// SPDX-License-Identifier: GPL-2.0

  /*
   * KVM coalesced MMIO
   *
   * Copyright (c) 2008 Bull S.A.S.

   * Copyright 2009 Red Hat, Inc. and/or its affiliates.

   *
   *  Author: Laurent Vivier <Laurent.Vivier@bull.net>
   *
   */

  #include <kvm/iodev.h>

  
  #include <linux/kvm_host.h>

  #include <linux/slab.h>

  #include <linux/kvm.h>
  
  #include "coalesced_mmio.h"

  static inline struct kvm_coalesced_mmio_dev *to_mmio(struct kvm_io_device *dev)
  {
  	return container_of(dev, struct kvm_coalesced_mmio_dev, dev);
  }

  static int coalesced_mmio_in_range(struct kvm_coalesced_mmio_dev *dev,
  				   gpa_t addr, int len)

  {

  	/* is it in a batchable area ?
  	 * (addr,len) is fully included in
  	 * (zone->addr, zone->size)
  	 */

  	if (len < 0)
  		return 0;
  	if (addr + len < addr)
  		return 0;
  	if (addr < dev->zone.addr)
  		return 0;
  	if (addr + len > dev->zone.addr + dev->zone.size)
  		return 0;
  	return 1;

  }

  static int coalesced_mmio_has_room(struct kvm_coalesced_mmio_dev *dev)
  {
  	struct kvm_coalesced_mmio_ring *ring;
  	unsigned avail;
  
  	/* Are we able to batch it ? */
  
  	/* last is the first free entry
  	 * check if we don't meet the first used entry
  	 * there is always one unused entry in the buffer
  	 */
  	ring = dev->kvm->coalesced_mmio_ring;
  	avail = (ring->first - ring->last - 1) % KVM_COALESCED_MMIO_MAX;
  	if (avail == 0) {
  		/* full */
  		return 0;
  	}
  
  	return 1;
  }

  static int coalesced_mmio_write(struct kvm_vcpu *vcpu,
  				struct kvm_io_device *this, gpa_t addr,
  				int len, const void *val)

  {

  	struct kvm_coalesced_mmio_dev *dev = to_mmio(this);

  	struct kvm_coalesced_mmio_ring *ring = dev->kvm->coalesced_mmio_ring;

  	if (!coalesced_mmio_in_range(dev, addr, len))
  		return -EOPNOTSUPP;

  	spin_lock(&dev->kvm->ring_lock);

  	if (!coalesced_mmio_has_room(dev)) {

  		spin_unlock(&dev->kvm->ring_lock);

  		return -EOPNOTSUPP;
  	}

  	/* copy data in first free entry of the ring */
  
  	ring->coalesced_mmio[ring->last].phys_addr = addr;
  	ring->coalesced_mmio[ring->last].len = len;
  	memcpy(ring->coalesced_mmio[ring->last].data, val, len);
  	smp_wmb();
  	ring->last = (ring->last + 1) % KVM_COALESCED_MMIO_MAX;

  	spin_unlock(&dev->kvm->ring_lock);

  	return 0;

  }
  
  static void coalesced_mmio_destructor(struct kvm_io_device *this)
  {

  	struct kvm_coalesced_mmio_dev *dev = to_mmio(this);

  	list_del(&dev->list);

  	kfree(dev);

  }

  static const struct kvm_io_device_ops coalesced_mmio_ops = {
  	.write      = coalesced_mmio_write,

  	.destructor = coalesced_mmio_destructor,
  };

  int kvm_coalesced_mmio_init(struct kvm *kvm)
  {

  	struct page *page;

  	int ret;

  	ret = -ENOMEM;
  	page = alloc_page(GFP_KERNEL | __GFP_ZERO);
  	if (!page)
  		goto out_err;

  	ret = 0;
  	kvm->coalesced_mmio_ring = page_address(page);

  	/*
  	 * We're using this spinlock to sync access to the coalesced ring.
  	 * The list doesn't need it's own lock since device registration and
  	 * unregistration should only happen when kvm->slots_lock is held.
  	 */
  	spin_lock_init(&kvm->ring_lock);
  	INIT_LIST_HEAD(&kvm->coalesced_zones);

  out_err:

  	return ret;

  }

  void kvm_coalesced_mmio_free(struct kvm *kvm)
  {
  	if (kvm->coalesced_mmio_ring)
  		free_page((unsigned long)kvm->coalesced_mmio_ring);
  }

  int kvm_vm_ioctl_register_coalesced_mmio(struct kvm *kvm,

  					 struct kvm_coalesced_mmio_zone *zone)

  {

  	int ret;
  	struct kvm_coalesced_mmio_dev *dev;

  	dev = kzalloc(sizeof(struct kvm_coalesced_mmio_dev), GFP_KERNEL);
  	if (!dev)
  		return -ENOMEM;
  
  	kvm_iodevice_init(&dev->dev, &coalesced_mmio_ops);
  	dev->kvm = kvm;
  	dev->zone = *zone;

  	mutex_lock(&kvm->slots_lock);

  	ret = kvm_io_bus_register_dev(kvm, KVM_MMIO_BUS, zone->addr,
  				      zone->size, &dev->dev);

  	if (ret < 0)
  		goto out_free_dev;
  	list_add_tail(&dev->list, &kvm->coalesced_zones);
  	mutex_unlock(&kvm->slots_lock);

  	return 0;

  out_free_dev:

  	mutex_unlock(&kvm->slots_lock);

  	kfree(dev);

  	return ret;

  }
  
  int kvm_vm_ioctl_unregister_coalesced_mmio(struct kvm *kvm,
  					   struct kvm_coalesced_mmio_zone *zone)
  {

  	struct kvm_coalesced_mmio_dev *dev, *tmp;

  	mutex_lock(&kvm->slots_lock);

  	list_for_each_entry_safe(dev, tmp, &kvm->coalesced_zones, list)
  		if (coalesced_mmio_in_range(dev, zone->addr, zone->size)) {
  			kvm_io_bus_unregister_dev(kvm, KVM_MMIO_BUS, &dev->dev);
  			kvm_iodevice_destructor(&dev->dev);

  		}

  	mutex_unlock(&kvm->slots_lock);

  
  	return 0;
  }