drivers/vfio/pci/vfio_pci_rdwr.c

/*
 * VFIO PCI I/O Port & MMIO access
 *
 * Copyright (C) 2012 Red Hat, Inc.  All rights reserved.
 *     Author: Alex Williamson <alex.williamson@redhat.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Derived from original vfio:
 * Copyright 2010 Cisco Systems, Inc.  All rights reserved.
 * Author: Tom Lyon, pugs@cisco.com
 */

#include <linux/fs.h>
#include <linux/pci.h>
#include <linux/uaccess.h>
#include <linux/io.h>

#include "vfio_pci_private.h"

/* I/O Port BAR access */
ssize_t vfio_pci_io_readwrite(struct vfio_pci_device *vdev, char __user *buf,
			      size_t count, loff_t *ppos, bool iswrite)
{
	struct pci_dev *pdev = vdev->pdev;
	loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
	int bar = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
	void __iomem *io;
	size_t done = 0;

	if (!pci_resource_start(pdev, bar))
		return -EINVAL;

	if (pos + count > pci_resource_len(pdev, bar))
		return -EINVAL;

	if (!vdev->barmap[bar]) {
		int ret;

		ret = pci_request_selected_regions(pdev, 1 << bar, "vfio");
		if (ret)
			return ret;

		vdev->barmap[bar] = pci_iomap(pdev, bar, 0);

		if (!vdev->barmap[bar]) {
			pci_release_selected_regions(pdev, 1 << bar);
			return -EINVAL;
		}
	}

	io = vdev->barmap[bar];

	while (count) {
		int filled;

		if (count >= 3 && !(pos % 4)) {
			__le32 val;

			if (iswrite) {
				if (copy_from_user(&val, buf, 4))
					return -EFAULT;

				iowrite32(le32_to_cpu(val), io + pos);
			} else {
				val = cpu_to_le32(ioread32(io + pos));

				if (copy_to_user(buf, &val, 4))
					return -EFAULT;
			}

			filled = 4;

		} else if ((pos % 2) == 0 && count >= 2) {
			__le16 val;

			if (iswrite) {
				if (copy_from_user(&val, buf, 2))
					return -EFAULT;

				iowrite16(le16_to_cpu(val), io + pos);
			} else {
				val = cpu_to_le16(ioread16(io + pos));

				if (copy_to_user(buf, &val, 2))
					return -EFAULT;
			}

			filled = 2;
		} else {
			u8 val;

			if (iswrite) {
				if (copy_from_user(&val, buf, 1))
					return -EFAULT;

				iowrite8(val, io + pos);
			} else {
				val = ioread8(io + pos);

				if (copy_to_user(buf, &val, 1))
					return -EFAULT;
			}

			filled = 1;
		}

		count -= filled;
		done += filled;
		buf += filled;
		pos += filled;
	}

	*ppos += done;

	return done;
}

/*
 * MMIO BAR access
 * We handle two excluded ranges here as well, if the user tries to read
 * the ROM beyond what PCI tells us is available or the MSI-X table region,
 * we return 0xFF and writes are dropped.
 */
ssize_t vfio_pci_mem_readwrite(struct vfio_pci_device *vdev, char __user *buf,
			       size_t count, loff_t *ppos, bool iswrite)
{
	struct pci_dev *pdev = vdev->pdev;
	loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
	int bar = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
	void __iomem *io;
	resource_size_t end;
	size_t done = 0;
	size_t x_start = 0, x_end = 0; /* excluded range */

	if (!pci_resource_start(pdev, bar))
		return -EINVAL;

	end = pci_resource_len(pdev, bar);

	if (pos > end)
		return -EINVAL;

	if (pos == end)
		return 0;

	if (pos + count > end)
		count = end - pos;

	if (bar == PCI_ROM_RESOURCE) {
		io = pci_map_rom(pdev, &x_start);
		x_end = end;
	} else {
		if (!vdev->barmap[bar]) {
			int ret;

			ret = pci_request_selected_regions(pdev, 1 << bar,
							   "vfio");
			if (ret)
				return ret;

			vdev->barmap[bar] = pci_iomap(pdev, bar, 0);

			if (!vdev->barmap[bar]) {
				pci_release_selected_regions(pdev, 1 << bar);
				return -EINVAL;
			}
		}

		io = vdev->barmap[bar];

		if (bar == vdev->msix_bar) {
			x_start = vdev->msix_offset;
			x_end = vdev->msix_offset + vdev->msix_size;
		}
	}

	if (!io)
		return -EINVAL;

	while (count) {
		size_t fillable, filled;

		if (pos < x_start)
			fillable = x_start - pos;
		else if (pos >= x_end)
			fillable = end - pos;
		else
			fillable = 0;

		if (fillable >= 4 && !(pos % 4) && (count >= 4)) {
			__le32 val;

			if (iswrite) {
				if (copy_from_user(&val, buf, 4))
					goto out;

				iowrite32(le32_to_cpu(val), io + pos);
			} else {
				val = cpu_to_le32(ioread32(io + pos));

				if (copy_to_user(buf, &val, 4))
					goto out;
			}

			filled = 4;
		} else if (fillable >= 2 && !(pos % 2) && (count >= 2)) {
			__le16 val;

			if (iswrite) {
				if (copy_from_user(&val, buf, 2))
					goto out;

				iowrite16(le16_to_cpu(val), io + pos);
			} else {
				val = cpu_to_le16(ioread16(io + pos));

				if (copy_to_user(buf, &val, 2))
					goto out;
			}

			filled = 2;
		} else if (fillable) {
			u8 val;

			if (iswrite) {
				if (copy_from_user(&val, buf, 1))
					goto out;

				iowrite8(val, io + pos);
			} else {
				val = ioread8(io + pos);

				if (copy_to_user(buf, &val, 1))
					goto out;
			}

			filled = 1;
		} else {
			/* Drop writes, fill reads with FF */
			filled = min((size_t)(x_end - pos), count);
			if (!iswrite) {
				char val = 0xFF;
				size_t i;

				for (i = 0; i < filled; i++) {
					if (put_user(val, buf + i))
						goto out;
				}
			}

		}

		count -= filled;
		done += filled;
		buf += filled;
		pos += filled;
	}

	*ppos += done;

out:
	if (bar == PCI_ROM_RESOURCE)
		pci_unmap_rom(pdev, io);

	return count ? -EFAULT : done;
}