vfio.c

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// SPDX-License-Identifier: GPL-2.0-only
/*
 * VFIO-KVM bridge pseudo device
 *
 * Copyright (C) 2013 Red Hat, Inc.  All rights reserved.
 *     Author: Alex Williamson <alex.williamson@redhat.com>
 */
 
#include <linux/errno.h>
#include <linux/file.h>
#include <linux/kvm_host.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/vfio.h>
#include "vfio.h"
 
#ifdef CONFIG_SPAPR_TCE_IOMMU
#include <asm/kvm_ppc.h>
#endif
 
struct kvm_vfio_file {
    struct list_head node;
    struct file *file;
#ifdef CONFIG_SPAPR_TCE_IOMMU
    struct iommu_group *iommu_group;
#endif
};
 
struct kvm_vfio {
    struct list_head file_list;
    struct mutex lock;
    bool noncoherent;
};
 
static void kvm_vfio_file_set_kvm(struct file *file, struct kvm *kvm)
{
    void (*fn)(struct file *file, struct kvm *kvm);
 
    fn = symbol_get(vfio_file_set_kvm);
    if (!fn)
        return;
 
    fn(file, kvm);
 
    symbol_put(vfio_file_set_kvm);
}
 
static bool kvm_vfio_file_enforced_coherent(struct file *file)
{
    bool (*fn)(struct file *file);
    bool ret;
 
    fn = symbol_get(vfio_file_enforced_coherent);
    if (!fn)
        return false;
 
    ret = fn(file);
 
    symbol_put(vfio_file_enforced_coherent);
 
    return ret;
}
 
static bool kvm_vfio_file_is_valid(struct file *file)
{
    bool (*fn)(struct file *file);
    bool ret;
 
    fn = symbol_get(vfio_file_is_valid);
    if (!fn)
        return false;
 
    ret = fn(file);
 
    symbol_put(vfio_file_is_valid);
 
    return ret;
}
 
#ifdef CONFIG_SPAPR_TCE_IOMMU
static struct iommu_group *kvm_vfio_file_iommu_group(struct file *file)
{
    struct iommu_group *(*fn)(struct file *file);
    struct iommu_group *ret;
 
    fn = symbol_get(vfio_file_iommu_group);
    if (!fn)
        return NULL;
 
    ret = fn(file);
 
    symbol_put(vfio_file_iommu_group);
 
    return ret;
}
 
static void kvm_spapr_tce_release_vfio_group(struct kvm *kvm,
                         struct kvm_vfio_file *kvf)
{
    if (WARN_ON_ONCE(!kvf->iommu_group))
        return;
 
    kvm_spapr_tce_release_iommu_group(kvm, kvf->iommu_group);
    iommu_group_put(kvf->iommu_group);
    kvf->iommu_group = NULL;
}
#endif
 
/*
 * Groups/devices can use the same or different IOMMU domains. If the same
 * then adding a new group/device may change the coherency of groups/devices
 * we've previously been told about. We don't want to care about any of
 * that so we retest each group/device and bail as soon as we find one that's
 * noncoherent.  This means we only ever [un]register_noncoherent_dma once
 * for the whole device.
 */
static void kvm_vfio_update_coherency(struct kvm_device *dev)
{
    struct kvm_vfio *kv = dev->private;
    bool noncoherent = false;
    struct kvm_vfio_file *kvf;
 
    list_for_each_entry(kvf, &kv->file_list, node) {
        if (!kvm_vfio_file_enforced_coherent(kvf->file)) {
            noncoherent = true;
            break;
        }
    }
 
    if (noncoherent != kv->noncoherent) {
        kv->noncoherent = noncoherent;
 
        if (kv->noncoherent)
            kvm_arch_register_noncoherent_dma(dev->kvm);
        else
            kvm_arch_unregister_noncoherent_dma(dev->kvm);
    }
}
 
static int kvm_vfio_file_add(struct kvm_device *dev, unsigned int fd)
{
    struct kvm_vfio *kv = dev->private;
    struct kvm_vfio_file *kvf;
    struct file *filp;
    int ret = 0;
 
    filp = fget(fd);
    if (!filp)
        return -EBADF;
 
    /* Ensure the FD is a vfio FD. */
    if (!kvm_vfio_file_is_valid(filp)) {
        ret = -EINVAL;
        goto out_fput;
    }
 
    mutex_lock(&kv->lock);
 
    list_for_each_entry(kvf, &kv->file_list, node) {
        if (kvf->file == filp) {
            ret = -EEXIST;
            goto out_unlock;
        }
    }
 
    kvf = kzalloc(sizeof(*kvf), GFP_KERNEL_ACCOUNT);
    if (!kvf) {
        ret = -ENOMEM;
        goto out_unlock;
    }
 
    kvf->file = get_file(filp);
    list_add_tail(&kvf->node, &kv->file_list);
 
    kvm_arch_start_assignment(dev->kvm);
    kvm_vfio_file_set_kvm(kvf->file, dev->kvm);
    kvm_vfio_update_coherency(dev);
 
out_unlock:
    mutex_unlock(&kv->lock);
out_fput:
    fput(filp);
    return ret;
}
 
static int kvm_vfio_file_del(struct kvm_device *dev, unsigned int fd)
{
    struct kvm_vfio *kv = dev->private;
    struct kvm_vfio_file *kvf;
    struct fd f;
    int ret;
 
    f = fdget(fd);
    if (!f.file)
        return -EBADF;
 
    ret = -ENOENT;
 
    mutex_lock(&kv->lock);
 
    list_for_each_entry(kvf, &kv->file_list, node) {
        if (kvf->file != f.file)
            continue;
 
        list_del(&kvf->node);
        kvm_arch_end_assignment(dev->kvm);
#ifdef CONFIG_SPAPR_TCE_IOMMU
        kvm_spapr_tce_release_vfio_group(dev->kvm, kvf);
#endif
        kvm_vfio_file_set_kvm(kvf->file, NULL);
        fput(kvf->file);
        kfree(kvf);
        ret = 0;
        break;
    }
 
    kvm_vfio_update_coherency(dev);
 
    mutex_unlock(&kv->lock);
 
    fdput(f);
 
    return ret;
}
 
#ifdef CONFIG_SPAPR_TCE_IOMMU
static int kvm_vfio_file_set_spapr_tce(struct kvm_device *dev,
                       void __user *arg)
{
    struct kvm_vfio_spapr_tce param;
    struct kvm_vfio *kv = dev->private;
    struct kvm_vfio_file *kvf;
    struct fd f;
    int ret;
 
    if (copy_from_user(&param, arg, sizeof(struct kvm_vfio_spapr_tce)))
        return -EFAULT;
 
    f = fdget(param.groupfd);
    if (!f.file)
        return -EBADF;
 
    ret = -ENOENT;
 
    mutex_lock(&kv->lock);
 
    list_for_each_entry(kvf, &kv->file_list, node) {
        if (kvf->file != f.file)
            continue;
 
        if (!kvf->iommu_group) {
            kvf->iommu_group = kvm_vfio_file_iommu_group(kvf->file);
            if (WARN_ON_ONCE(!kvf->iommu_group)) {
                ret = -EIO;
                goto err_fdput;
            }
        }
 
        ret = kvm_spapr_tce_attach_iommu_group(dev->kvm, param.tablefd,
                               kvf->iommu_group);
        break;
    }
 
err_fdput:
    mutex_unlock(&kv->lock);
    fdput(f);
    return ret;
}
#endif
 
static int kvm_vfio_set_file(struct kvm_device *dev, long attr,
                 void __user *arg)
{
    int32_t __user *argp = arg;
    int32_t fd;
 
    switch (attr) {
    case KVM_DEV_VFIO_FILE_ADD:
        if (get_user(fd, argp))
            return -EFAULT;
        return kvm_vfio_file_add(dev, fd);
 
    case KVM_DEV_VFIO_FILE_DEL:
        if (get_user(fd, argp))
            return -EFAULT;
        return kvm_vfio_file_del(dev, fd);
 
#ifdef CONFIG_SPAPR_TCE_IOMMU
    case KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE:
        return kvm_vfio_file_set_spapr_tce(dev, arg);
#endif
    }
 
    return -ENXIO;
}
 
static int kvm_vfio_set_attr(struct kvm_device *dev,
                 struct kvm_device_attr *attr)
{
    switch (attr->group) {
    case KVM_DEV_VFIO_FILE:
        return kvm_vfio_set_file(dev, attr->attr,
                     u64_to_user_ptr(attr->addr));
    }
 
    return -ENXIO;
}
 
static int kvm_vfio_has_attr(struct kvm_device *dev,
                 struct kvm_device_attr *attr)
{
    switch (attr->group) {
    case KVM_DEV_VFIO_FILE:
        switch (attr->attr) {
        case KVM_DEV_VFIO_FILE_ADD:
        case KVM_DEV_VFIO_FILE_DEL:
#ifdef CONFIG_SPAPR_TCE_IOMMU
        case KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE:
#endif
            return 0;
        }
 
        break;
    }
 
    return -ENXIO;
}
 
static void kvm_vfio_release(struct kvm_device *dev)
{
    struct kvm_vfio *kv = dev->private;
    struct kvm_vfio_file *kvf, *tmp;
 
    list_for_each_entry_safe(kvf, tmp, &kv->file_list, node) {
#ifdef CONFIG_SPAPR_TCE_IOMMU
        kvm_spapr_tce_release_vfio_group(dev->kvm, kvf);
#endif
        kvm_vfio_file_set_kvm(kvf->file, NULL);
        fput(kvf->file);
        list_del(&kvf->node);
        kfree(kvf);
        kvm_arch_end_assignment(dev->kvm);
    }
 
    kvm_vfio_update_coherency(dev);
 
    kfree(kv);
    kfree(dev); /* alloc by kvm_ioctl_create_device, free by .release */
}
 
static int kvm_vfio_create(struct kvm_device *dev, u32 type);
 
static struct kvm_device_ops kvm_vfio_ops = {
    .name = "kvm-vfio",
    .create = kvm_vfio_create,
    .release = kvm_vfio_release,
    .set_attr = kvm_vfio_set_attr,
    .has_attr = kvm_vfio_has_attr,
};
 
static int kvm_vfio_create(struct kvm_device *dev, u32 type)
{
    struct kvm_device *tmp;
    struct kvm_vfio *kv;
 
    /* Only one VFIO "device" per VM */
    list_for_each_entry(tmp, &dev->kvm->devices, vm_node)
        if (tmp->ops == &kvm_vfio_ops)
            return -EBUSY;
 
    kv = kzalloc(sizeof(*kv), GFP_KERNEL_ACCOUNT);
    if (!kv)
        return -ENOMEM;
 
    INIT_LIST_HEAD(&kv->file_list);
    mutex_init(&kv->lock);
 
    dev->private = kv;
 
    return 0;
}
 
int kvm_vfio_ops_init(void)
{
    return kvm_register_device_ops(&kvm_vfio_ops, KVM_DEV_TYPE_VFIO);
}
 
void kvm_vfio_ops_exit(void)
{
    kvm_unregister_device_ops(KVM_DEV_TYPE_VFIO);
}