linux/virt/kvm/vfio.c
Alexey Kardashevskiy 121f80ba68 KVM: PPC: VFIO: Add in-kernel acceleration for VFIO
This allows the host kernel to handle H_PUT_TCE, H_PUT_TCE_INDIRECT
and H_STUFF_TCE requests targeted an IOMMU TCE table used for VFIO
without passing them to user space which saves time on switching
to user space and back.

This adds H_PUT_TCE/H_PUT_TCE_INDIRECT/H_STUFF_TCE handlers to KVM.
KVM tries to handle a TCE request in the real mode, if failed
it passes the request to the virtual mode to complete the operation.
If it a virtual mode handler fails, the request is passed to
the user space; this is not expected to happen though.

To avoid dealing with page use counters (which is tricky in real mode),
this only accelerates SPAPR TCE IOMMU v2 clients which are required
to pre-register the userspace memory. The very first TCE request will
be handled in the VFIO SPAPR TCE driver anyway as the userspace view
of the TCE table (iommu_table::it_userspace) is not allocated till
the very first mapping happens and we cannot call vmalloc in real mode.

If we fail to update a hardware IOMMU table unexpected reason, we just
clear it and move on as there is nothing really we can do about it -
for example, if we hot plug a VFIO device to a guest, existing TCE tables
will be mirrored automatically to the hardware and there is no interface
to report to the guest about possible failures.

This adds new attribute - KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE - to
the VFIO KVM device. It takes a VFIO group fd and SPAPR TCE table fd
and associates a physical IOMMU table with the SPAPR TCE table (which
is a guest view of the hardware IOMMU table). The iommu_table object
is cached and referenced so we do not have to look up for it in real mode.

This does not implement the UNSET counterpart as there is no use for it -
once the acceleration is enabled, the existing userspace won't
disable it unless a VFIO container is destroyed; this adds necessary
cleanup to the KVM_DEV_VFIO_GROUP_DEL handler.

This advertises the new KVM_CAP_SPAPR_TCE_VFIO capability to the user
space.

This adds real mode version of WARN_ON_ONCE() as the generic version
causes problems with rcu_sched. Since we testing what vmalloc_to_phys()
returns in the code, this also adds a check for already existing
vmalloc_to_phys() call in kvmppc_rm_h_put_tce_indirect().

This finally makes use of vfio_external_user_iommu_id() which was
introduced quite some time ago and was considered for removal.

Tests show that this patch increases transmission speed from 220MB/s
to 750..1020MB/s on 10Gb network (Chelsea CXGB3 10Gb ethernet card).

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
2017-04-20 11:39:26 +10:00

419 lines
8.7 KiB
C

/*
* VFIO-KVM bridge pseudo device
*
* Copyright (C) 2013 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.
*/
#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_group {
struct list_head node;
struct vfio_group *vfio_group;
};
struct kvm_vfio {
struct list_head group_list;
struct mutex lock;
bool noncoherent;
};
static struct vfio_group *kvm_vfio_group_get_external_user(struct file *filep)
{
struct vfio_group *vfio_group;
struct vfio_group *(*fn)(struct file *);
fn = symbol_get(vfio_group_get_external_user);
if (!fn)
return ERR_PTR(-EINVAL);
vfio_group = fn(filep);
symbol_put(vfio_group_get_external_user);
return vfio_group;
}
static void kvm_vfio_group_put_external_user(struct vfio_group *vfio_group)
{
void (*fn)(struct vfio_group *);
fn = symbol_get(vfio_group_put_external_user);
if (!fn)
return;
fn(vfio_group);
symbol_put(vfio_group_put_external_user);
}
static void kvm_vfio_group_set_kvm(struct vfio_group *group, struct kvm *kvm)
{
void (*fn)(struct vfio_group *, struct kvm *);
fn = symbol_get(vfio_group_set_kvm);
if (!fn)
return;
fn(group, kvm);
symbol_put(vfio_group_set_kvm);
}
static bool kvm_vfio_group_is_coherent(struct vfio_group *vfio_group)
{
long (*fn)(struct vfio_group *, unsigned long);
long ret;
fn = symbol_get(vfio_external_check_extension);
if (!fn)
return false;
ret = fn(vfio_group, VFIO_DMA_CC_IOMMU);
symbol_put(vfio_external_check_extension);
return ret > 0;
}
#ifdef CONFIG_SPAPR_TCE_IOMMU
static int kvm_vfio_external_user_iommu_id(struct vfio_group *vfio_group)
{
int (*fn)(struct vfio_group *);
int ret = -EINVAL;
fn = symbol_get(vfio_external_user_iommu_id);
if (!fn)
return ret;
ret = fn(vfio_group);
symbol_put(vfio_external_user_iommu_id);
return ret;
}
static struct iommu_group *kvm_vfio_group_get_iommu_group(
struct vfio_group *group)
{
int group_id = kvm_vfio_external_user_iommu_id(group);
if (group_id < 0)
return NULL;
return iommu_group_get_by_id(group_id);
}
static void kvm_spapr_tce_release_vfio_group(struct kvm *kvm,
struct vfio_group *vfio_group)
{
struct iommu_group *grp = kvm_vfio_group_get_iommu_group(vfio_group);
if (WARN_ON_ONCE(!grp))
return;
kvm_spapr_tce_release_iommu_group(kvm, grp);
iommu_group_put(grp);
}
#endif
/*
* Groups can use the same or different IOMMU domains. If the same then
* adding a new group may change the coherency of groups we've previously
* been told about. We don't want to care about any of that so we retest
* each group 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_group *kvg;
mutex_lock(&kv->lock);
list_for_each_entry(kvg, &kv->group_list, node) {
if (!kvm_vfio_group_is_coherent(kvg->vfio_group)) {
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);
}
mutex_unlock(&kv->lock);
}
static int kvm_vfio_set_group(struct kvm_device *dev, long attr, u64 arg)
{
struct kvm_vfio *kv = dev->private;
struct vfio_group *vfio_group;
struct kvm_vfio_group *kvg;
int32_t __user *argp = (int32_t __user *)(unsigned long)arg;
struct fd f;
int32_t fd;
int ret;
switch (attr) {
case KVM_DEV_VFIO_GROUP_ADD:
if (get_user(fd, argp))
return -EFAULT;
f = fdget(fd);
if (!f.file)
return -EBADF;
vfio_group = kvm_vfio_group_get_external_user(f.file);
fdput(f);
if (IS_ERR(vfio_group))
return PTR_ERR(vfio_group);
mutex_lock(&kv->lock);
list_for_each_entry(kvg, &kv->group_list, node) {
if (kvg->vfio_group == vfio_group) {
mutex_unlock(&kv->lock);
kvm_vfio_group_put_external_user(vfio_group);
return -EEXIST;
}
}
kvg = kzalloc(sizeof(*kvg), GFP_KERNEL);
if (!kvg) {
mutex_unlock(&kv->lock);
kvm_vfio_group_put_external_user(vfio_group);
return -ENOMEM;
}
list_add_tail(&kvg->node, &kv->group_list);
kvg->vfio_group = vfio_group;
kvm_arch_start_assignment(dev->kvm);
mutex_unlock(&kv->lock);
kvm_vfio_group_set_kvm(vfio_group, dev->kvm);
kvm_vfio_update_coherency(dev);
return 0;
case KVM_DEV_VFIO_GROUP_DEL:
if (get_user(fd, argp))
return -EFAULT;
f = fdget(fd);
if (!f.file)
return -EBADF;
vfio_group = kvm_vfio_group_get_external_user(f.file);
fdput(f);
if (IS_ERR(vfio_group))
return PTR_ERR(vfio_group);
ret = -ENOENT;
mutex_lock(&kv->lock);
list_for_each_entry(kvg, &kv->group_list, node) {
if (kvg->vfio_group != vfio_group)
continue;
list_del(&kvg->node);
kvm_vfio_group_put_external_user(kvg->vfio_group);
kfree(kvg);
ret = 0;
break;
}
kvm_arch_end_assignment(dev->kvm);
mutex_unlock(&kv->lock);
#ifdef CONFIG_SPAPR_TCE_IOMMU
kvm_spapr_tce_release_vfio_group(dev->kvm, vfio_group);
#endif
kvm_vfio_group_set_kvm(vfio_group, NULL);
kvm_vfio_group_put_external_user(vfio_group);
kvm_vfio_update_coherency(dev);
return ret;
#ifdef CONFIG_SPAPR_TCE_IOMMU
case KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE: {
struct kvm_vfio_spapr_tce param;
struct kvm_vfio *kv = dev->private;
struct vfio_group *vfio_group;
struct kvm_vfio_group *kvg;
struct fd f;
struct iommu_group *grp;
if (copy_from_user(&param, (void __user *)arg,
sizeof(struct kvm_vfio_spapr_tce)))
return -EFAULT;
f = fdget(param.groupfd);
if (!f.file)
return -EBADF;
vfio_group = kvm_vfio_group_get_external_user(f.file);
fdput(f);
if (IS_ERR(vfio_group))
return PTR_ERR(vfio_group);
grp = kvm_vfio_group_get_iommu_group(vfio_group);
if (WARN_ON_ONCE(!grp)) {
kvm_vfio_group_put_external_user(vfio_group);
return -EIO;
}
ret = -ENOENT;
mutex_lock(&kv->lock);
list_for_each_entry(kvg, &kv->group_list, node) {
if (kvg->vfio_group != vfio_group)
continue;
ret = kvm_spapr_tce_attach_iommu_group(dev->kvm,
param.tablefd, grp);
break;
}
mutex_unlock(&kv->lock);
iommu_group_put(grp);
kvm_vfio_group_put_external_user(vfio_group);
return ret;
}
#endif /* CONFIG_SPAPR_TCE_IOMMU */
}
return -ENXIO;
}
static int kvm_vfio_set_attr(struct kvm_device *dev,
struct kvm_device_attr *attr)
{
switch (attr->group) {
case KVM_DEV_VFIO_GROUP:
return kvm_vfio_set_group(dev, attr->attr, 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_GROUP:
switch (attr->attr) {
case KVM_DEV_VFIO_GROUP_ADD:
case KVM_DEV_VFIO_GROUP_DEL:
#ifdef CONFIG_SPAPR_TCE_IOMMU
case KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE:
#endif
return 0;
}
break;
}
return -ENXIO;
}
static void kvm_vfio_destroy(struct kvm_device *dev)
{
struct kvm_vfio *kv = dev->private;
struct kvm_vfio_group *kvg, *tmp;
list_for_each_entry_safe(kvg, tmp, &kv->group_list, node) {
#ifdef CONFIG_SPAPR_TCE_IOMMU
kvm_spapr_tce_release_vfio_group(dev->kvm, kvg->vfio_group);
#endif
kvm_vfio_group_set_kvm(kvg->vfio_group, NULL);
kvm_vfio_group_put_external_user(kvg->vfio_group);
list_del(&kvg->node);
kfree(kvg);
kvm_arch_end_assignment(dev->kvm);
}
kvm_vfio_update_coherency(dev);
kfree(kv);
kfree(dev); /* alloc by kvm_ioctl_create_device, free by .destroy */
}
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,
.destroy = kvm_vfio_destroy,
.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);
if (!kv)
return -ENOMEM;
INIT_LIST_HEAD(&kv->group_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);
}