg_tbl->num_simple_entries = 0;
		pg_tbl->num_extended_entries = total_entries;
		pg_tbl->extended_flag = 0;
	}
	pg_tbl->num_active_pages = 0;
	pg_tbl->base_slot = (u64 __iomem *)&(
		bar_data->virt_base[page_table_config->base_reg]);
	pg_tbl->extended_offset_reg = (u64 __iomem *)&(
		bar_data->virt_base[page_table_config->extended_reg]);
	pg_tbl->device = get_device(device);
	pg_tbl->pci_dev = pci_dev_get(pci_dev);

	dev_dbg(device, "Page table initialized successfully\n");

	return 0;
}

/* See gasket_page_table.h for description. */
void gasket_page_table_cleanup(struct gasket_page_table *pg_tbl)
{
	/* Deallocate free second-level tables. */
	gasket_page_table_garbage_collect(pg_tbl);

	/* TODO: Check that all PTEs have been freed? */

	vfree(pg_tbl->entries);
	pg_tbl->entries = NULL;

	put_device(pg_tbl->device);
	pci_dev_put(pg_tbl->pci_dev);
	kfree(pg_tbl);
}

/* See gasket_page_table.h for description. */
int gasket_page_table_partition(
	struct gasket_page_table *pg_tbl, uint num_simple_entries)
{
	int i, start;

	mutex_lock(&pg_tbl->mutex);
	if (num_simple_entries > pg_tbl->config.total_entries) {
		mutex_unlock(&pg_tbl->mutex);
		return -EINVAL;
	}

	gasket_page_table_garbage_collect_nolock(pg_tbl);

	start = min(pg_tbl->num_simple_entries, num_simple_entries);

	for (i = start; i < pg_tbl->config.total_entries; i++) {
		if (pg_tbl->entries[i].status != PTE_FREE) {
			dev_err(pg_tbl->device, "entry %d is not free\n", i);
			mutex_unlock(&pg_tbl->mutex);
			return -EBUSY;
		}
	}

	pg_tbl->num_simple_entries = num_simple_entries;
	pg_tbl->num_extended_entries =
		pg_tbl->config.total_entries - num_simple_entries;
	writeq(num_simple_entries, pg_tbl->extended_offset_reg);

	mutex_unlock(&pg_tbl->mutex);
	return 0;
}
EXPORT_SYMBOL(gasket_page_table_partition);

/*
 * See gasket_page_table.h for general description.
 *
 * gasket_page_table_map calls either gasket_map_simple_pages() or
 * gasket_map_extended_pages() to actually perform the mapping.
 *


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