path: root/drivers/pci/p2pdma.c

// SPDX-License-Identifier: GPL-2.0
/*
 * PCI Peer 2 Peer DMA support.
 *
 * Copyright (c) 2016-2018, Logan Gunthorpe
 * Copyright (c) 2016-2017, Microsemi Corporation
 * Copyright (c) 2017, Christoph Hellwig
 * Copyright (c) 2018, Eideticom Inc.
 */

#define pr_fmt(fmt) "pci-p2pdma: " fmt
#include <linux/ctype.h>
#include <linux/pci-p2pdma.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/genalloc.h>
#include <linux/memremap.h>
#include <linux/percpu-refcount.h>
#include <linux/random.h>
#include <linux/seq_buf.h>
#include <linux/xarray.h>

enum pci_p2pdma_map_type {
	PCI_P2PDMA_MAP_UNKNOWN = 0,
	PCI_P2PDMA_MAP_NOT_SUPPORTED,
	PCI_P2PDMA_MAP_BUS_ADDR,
	PCI_P2PDMA_MAP_THRU_HOST_BRIDGE,
};

struct pci_p2pdma {
	struct gen_pool *pool;
	bool p2pmem_published;
	struct xarray map_types;
};

struct pci_p2pdma_pagemap {
	struct dev_pagemap pgmap;
	struct pci_dev *provider;
	u64 bus_offset;
};

static struct pci_p2pdma_pagemap *to_p2p_pgmap(struct dev_pagemap *pgmap)
{
	return container_of(pgmap, struct pci_p2pdma_pagemap, pgmap);
}

static ssize_t size_show(struct device *dev, struct device_attribute *attr,
			 char *buf)
{
	struct pci_dev *pdev = to_pci_dev(dev);
	size_t size = 0;

	if (pdev->p2pdma->pool)
		size = gen_pool_size(pdev->p2pdma->pool);

	return scnprintf(buf, PAGE_SIZE, "%zd\n", size);
}
static DEVICE_ATTR_RO(size);

static ssize_t available_show(struct device *dev, struct device_attribute *attr,
			      char *buf)
{
	struct pci_dev *pdev = to_pci_dev(dev);
	size_t avail = 0;

	if (pdev->p2pdma->pool)
		avail = gen_pool_avail(pdev->p2pdma->pool);

	return scnprintf(buf, PAGE_SIZE, "%zd\n", avail);
}
static DEVICE_ATTR_RO(available);

static ssize_t published_show(struct device *dev, struct device_attribute *attr,
			      char *buf)
{
	struct pci_dev *pdev = to_pci_dev(dev);

	return scnprintf(buf, PAGE_SIZE, "%d\n",
			 pdev->p2pdma->p2pmem_published);
}
static DEVICE_ATTR_RO(published);

static struct attribute *p2pmem_attrs[] = {
	&dev_attr_size.attr,
	&dev_attr_available.attr,
	&dev_attr_published.attr,
	NULL,
};

static const struct attribute_group p2pmem_group = {
	.attrs = p2pmem_attrs,
	.name = "p2pmem",
};

static void pci_p2pdma_release(void *data)
{
	struct pci_dev *pdev = data;
	struct pci_p2pdma *p2pdma = pdev->p2pdma;

	if (!p2pdma)
		return;

	/* Flush and disable pci_alloc_p2p_mem() */
	pdev->p2pdma = NULL;
	synchronize_rcu();

	gen_pool_destroy(p2pdma->pool);
	sysfs_remove_group(&pdev->dev.kobj, &p2pmem_group);
	xa_destroy(&p2pdma->map_types);
}

static int pci_p2pdma_setup(struct pci_dev *pdev)
{
	int error = -ENOMEM;
	struct pci_p2pdma *p2p;

	p2p = devm_kzalloc(&pdev->dev, sizeof(*p2p), GFP_KERNEL);
	if (!p2p)
		return -ENOMEM;

	xa_init(&p2p->map_types);

	p2p->pool = gen_pool_create(PAGE_SHIFT, dev_to_node(&pdev->dev));
	if (!p2p->pool)
		goto out;

	error = devm_add_action_or_reset(&pdev->dev, pci_p2pdma_release, pdev);
	if (error)
		goto out_pool_destroy;

	pdev->p2pdma = p2p;

	error = sysfs_create_group(&pdev->dev.kobj, &p2pmem_group);
	if (error)
		goto out_pool_destroy;

	return 0;

out_pool_destroy:
	pdev->p2pdma = NULL;
	gen_pool_destroy(p2p->pool);
out:
	devm_kfree(&pdev->dev, p2p);
	return error;
}

/**
 * pci_p2pdma_add_resource - add memory for use as p2p memory
 * @pdev: the device to add the memory to
 * @bar: PCI BAR to add
 * @size: size of the memory to add, may be zero to use the whole BAR
 * @offset: offset into the PCI BAR
 *
 * The memory will be given ZONE_DEVICE struct pages so that it may
 * be used with any DMA request.
 */
int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size,
			    u64 offset)
{
	struct pci_p2pdma_pagemap *p2p_pgmap;
	struct dev_pagemap *pgmap;
	void *addr;
	int error;

	if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM))
		return -EINVAL;

	if (offset >= pci_resource_len(pdev, bar))
		return -EINVAL;

	if (!size)
		size = pci_resource_len(pdev, bar) - offset;

	if (size + offset > pci_resource_len(pdev, bar))
		return -EINVAL;

	if (!pdev->p2pdma) {
		error = pci_p2pdma_setup(pdev);
		if (error)
			return error;
	}

	p2p_pgmap = devm_kzalloc(&pdev->dev, sizeof(*p2p_pgmap), GFP_KERNEL);
	if (!p2p_pgmap)
		return -ENOMEM;

	pgmap = &p2p_pgmap->pgmap;
	pgmap->range.start = pci_resource_start(pdev, bar) + offset;
	pgmap->range.end = pgmap->range.start + size - 1;
	pgmap->nr_range = 1;
	pgmap->type = MEMORY_DEVICE_PCI_P2PDMA;

	p2p_pgmap->provider = pdev;
	p2p_pgmap->bus_offset = pci_bus_address(pdev, bar) -
		pci_resource_start(pdev, bar);