vfio_pci.c

/*
 * 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/device.h>
#include <linux/eventfd.h>
#include <linux/file.h>
#include <linux/interrupt.h>
#include <linux/iommu.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/notifier.h>
#include <linux/pci.h>
#include <linux/pm_runtime.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/uaccess.h>
#include <linux/vfio.h>
#include <linux/vgaarb.h>

#include "vfio_pci_private.h"

#define DRIVER_VERSION  "0.2"
#define DRIVER_AUTHOR   "Alex Williamson <alex.williamson@redhat.com>"
#define DRIVER_DESC     "VFIO PCI - User Level meta-driver"

static bool nointxmask;
module_param_named(nointxmask, nointxmask, bool, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(nointxmask,
		  "Disable support for PCI 2.3 style INTx masking.  If this resolves problems for specific devices, report lspci -vvvxxx to linux-pci@vger.kernel.org so the device can be fixed automatically via the broken_intx_masking flag.");

#ifdef CONFIG_VFIO_PCI_VGA
static bool disable_vga;
module_param(disable_vga, bool, S_IRUGO);
MODULE_PARM_DESC(disable_vga, "Disable VGA resource access through vfio-pci");
#endif

static DEFINE_MUTEX(driver_lock);

static inline bool vfio_vga_disabled(void)
{
#ifdef CONFIG_VFIO_PCI_VGA
	return disable_vga;
#else
	return true;
#endif
}

/*
 * Our VGA arbiter participation is limited since we don't know anything
 * about the device itself.  However, if the device is the only VGA device
 * downstream of a bridge and VFIO VGA support is disabled, then we can
 * safely return legacy VGA IO and memory as not decoded since the user
 * has no way to get to it and routing can be disabled externally at the
 * bridge.
 */
static unsigned int vfio_pci_set_vga_decode(void *opaque, bool single_vga)
{
	struct vfio_pci_device *vdev = opaque;
	struct pci_dev *tmp = NULL, *pdev = vdev->pdev;
	unsigned char max_busnr;
	unsigned int decodes;

	if (single_vga || !vfio_vga_disabled() || pci_is_root_bus(pdev->bus))
		return VGA_RSRC_NORMAL_IO | VGA_RSRC_NORMAL_MEM |
		       VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM;

	max_busnr = pci_bus_max_busnr(pdev->bus);
	decodes = VGA_RSRC_NORMAL_IO | VGA_RSRC_NORMAL_MEM;

	while ((tmp = pci_get_class(PCI_CLASS_DISPLAY_VGA << 8, tmp)) != NULL) {
		if (tmp == pdev ||
		    pci_domain_nr(tmp->bus) != pci_domain_nr(pdev->bus) ||
		    pci_is_root_bus(tmp->bus))
			continue;

		if (tmp->bus->number >= pdev->bus->number &&
		    tmp->bus->number <= max_busnr) {
			pci_dev_put(tmp);
			decodes |= VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM;
			break;
		}
	}

	return decodes;
}

static inline bool vfio_pci_is_vga(struct pci_dev *pdev)
{
	return (pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA;
}

static void vfio_pci_try_bus_reset(struct vfio_pci_device *vdev);

static int vfio_pci_enable(struct vfio_pci_device *vdev)
{
	struct pci_dev *pdev = vdev->pdev;
	int ret;
	u16 cmd;
	u8 msix_pos;

	/* Don't allow our initial saved state to include busmaster */
	pci_clear_master(pdev);

	ret = pci_enable_device(pdev);
	if (ret)
		return ret;

	vdev->reset_works = (pci_reset_function(pdev) == 0);
	pci_save_state(pdev);
	vdev->pci_saved_state = pci_store_saved_state(pdev);
	if (!vdev->pci_saved_state)
		pr_debug("%s: Couldn't store %s saved state\n",
			 __func__, dev_name(&pdev->dev));

	ret = vfio_config_init(vdev);
	if (ret) {
		kfree(vdev->pci_saved_state);
		vdev->pci_saved_state = NULL;
		pci_disable_device(pdev);
		return ret;
	}

	if (likely(!nointxmask))
		vdev->pci_2_3 = pci_intx_mask_supported(pdev);

	pci_read_config_word(pdev, PCI_COMMAND, &cmd);
	if (vdev->pci_2_3 && (cmd & PCI_COMMAND_INTX_DISABLE)) {
		cmd &= ~PCI_COMMAND_INTX_DISABLE;
		pci_write_config_word(pdev, PCI_COMMAND, cmd);
	}

	msix_pos = pdev->msix_cap;
	if (msix_pos) {
		u16 flags;
		u32 table;

		pci_read_config_word(pdev, msix_pos + PCI_MSIX_FLAGS, &flags);
		pci_read_config_dword(pdev, msix_pos + PCI_MSIX_TABLE, &table);

		vdev->msix_bar = table & PCI_MSIX_TABLE_BIR;
		vdev->msix_offset = table & PCI_MSIX_TABLE_OFFSET;
		vdev->msix_size = ((flags & PCI_MSIX_FLAGS_QSIZE) + 1) * 16;
	} else
		vdev->msix_bar = 0xFF;

	if (!vfio_vga_disabled() && vfio_pci_is_vga(pdev))
		vdev->has_vga = true;

	return 0;
}

static void vfio_pci_disable(struct vfio_pci_device *vdev)
{
	struct pci_dev *pdev = vdev->pdev;
	int bar;

	/* Stop the device from further DMA */
	pci_clear_master(pdev);

	vfio_pci_set_irqs_ioctl(vdev, VFIO_IRQ_SET_DATA_NONE |
				VFIO_IRQ_SET_ACTION_TRIGGER,
				vdev->irq_type, 0, 0, NULL);

	vdev->virq_disabled = false;

	vfio_config_free(vdev);

	for (bar = PCI_STD_RESOURCES; bar <= PCI_STD_RESOURCE_END; bar++) {
		if (!vdev->barmap[bar])
			continue;
		pci_iounmap(pdev, vdev->barmap[bar]);
		pci_release_selected_regions(pdev, 1 << bar);
		vdev->barmap[bar] = NULL;
	}

	vdev->needs_reset = true;

	/*
	 * If we have saved state, restore it.  If we can reset the device,
	 * even better.  Resetting with current state seems better than
	 * nothing, but saving and restoring current state without reset
	 * is just busy work.
	 */
	if (pci_load_and_free_saved_state(pdev, &vdev->pci_saved_state)) {
		pr_info("%s: Couldn't reload %s saved state\n",
			__func__, dev_name(&pdev->dev));

		if (!vdev->reset_works)
			goto out;

		pci_save_state(pdev);
	}

	/*
	 * Disable INTx and MSI, presumably to avoid spurious interrupts
	 * during reset.  Stolen from pci_reset_function()
	 */
	pci_write_config_word(pdev, PCI_COMMAND, PCI_COMMAND_INTX_DISABLE);

	/*
	 * Try to reset the device.  The success of this is dependent on
	 * being able to lock the device, which is not always possible.
	 */
	if (vdev->reset_works) {
		int ret = pci_try_reset_function(pdev);
		if (ret)
			pr_warn("%s: Failed to reset device %s (%d)\n",
				__func__, dev_name(&pdev->dev), ret);
		else
			vdev->needs_reset = false;
	}

	pci_restore_state(pdev);
out:
	pci_disable_device(pdev);

	vfio_pci_try_bus_reset(vdev);
}

static void vfio_pci_release(void *device_data)
{
	struct vfio_pci_device *vdev = device_data;

	mutex_lock(&driver_lock);

	if (!(--vdev->refcnt)) {
		vfio_spapr_pci_eeh_release(vdev->pdev);
		vfio_pci_disable(vdev);
	}

	mutex_unlock(&driver_lock);

	module_put(THIS_MODULE);
}

static int vfio_pci_open(void *device_data)
{
	struct vfio_pci_device *vdev = device_data;
	int ret = 0;

	if (!try_module_get(THIS_MODULE))
		return -ENODEV;

	mutex_lock(&driver_lock);

	if (!vdev->refcnt) {
		ret = vfio_pci_enable(vdev);
		if (ret)
			goto error;

		vfio_spapr_pci_eeh_open(vdev->pdev);
	}
	vdev->refcnt++;
error:
	mutex_unlock(&driver_lock);
	if (ret)
		module_put(THIS_MODULE);
	return ret;
}

static int vfio_pci_get_irq_count(struct vfio_pci_device *vdev, int irq_type)
{
	if (irq_type == VFIO_PCI_INTX_IRQ_INDEX) {
		u8 pin;
		pci_read_config_byte(vdev->pdev, PCI_INTERRUPT_PIN, &pin);
		if (IS_ENABLED(CONFIG_VFIO_PCI_INTX) && pin)
			return 1;

	} else if (irq_type == VFIO_PCI_MSI_IRQ_INDEX) {
		u8 pos;
		u16 flags;

		pos = vdev->pdev->msi_cap;
		if (pos) {
			pci_read_config_word(vdev->pdev,
					     pos + PCI_MSI_FLAGS, &flags);
			return 1 << ((flags & PCI_MSI_FLAGS_QMASK) >> 1);
		}
	} else if (irq_type == VFIO_PCI_MSIX_IRQ_INDEX) {
		u8 pos;
		u16 flags;

		pos = vdev->pdev->msix_cap;
		if (pos) {
			pci_read_config_word(vdev->pdev,
					     pos + PCI_MSIX_FLAGS, &flags);

			return (flags & PCI_MSIX_FLAGS_QSIZE) + 1;
		}
	} else if (irq_type == VFIO_PCI_ERR_IRQ_INDEX) {
		if (pci_is_pcie(vdev->pdev))
			return 1;
	} else if (irq_type == VFIO_PCI_REQ_IRQ_INDEX) {
		return 1;
	}

	return 0;
}

static int vfio_pci_count_devs(struct pci_dev *pdev, void *data)
{
	(*(int *)data)++;
	return 0;
}

struct vfio_pci_fill_info {
	int max;
	int cur;
	struct vfio_pci_dependent_device *devices;
};

static int vfio_pci_fill_devs(struct pci_dev *pdev, void *data)
{
	struct vfio_pci_fill_info *fill = data;
	struct iommu_group *iommu_group;

	if (fill->cur == fill->max)
		return -EAGAIN; /* Something changed, try again */

	iommu_group = iommu_group_get(&pdev->dev);
	if (!iommu_group)
		return -EPERM; /* Cannot reset non-isolated devices */

	fill->devices[fill->cur].group_id = iommu_group_id(iommu_group);
	fill->devices[fill->cur].segment = pci_domain_nr(pdev->bus);
	fill->devices[fill->cur].bus = pdev->bus->number;
	fill->devices[fill->cur].devfn = pdev->devfn;
	fill->cur++;
	iommu_group_put(iommu_group);
	return 0;
}

struct vfio_pci_group_entry {
	struct vfio_group *group;
	int id;
};

struct vfio_pci_group_info {
	int count;
	struct vfio_pci_group_entry *groups;
};

static int vfio_pci_validate_devs(struct pci_dev *pdev, void *data)
{
	struct vfio_pci_group_info *info = data;
	struct iommu_group *group;
	int id, i;

	group = iommu_group_get(&pdev->dev);
	if (!group)
		return -EPERM;

	id = iommu_group_id(group);

	for (i = 0; i < info->count; i++)
		if (info->groups[i].id == id)
			break;

	iommu_group_put(group);

	return (i == info->count) ? -EINVAL : 0;
}

static bool vfio_pci_dev_below_slot(struct pci_dev *pdev, struct pci_slot *slot)
{
	for (; pdev; pdev = pdev->bus->self)
		if (pdev->bus == slot->bus)
			return (pdev->slot == slot);
	return false;
}

struct vfio_pci_walk_info {
	int (*fn)(struct pci_dev *, void *data);
	void *data;
	struct pci_dev *pdev;
	bool slot;
	int ret;
};

static int vfio_pci_walk_wrapper(struct pci_dev *pdev, void *data)
{
	struct vfio_pci_walk_info *walk = data;

	if (!walk->slot || vfio_pci_dev_below_slot(pdev, walk->pdev->slot))
		walk->ret = walk->fn(pdev, walk->data);

	return walk->ret;
}

static int vfio_pci_for_each_slot_or_bus(struct pci_dev *pdev,
					 int (*fn)(struct pci_dev *,
						   void *data), void *data,
					 bool slot)
{
	struct vfio_pci_walk_info walk = {
		.fn = fn, .data = data, .pdev = pdev, .slot = slot, .ret = 0,
	};

	pci_walk_bus(pdev->bus, vfio_pci_walk_wrapper, &walk);

	return walk.ret;
}

static long vfio_pci_ioctl(void *device_data,
			   unsigned int cmd, unsigned long arg)
{
	struct vfio_pci_device *vdev = device_data;
	unsigned long minsz;

	if (cmd == VFIO_DEVICE_GET_INFO) {
		struct vfio_device_info info;

		minsz = offsetofend(struct vfio_device_info, num_irqs);

		if (copy_from_user(&info, (void __user *)arg, minsz))
			return -EFAULT;

		if (info.argsz < minsz)
			return -EINVAL;

		info.flags = VFIO_DEVICE_FLAGS_PCI;

		if (vdev->reset_works)
			info.flags |= VFIO_DEVICE_FLAGS_RESET;

		info.num_regions = VFIO_PCI_NUM_REGIONS;
		info.num_irqs = VFIO_PCI_NUM_IRQS;

		return copy_to_user((void __user *)arg, &info, minsz);

	} else if (cmd == VFIO_DEVICE_GET_REGION_INFO) {
		struct pci_dev *pdev = vdev->pdev;
		struct vfio_region_info info;

		minsz = offsetofend(struct vfio_region_info, offset);

		if (copy_from_user(&info, (void __user *)arg, minsz))
			return -EFAULT;

		if (info.argsz < minsz)
			return -EINVAL;

		switch (info.index) {
		case VFIO_PCI_CONFIG_REGION_INDEX:
			info.offset = VFIO_PCI_INDEX_TO_OFFSET(info.index);
			info.size = pdev->cfg_size;
			info.flags = VFIO_REGION_INFO_FLAG_READ |
				     VFIO_REGION_INFO_FLAG_WRITE;
			break;
		case VFIO_PCI_BAR0_REGION_INDEX ... VFIO_PCI_BAR5_REGION_INDEX:
			info.offset = VFIO_PCI_INDEX_TO_OFFSET(info.index);
			info.size = pci_resource_len(pdev, info.index);
			if (!info.size) {
				info.flags = 0;
				break;
			}

			info.flags = VFIO_REGION_INFO_FLAG_READ |
				     VFIO_REGION_INFO_FLAG_WRITE;
			if (IS_ENABLED(CONFIG_VFIO_PCI_MMAP) &&
			    pci_resource_flags(pdev, info.index) &
			    IORESOURCE_MEM && info.size >= PAGE_SIZE)
				info.flags |= VFIO_REGION_INFO_FLAG_MMAP;
			break;
		case VFIO_PCI_ROM_REGION_INDEX:
		{
			void __iomem *io;
			size_t size;

			info.offset = VFIO_PCI_INDEX_TO_OFFSET(info.index);
			info.flags = 0;

			/* Report the BAR size, not the ROM size */
			info.size = pci_resource_len(pdev, info.index);
			if (!info.size)
				break;

			/* Is it really there? */
			io = pci_map_rom(pdev, &size);
			if (!io || !size) {
				info.size = 0;
				break;
			}
			pci_unmap_rom(pdev, io);

			info.flags = VFIO_REGION_INFO_FLAG_READ;
			break;
		}
		case VFIO_PCI_VGA_REGION_INDEX:
			if (!vdev->has_vga)
				return -EINVAL;

			info.offset = VFIO_PCI_INDEX_TO_OFFSET(info.index);
			info.size = 0xc0000;
			info.flags = VFIO_REGION_INFO_FLAG_READ |
				     VFIO_REGION_INFO_FLAG_WRITE;

			break;
		default:
			return -EINVAL;
		}

		return copy_to_user((void __user *)arg, &info, minsz);

	} else if (cmd == VFIO_DEVICE_GET_IRQ_INFO) {
		struct vfio_irq_info info;

		minsz = offsetofend(struct vfio_irq_info, count);

		if (copy_from_user(&info, (void __user *)arg, minsz))
			return -EFAULT;

		if (info.argsz < minsz || info.index >= VFIO_PCI_NUM_IRQS)
			return -EINVAL;

		switch (info.index) {
		case VFIO_PCI_INTX_IRQ_INDEX ... VFIO_PCI_MSIX_IRQ_INDEX:
		case VFIO_PCI_REQ_IRQ_INDEX:
			break;
		case VFIO_PCI_ERR_IRQ_INDEX:
			if (pci_is_pcie(vdev->pdev))
				break;
		/* pass thru to return error */
		default:
			return -EINVAL;
		}

		info.flags = VFIO_IRQ_INFO_EVENTFD;

		info.count = vfio_pci_get_irq_count(vdev, info.index);

		if (info.index == VFIO_PCI_INTX_IRQ_INDEX)
			info.flags |= (VFIO_IRQ_INFO_MASKABLE |
				       VFIO_IRQ_INFO_AUTOMASKED);
		else
			info.flags |= VFIO_IRQ_INFO_NORESIZE;

		return copy_to_user((void __user *)arg, &info, minsz);

	} else if (cmd == VFIO_DEVICE_SET_IRQS) {
		struct vfio_irq_set hdr;
		u8 *data = NULL;
		int ret = 0;

		minsz = offsetofend(struct vfio_irq_set, count);

		if (copy_from_user(&hdr, (void __user *)arg, minsz))
			return -EFAULT;

		if (hdr.argsz < minsz || hdr.index >= VFIO_PCI_NUM_IRQS ||
		    hdr.flags & ~(VFIO_IRQ_SET_DATA_TYPE_MASK |
				  VFIO_IRQ_SET_ACTION_TYPE_MASK))
			return -EINVAL;

		if (!(hdr.flags & VFIO_IRQ_SET_DATA_NONE)) {
			size_t size;
			int max = vfio_pci_get_irq_count(vdev, hdr.index);

			if (hdr.flags & VFIO_IRQ_SET_DATA_BOOL)
				size = sizeof(uint8_t);
			else if (hdr.flags & VFIO_IRQ_SET_DATA_EVENTFD)
				size = sizeof(int32_t);
			else
				return -EINVAL;

			if (hdr.argsz - minsz < hdr.count * size ||
			    hdr.start >= max || hdr.start + hdr.count > max)
				return -EINVAL;

			data = memdup_user((void __user *)(arg + minsz),
					   hdr.count * size);
			if (IS_ERR(data))
				return PTR_ERR(data);
		}

		mutex_lock(&vdev->igate);

		ret = vfio_pci_set_irqs_ioctl(vdev, hdr.flags, hdr.index,
					      hdr.start, hdr.count, data);

		mutex_unlock(&vdev->igate);
		kfree(data);

		return ret;

	} else if (cmd == VFIO_DEVICE_RESET) {
		return vdev->reset_works ?
			pci_try_reset_function(vdev->pdev) : -EINVAL;

	} else if (cmd == VFIO_DEVICE_GET_PCI_HOT_RESET_INFO) {
		struct vfio_pci_hot_reset_info hdr;
		struct vfio_pci_fill_info fill = { 0 };
		struct vfio_pci_dependent_device *devices = NULL;
		bool slot = false;
		int ret = 0;

		minsz = offsetofend(struct vfio_pci_hot_reset_info, count);

		if (copy_from_user(&hdr, (void __user *)arg, minsz))
			return -EFAULT;

		if (hdr.argsz < minsz)
			return -EINVAL;

		hdr.flags = 0;

		/* Can we do a slot or bus reset or neither? */
		if (!pci_probe_reset_slot(vdev->pdev->slot))
			slot = true;
		else if (pci_probe_reset_bus(vdev->pdev->bus))
			return -ENODEV;

		/* How many devices are affected? */
		ret = vfio_pci_for_each_slot_or_bus(vdev->pdev,
						    vfio_pci_count_devs,
						    &fill.max, slot);
		if (ret)
			return ret;

		WARN_ON(!fill.max); /* Should always be at least one */

		/*
		 * If there's enough space, fill it now, otherwise return
		 * -ENOSPC and the number of devices affected.
		 */
		if (hdr.argsz < sizeof(hdr) + (fill.max * sizeof(*devices))) {
			ret = -ENOSPC;
			hdr.count = fill.max;
			goto reset_info_exit;
		}

		devices = kcalloc(fill.max, sizeof(*devices), GFP_KERNEL);
		if (!devices)
			return -ENOMEM;

		fill.devices = devices;

		ret = vfio_pci_for_each_slot_or_bus(vdev->pdev,
						    vfio_pci_fill_devs,
						    &fill, slot);

		/*
		 * If a device was removed between counting and filling,
		 * we may come up short of fill.max.  If a device was
		 * added, we'll have a return of -EAGAIN above.
		 */
		if (!ret)
			hdr.count = fill.cur;

reset_info_exit:
		if (copy_to_user((void __user *)arg, &hdr, minsz))
			ret = -EFAULT;

		if (!ret) {
			if (copy_to_user((void __user *)(arg + minsz), devices,
					 hdr.count * sizeof(*devices)))
				ret = -EFAULT;
		}

		kfree(devices);
		return ret;

	} else if (cmd == VFIO_DEVICE_PCI_HOT_RESET) {
		struct vfio_pci_hot_reset hdr;
		int32_t *group_fds;
		struct vfio_pci_group_entry *groups;
		struct vfio_pci_group_info info;
		bool slot = false;
		int i, count = 0, ret = 0;

		minsz = offsetofend(struct vfio_pci_hot_reset, count);

		if (copy_from_user(&hdr, (void __user *)arg, minsz))
			return -EFAULT;

		if (hdr.argsz < minsz || hdr.flags)
			return -EINVAL;

		/* Can we do a slot or bus reset or neither? */
		if (!pci_probe_reset_slot(vdev->pdev->slot))
			slot = true;
		else if (pci_probe_reset_bus(vdev->pdev->bus))
			return -ENODEV;

		/*
		 * We can't let userspace give us an arbitrarily large
		 * buffer to copy, so verify how many we think there
		 * could be.  Note groups can have multiple devices so
		 * one group per device is the max.
		 */
		ret = vfio_pci_for_each_slot_or_bus(vdev->pdev,
						    vfio_pci_count_devs,
						    &count, slot);
		if (ret)
			return ret;

		/* Somewhere between 1 and count is OK */
		if (!hdr.count || hdr.count > count)
			return -EINVAL;

		group_fds = kcalloc(hdr.count, sizeof(*group_fds), GFP_KERNEL);
		groups = kcalloc(hdr.count, sizeof(*groups), GFP_KERNEL);
		if (!group_fds || !groups) {
			kfree(group_fds);
			kfree(groups);
			return -ENOMEM;
		}

		if (copy_from_user(group_fds, (void __user *)(arg + minsz),
				   hdr.count * sizeof(*group_fds))) {
			kfree(group_fds);
			kfree(groups);
			return -EFAULT;
		}

		/*
		 * For each group_fd, get the group through the vfio external
		 * user interface and store the group and iommu ID.  This
		 * ensures the group is held across the reset.
		 */
		for (i = 0; i < hdr.count; i++) {
			struct vfio_group *group;
			struct fd f = fdget(group_fds[i]);
			if (!f.file) {
				ret = -EBADF;
				break;
			}

			group = vfio_group_get_external_user(f.file);
			fdput(f);
			if (IS_ERR(group)) {
				ret = PTR_ERR(group);
				break;
			}

			groups[i].group = group;
			groups[i].id = vfio_external_user_iommu_id(group);
		}

		kfree(group_fds);

		/* release reference to groups on error */
		if (ret)
			goto hot_reset_release;

		info.count = hdr.count;
		info.groups = groups;

		/*
		 * Test whether all the affected devices are contained
		 * by the set of groups provided by the user.
		 */
		ret = vfio_pci_for_each_slot_or_bus(vdev->pdev,
						    vfio_pci_validate_devs,
						    &info, slot);
		if (!ret)
			/* User has access, do the reset */
			ret = slot ? pci_try_reset_slot(vdev->pdev->slot) :
				     pci_try_reset_bus(vdev->pdev->bus);

hot_reset_release:
		for (i--; i >= 0; i--)
			vfio_group_put_external_user(groups[i].group);

		kfree(groups);
		return ret;
	}

	return -ENOTTY;
}

static ssize_t vfio_pci_rw(void *device_data, char __user *buf,
			   size_t count, loff_t *ppos, bool iswrite)
{
	unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
	struct vfio_pci_device *vdev = device_data;

	if (index >= VFIO_PCI_NUM_REGIONS)
		return -EINVAL;

	switch (index) {
	case VFIO_PCI_CONFIG_REGION_INDEX:
		return vfio_pci_config_rw(vdev, buf, count, ppos, iswrite);

	case VFIO_PCI_ROM_REGION_INDEX:
		if (iswrite)
			return -EINVAL;
		return vfio_pci_bar_rw(vdev, buf, count, ppos, false);

	case VFIO_PCI_BAR0_REGION_INDEX ... VFIO_PCI_BAR5_REGION_INDEX:
		return vfio_pci_bar_rw(vdev, buf, count, ppos, iswrite);

	case VFIO_PCI_VGA_REGION_INDEX:
		return vfio_pci_vga_rw(vdev, buf, count, ppos, iswrite);
	}

	return -EINVAL;
}

static ssize_t vfio_pci_read(void *device_data, char __user *buf,
			     size_t count, loff_t *ppos)
{
	if (!count)
		return 0;

	return vfio_pci_rw(device_data, buf, count, ppos, false);
}

static ssize_t vfio_pci_write(void *device_data, const char __user *buf,
			      size_t count, loff_t *ppos)
{
	if (!count)
		return 0;

	return vfio_pci_rw(device_data, (char __user *)buf, count, ppos, true);
}

static int vfio_pci_mmap(void *device_data, struct vm_area_struct *vma)
{
	struct vfio_pci_device *vdev = device_data;
	struct pci_dev *pdev = vdev->pdev;
	unsigned int index;
	u64 phys_len, req_len, pgoff, req_start;
	int ret;

	index = vma->vm_pgoff >> (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT);

	if (vma->vm_end < vma->vm_start)
		return -EINVAL;
	if ((vma->vm_flags & VM_SHARED) == 0)
		return -EINVAL;
	if (index >= VFIO_PCI_ROM_REGION_INDEX)
		return -EINVAL;
	if (!(pci_resource_flags(pdev, index) & IORESOURCE_MEM))
		return -EINVAL;

	phys_len = pci_resource_len(pdev, index);
	req_len = vma->vm_end - vma->vm_start;
	pgoff = vma->vm_pgoff &
		((1U << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - 1);
	req_start = pgoff << PAGE_SHIFT;

	if (phys_len < PAGE_SIZE || req_start + req_len > phys_len)
		return -EINVAL;

	if (index == vdev->msix_bar) {
		/*
		 * Disallow mmaps overlapping the MSI-X table; users don't
		 * get to touch this directly.  We could find somewhere
		 * else to map the overlap, but page granularity is only
		 * a recommendation, not a requirement, so the user needs
		 * to know which bits are real.  Requiring them to mmap
		 * around the table makes that clear.
		 */

		/* If neither entirely above nor below, then it overlaps */
		if (!(req_start >= vdev->msix_offset + vdev->msix_size ||
		      req_start + req_len <= vdev->msix_offset))
			return -EINVAL;
	}

	/*
	 * Even though we don't make use of the barmap for the mmap,
	 * we need to request the region and the barmap tracks that.
	 */
	if (!vdev->barmap[index]) {
		ret = pci_request_selected_regions(pdev,
						   1 << index, "vfio-pci");
		if (ret)
			return ret;

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

	vma->vm_private_data = vdev;
	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
	vma->vm_pgoff = (pci_resource_start(pdev, index) >> PAGE_SHIFT) + pgoff;

	return remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
			       req_len, vma->vm_page_prot);
}

static void vfio_pci_request(void *device_data, unsigned int count)
{
	struct vfio_pci_device *vdev = device_data;

	mutex_lock(&vdev->igate);

	if (vdev->req_trigger) {
		dev_dbg(&vdev->pdev->dev, "Requesting device from user\n");
		eventfd_signal(vdev->req_trigger, 1);
	}

	mutex_unlock(&vdev->igate);
}

static const struct vfio_device_ops vfio_pci_ops = {
	.name		= "vfio-pci",
	.open		= vfio_pci_open,
	.release	= vfio_pci_release,
	.ioctl		= vfio_pci_ioctl,
	.read		= vfio_pci_read,
	.write		= vfio_pci_write,
	.mmap		= vfio_pci_mmap,
	.request	= vfio_pci_request,
};

static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
{
	struct vfio_pci_device *vdev;
	struct iommu_group *group;
	int ret;

	if (pdev->hdr_type != PCI_HEADER_TYPE_NORMAL)
		return -EINVAL;

	group = iommu_group_get(&pdev->dev);
	if (!group)
		return -EINVAL;

	vdev = kzalloc(sizeof(*vdev), GFP_KERNEL);
	if (!vdev) {
		iommu_group_put(group);
		return -ENOMEM;
	}

	vdev->pdev = pdev;
	vdev->irq_type = VFIO_PCI_NUM_IRQS;
	mutex_init(&vdev->igate);
	spin_lock_init(&vdev->irqlock);

	ret = vfio_add_group_dev(&pdev->dev, &vfio_pci_ops, vdev);
	if (ret) {
		iommu_group_put(group);
		kfree(vdev);
	}

	if (vfio_pci_is_vga(pdev)) {
		vga_client_register(pdev, vdev, NULL, vfio_pci_set_vga_decode);
		vga_set_legacy_decoding(pdev,
					vfio_pci_set_vga_decode(vdev, false));
	}

	return ret;
}

static void vfio_pci_remove(struct pci_dev *pdev)
{
	struct vfio_pci_device *vdev;

	vdev = vfio_del_group_dev(&pdev->dev);
	if (!vdev)
		return;

	iommu_group_put(pdev->dev.iommu_group);
	kfree(vdev);

	if (vfio_pci_is_vga(pdev)) {
		vga_client_register(pdev, NULL, NULL, NULL);
		vga_set_legacy_decoding(pdev,
				VGA_RSRC_NORMAL_IO | VGA_RSRC_NORMAL_MEM |
				VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM);
	}
}

static pci_ers_result_t vfio_pci_aer_err_detected(struct pci_dev *pdev,
						  pci_channel_state_t state)
{
	struct vfio_pci_device *vdev;
	struct vfio_device *device;

	device = vfio_device_get_from_dev(&pdev->dev);
	if (device == NULL)
		return PCI_ERS_RESULT_DISCONNECT;

	vdev = vfio_device_data(device);
	if (vdev == NULL) {
		vfio_device_put(device);
		return PCI_ERS_RESULT_DISCONNECT;
	}

	mutex_lock(&vdev->igate);

	if (vdev->err_trigger)
		eventfd_signal(vdev->err_trigger, 1);

	mutex_unlock(&vdev->igate);

	vfio_device_put(device);

	return PCI_ERS_RESULT_CAN_RECOVER;
}

static struct pci_error_handlers vfio_err_handlers = {
	.error_detected = vfio_pci_aer_err_detected,
};

static struct pci_driver vfio_pci_driver = {
	.name		= "vfio-pci",
	.id_table	= NULL, /* only dynamic ids */
	.probe		= vfio_pci_probe,
	.remove		= vfio_pci_remove,
	.err_handler	= &vfio_err_handlers,
};

struct vfio_devices {
	struct vfio_device **devices;
	int cur_index;
	int max_index;
};

static int vfio_pci_get_devs(struct pci_dev *pdev, void *data)
{
	struct vfio_devices *devs = data;
	struct pci_driver *pci_drv = ACCESS_ONCE(pdev->driver);

	if (pci_drv != &vfio_pci_driver)
		return -EBUSY;

	if (devs->cur_index == devs->max_index)
		return -ENOSPC;

	devs->devices[devs->cur_index] = vfio_device_get_from_dev(&pdev->dev);
	if (!devs->devices[devs->cur_index])
		return -EINVAL;

	devs->cur_index++;
	return 0;
}

/*
 * Attempt to do a bus/slot reset if there are devices affected by a reset for
 * this device that are needs_reset and all of the affected devices are unused
 * (!refcnt).  Callers are required to hold driver_lock when calling this to
 * prevent device opens and concurrent bus reset attempts.  We prevent device
 * unbinds by acquiring and holding a reference to the vfio_device.
 *
 * NB: vfio-core considers a group to be viable even if some devices are
 * bound to drivers like pci-stub or pcieport.  Here we require all devices
 * to be bound to vfio_pci since that's the only way we can be sure they
 * stay put.
 */
static void vfio_pci_try_bus_reset(struct vfio_pci_device *vdev)
{
	struct vfio_devices devs = { .cur_index = 0 };
	int i = 0, ret = -EINVAL;
	bool needs_reset = false, slot = false;
	struct vfio_pci_device *tmp;

	if (!pci_probe_reset_slot(vdev->pdev->slot))
		slot = true;
	else if (pci_probe_reset_bus(vdev->pdev->bus))
		return;

	if (vfio_pci_for_each_slot_or_bus(vdev->pdev, vfio_pci_count_devs,
					  &i, slot) || !i)
		return;

	devs.max_index = i;
	devs.devices = kcalloc(i, sizeof(struct vfio_device *), GFP_KERNEL);
	if (!devs.devices)
		return;

	if (vfio_pci_for_each_slot_or_bus(vdev->pdev,
					  vfio_pci_get_devs, &devs, slot))
		goto put_devs;

	for (i = 0; i < devs.cur_index; i++) {
		tmp = vfio_device_data(devs.devices[i]);
		if (tmp->needs_reset)
			needs_reset = true;
		if (tmp->refcnt)
			goto put_devs;
	}

	if (needs_reset)
		ret = slot ? pci_try_reset_slot(vdev->pdev->slot) :
			     pci_try_reset_bus(vdev->pdev->bus);

put_devs:
	for (i = 0; i < devs.cur_index; i++) {
		if (!ret) {
			tmp = vfio_device_data(devs.devices[i]);
			tmp->needs_reset = false;
		}
		vfio_device_put(devs.devices[i]);
	}

	kfree(devs.devices);
}

static void __exit vfio_pci_cleanup(void)
{
	pci_unregister_driver(&vfio_pci_driver);
	vfio_pci_uninit_perm_bits();
}

static int __init vfio_pci_init(void)
{
	int ret;

	/* Allocate shared config space permision data used by all devices */
	ret = vfio_pci_init_perm_bits();
	if (ret)
		return ret;

	/* Register and scan for devices */
	ret = pci_register_driver(&vfio_pci_driver);
	if (ret)
		goto out_driver;

	return 0;

out_driver:
	vfio_pci_uninit_perm_bits();
	return ret;
}

module_init(vfio_pci_init);
module_exit(vfio_pci_cleanup);

MODULE_VERSION(DRIVER_VERSION);
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);