coalesced_mmio.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * KVM coalesced MMIO
  4 *
  5 * Copyright (c) 2008 Bull S.A.S.
  6 * Copyright 2009 Red Hat, Inc. and/or its affiliates.
  7 *
  8 *  Author: Laurent Vivier <Laurent.Vivier@bull.net>
  9 *
 10 */
 11
 12#include <kvm/iodev.h>
 13
 14#include <linux/kvm_host.h>
 15#include <linux/slab.h>
 16#include <linux/kvm.h>
 17
 18#include "coalesced_mmio.h"
 19
 20static inline struct kvm_coalesced_mmio_dev *to_mmio(struct kvm_io_device *dev)
 21{
 22	return container_of(dev, struct kvm_coalesced_mmio_dev, dev);
 23}
 24
 25static int coalesced_mmio_in_range(struct kvm_coalesced_mmio_dev *dev,
 26				   gpa_t addr, int len)
 27{
 28	/* is it in a batchable area ?
 29	 * (addr,len) is fully included in
 30	 * (zone->addr, zone->size)
 31	 */
 32	if (len < 0)
 33		return 0;
 34	if (addr + len < addr)
 35		return 0;
 36	if (addr < dev->zone.addr)
 37		return 0;
 38	if (addr + len > dev->zone.addr + dev->zone.size)
 39		return 0;
 40	return 1;
 41}
 42
 43static int coalesced_mmio_write(struct kvm_vcpu *vcpu,
 44				struct kvm_io_device *this, gpa_t addr,
 45				int len, const void *val)
 46{
 47	struct kvm_coalesced_mmio_dev *dev = to_mmio(this);
 48	struct kvm_coalesced_mmio_ring *ring = dev->kvm->coalesced_mmio_ring;
 49	__u32 insert;
 50
 51	if (!coalesced_mmio_in_range(dev, addr, len))
 52		return -EOPNOTSUPP;
 53
 54	spin_lock(&dev->kvm->ring_lock);
 55
 56	/*
 57	 * last is the index of the entry to fill.  Verify userspace hasn't
 58	 * set last to be out of range, and that there is room in the ring.
 59	 * Leave one entry free in the ring so that userspace can differentiate
 60	 * between an empty ring and a full ring.
 61	 */
 62	insert = READ_ONCE(ring->last);
 63	if (insert >= KVM_COALESCED_MMIO_MAX ||
 64	    (insert + 1) % KVM_COALESCED_MMIO_MAX == READ_ONCE(ring->first)) {
 65		spin_unlock(&dev->kvm->ring_lock);
 66		return -EOPNOTSUPP;
 67	}
 68
 69	/* copy data in first free entry of the ring */
 70
 71	ring->coalesced_mmio[insert].phys_addr = addr;
 72	ring->coalesced_mmio[insert].len = len;
 73	memcpy(ring->coalesced_mmio[insert].data, val, len);
 74	ring->coalesced_mmio[insert].pio = dev->zone.pio;
 75	smp_wmb();
 76	ring->last = (insert + 1) % KVM_COALESCED_MMIO_MAX;
 77	spin_unlock(&dev->kvm->ring_lock);
 78	return 0;
 79}
 80
 81static void coalesced_mmio_destructor(struct kvm_io_device *this)
 82{
 83	struct kvm_coalesced_mmio_dev *dev = to_mmio(this);
 84
 85	list_del(&dev->list);
 86
 87	kfree(dev);
 88}
 89
 90static const struct kvm_io_device_ops coalesced_mmio_ops = {
 91	.write      = coalesced_mmio_write,
 92	.destructor = coalesced_mmio_destructor,
 93};
 94
 95int kvm_coalesced_mmio_init(struct kvm *kvm)
 96{
 97	struct page *page;
 98
 99	page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
100	if (!page)
101		return -ENOMEM;
102
103	kvm->coalesced_mmio_ring = page_address(page);
104
105	/*
106	 * We're using this spinlock to sync access to the coalesced ring.
107	 * The list doesn't need its own lock since device registration and
108	 * unregistration should only happen when kvm->slots_lock is held.
109	 */
110	spin_lock_init(&kvm->ring_lock);
111	INIT_LIST_HEAD(&kvm->coalesced_zones);
112
113	return 0;
114}
115
116void kvm_coalesced_mmio_free(struct kvm *kvm)
117{
118	if (kvm->coalesced_mmio_ring)
119		free_page((unsigned long)kvm->coalesced_mmio_ring);
120}
121
122int kvm_vm_ioctl_register_coalesced_mmio(struct kvm *kvm,
123					 struct kvm_coalesced_mmio_zone *zone)
124{
125	int ret;
126	struct kvm_coalesced_mmio_dev *dev;
127
128	if (zone->pio != 1 && zone->pio != 0)
129		return -EINVAL;
130
131	dev = kzalloc(sizeof(struct kvm_coalesced_mmio_dev),
132		      GFP_KERNEL_ACCOUNT);
133	if (!dev)
134		return -ENOMEM;
135
136	kvm_iodevice_init(&dev->dev, &coalesced_mmio_ops);
137	dev->kvm = kvm;
138	dev->zone = *zone;
139
140	mutex_lock(&kvm->slots_lock);
141	ret = kvm_io_bus_register_dev(kvm,
142				zone->pio ? KVM_PIO_BUS : KVM_MMIO_BUS,
143				zone->addr, zone->size, &dev->dev);
144	if (ret < 0)
145		goto out_free_dev;
146	list_add_tail(&dev->list, &kvm->coalesced_zones);
147	mutex_unlock(&kvm->slots_lock);
148
149	return 0;
150
151out_free_dev:
152	mutex_unlock(&kvm->slots_lock);
153	kfree(dev);
154
155	return ret;
156}
157
158int kvm_vm_ioctl_unregister_coalesced_mmio(struct kvm *kvm,
159					   struct kvm_coalesced_mmio_zone *zone)
160{
161	struct kvm_coalesced_mmio_dev *dev, *tmp;
162	int r;
163
164	if (zone->pio != 1 && zone->pio != 0)
165		return -EINVAL;
166
167	mutex_lock(&kvm->slots_lock);
168
169	list_for_each_entry_safe(dev, tmp, &kvm->coalesced_zones, list) {
170		if (zone->pio == dev->zone.pio &&
171		    coalesced_mmio_in_range(dev, zone->addr, zone->size)) {
172			r = kvm_io_bus_unregister_dev(kvm,
173				zone->pio ? KVM_PIO_BUS : KVM_MMIO_BUS, &dev->dev);
174			/*
175			 * On failure, unregister destroys all devices on the
176			 * bus, including the target device. There's no need
177			 * to restart the walk as there aren't any zones left.
178			 */
179			if (r)
180				break;
181		}
182	}
183
184	mutex_unlock(&kvm->slots_lock);
185
186	/*
187	 * Ignore the result of kvm_io_bus_unregister_dev(), from userspace's
188	 * perspective, the coalesced MMIO is most definitely unregistered.
189	 */
190	return 0;
191}