virt/kvm/coalesced_mmio.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * KVM coalesced MMIO
0004  *
0005  * Copyright (c) 2008 Bull S.A.S.
0006  * Copyright 2009 Red Hat, Inc. and/or its affiliates.
0007  *
0008  *  Author: Laurent Vivier <Laurent.Vivier@bull.net>
0009  *
0010  */
0011
0012 #include <kvm/iodev.h>
0013
0014 #include <linux/kvm_host.h>
0015 #include <linux/slab.h>
0016 #include <linux/kvm.h>
0017
0018 #include "coalesced_mmio.h"
0019
0020 static inline struct kvm_coalesced_mmio_dev *to_mmio(struct kvm_io_device *dev)
0021 {
0022     return container_of(dev, struct kvm_coalesced_mmio_dev, dev);
0023 }
0024
0025 static int coalesced_mmio_in_range(struct kvm_coalesced_mmio_dev *dev,
0026                    gpa_t addr, int len)
0027 {
0028     /* is it in a batchable area ?
0029      * (addr,len) is fully included in
0030      * (zone->addr, zone->size)
0031      */
0032     if (len < 0)
0033         return 0;
0034     if (addr + len < addr)
0035         return 0;
0036     if (addr < dev->zone.addr)
0037         return 0;
0038     if (addr + len > dev->zone.addr + dev->zone.size)
0039         return 0;
0040     return 1;
0041 }
0042
0043 static int coalesced_mmio_has_room(struct kvm_coalesced_mmio_dev *dev, u32 last)
0044 {
0045     struct kvm_coalesced_mmio_ring *ring;
0046     unsigned avail;
0047
0048     /* Are we able to batch it ? */
0049
0050     /* last is the first free entry
0051      * check if we don't meet the first used entry
0052      * there is always one unused entry in the buffer
0053      */
0054     ring = dev->kvm->coalesced_mmio_ring;
0055     avail = (ring->first - last - 1) % KVM_COALESCED_MMIO_MAX;
0056     if (avail == 0) {
0057         /* full */
0058         return 0;
0059     }
0060
0061     return 1;
0062 }
0063
0064 static int coalesced_mmio_write(struct kvm_vcpu *vcpu,
0065                 struct kvm_io_device *this, gpa_t addr,
0066                 int len, const void *val)
0067 {
0068     struct kvm_coalesced_mmio_dev *dev = to_mmio(this);
0069     struct kvm_coalesced_mmio_ring *ring = dev->kvm->coalesced_mmio_ring;
0070     __u32 insert;
0071
0072     if (!coalesced_mmio_in_range(dev, addr, len))
0073         return -EOPNOTSUPP;
0074
0075     spin_lock(&dev->kvm->ring_lock);
0076
0077     insert = READ_ONCE(ring->last);
0078     if (!coalesced_mmio_has_room(dev, insert) ||
0079         insert >= KVM_COALESCED_MMIO_MAX) {
0080         spin_unlock(&dev->kvm->ring_lock);
0081         return -EOPNOTSUPP;
0082     }
0083
0084     /* copy data in first free entry of the ring */
0085
0086     ring->coalesced_mmio[insert].phys_addr = addr;
0087     ring->coalesced_mmio[insert].len = len;
0088     memcpy(ring->coalesced_mmio[insert].data, val, len);
0089     ring->coalesced_mmio[insert].pio = dev->zone.pio;
0090     smp_wmb();
0091     ring->last = (insert + 1) % KVM_COALESCED_MMIO_MAX;
0092     spin_unlock(&dev->kvm->ring_lock);
0093     return 0;
0094 }
0095
0096 static void coalesced_mmio_destructor(struct kvm_io_device *this)
0097 {
0098     struct kvm_coalesced_mmio_dev *dev = to_mmio(this);
0099
0100     list_del(&dev->list);
0101
0102     kfree(dev);
0103 }
0104
0105 static const struct kvm_io_device_ops coalesced_mmio_ops = {
0106     .write      = coalesced_mmio_write,
0107     .destructor = coalesced_mmio_destructor,
0108 };
0109
0110 int kvm_coalesced_mmio_init(struct kvm *kvm)
0111 {
0112     struct page *page;
0113
0114     page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
0115     if (!page)
0116         return -ENOMEM;
0117
0118     kvm->coalesced_mmio_ring = page_address(page);
0119
0120     /*
0121      * We're using this spinlock to sync access to the coalesced ring.
0122      * The list doesn't need its own lock since device registration and
0123      * unregistration should only happen when kvm->slots_lock is held.
0124      */
0125     spin_lock_init(&kvm->ring_lock);
0126     INIT_LIST_HEAD(&kvm->coalesced_zones);
0127
0128     return 0;
0129 }
0130
0131 void kvm_coalesced_mmio_free(struct kvm *kvm)
0132 {
0133     if (kvm->coalesced_mmio_ring)
0134         free_page((unsigned long)kvm->coalesced_mmio_ring);
0135 }
0136
0137 int kvm_vm_ioctl_register_coalesced_mmio(struct kvm *kvm,
0138                      struct kvm_coalesced_mmio_zone *zone)
0139 {
0140     int ret;
0141     struct kvm_coalesced_mmio_dev *dev;
0142
0143     if (zone->pio != 1 && zone->pio != 0)
0144         return -EINVAL;
0145
0146     dev = kzalloc(sizeof(struct kvm_coalesced_mmio_dev),
0147               GFP_KERNEL_ACCOUNT);
0148     if (!dev)
0149         return -ENOMEM;
0150
0151     kvm_iodevice_init(&dev->dev, &coalesced_mmio_ops);
0152     dev->kvm = kvm;
0153     dev->zone = *zone;
0154
0155     mutex_lock(&kvm->slots_lock);
0156     ret = kvm_io_bus_register_dev(kvm,
0157                 zone->pio ? KVM_PIO_BUS : KVM_MMIO_BUS,
0158                 zone->addr, zone->size, &dev->dev);
0159     if (ret < 0)
0160         goto out_free_dev;
0161     list_add_tail(&dev->list, &kvm->coalesced_zones);
0162     mutex_unlock(&kvm->slots_lock);
0163
0164     return 0;
0165
0166 out_free_dev:
0167     mutex_unlock(&kvm->slots_lock);
0168     kfree(dev);
0169
0170     return ret;
0171 }
0172
0173 int kvm_vm_ioctl_unregister_coalesced_mmio(struct kvm *kvm,
0174                        struct kvm_coalesced_mmio_zone *zone)
0175 {
0176     struct kvm_coalesced_mmio_dev *dev, *tmp;
0177     int r;
0178
0179     if (zone->pio != 1 && zone->pio != 0)
0180         return -EINVAL;
0181
0182     mutex_lock(&kvm->slots_lock);
0183
0184     list_for_each_entry_safe(dev, tmp, &kvm->coalesced_zones, list) {
0185         if (zone->pio == dev->zone.pio &&
0186             coalesced_mmio_in_range(dev, zone->addr, zone->size)) {
0187             r = kvm_io_bus_unregister_dev(kvm,
0188                 zone->pio ? KVM_PIO_BUS : KVM_MMIO_BUS, &dev->dev);
0189
0190             /*
0191              * On failure, unregister destroys all devices on the
0192              * bus _except_ the target device, i.e. coalesced_zones
0193              * has been modified.  No need to restart the walk as
0194              * there aren't any zones left.
0195              */
0196             if (r)
0197                 break;
0198             kvm_iodevice_destructor(&dev->dev);
0199         }
0200     }
0201
0202     mutex_unlock(&kvm->slots_lock);
0203
0204     /*
0205      * Ignore the result of kvm_io_bus_unregister_dev(), from userspace's
0206      * perspective, the coalesced MMIO is most definitely unregistered.
0207      */
0208     return 0;
0209 }