kvm: Add VFIO device

So far we've succeeded at making KVM and VFIO mostly unaware of each
other, but areas are cropping up where a connection beyond eventfds
and irqfds needs to be made.  This patch introduces a KVM-VFIO device
that is meant to be a gateway for such interaction.  The user creates
the device and can add and remove VFIO groups to it via file
descriptors.  When a group is added, KVM verifies the group is valid
and gets a reference to it via the VFIO external user interface.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/Documentation/virtual/kvm/devices/vfio.txt b/Documentation/virtual/kvm/devices/vfio.txt
new file mode 100644 (file)
index 0000000..ef51740
--- /dev/null
+++ b/Documentation/virtual/kvm/devices/vfio.txt
@@ -0,0 +1,22 @@
+VFIO virtual device
+===================
+
+Device types supported:
+  KVM_DEV_TYPE_VFIO
+
+Only one VFIO instance may be created per VM.  The created device
+tracks VFIO groups in use by the VM and features of those groups
+important to the correctness and acceleration of the VM.  As groups
+are enabled and disabled for use by the VM, KVM should be updated
+about their presence.  When registered with KVM, a reference to the
+VFIO-group is held by KVM.
+
+Groups:
+  KVM_DEV_VFIO_GROUP
+
+KVM_DEV_VFIO_GROUP attributes:
+  KVM_DEV_VFIO_GROUP_ADD: Add a VFIO group to VFIO-KVM device tracking
+  KVM_DEV_VFIO_GROUP_DEL: Remove a VFIO group from VFIO-KVM device tracking
+
+For each, kvm_device_attr.addr points to an int32_t file descriptor
+for the VFIO group.

diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index a47a3e5..b89c5db 100644 (file)
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -38,6 +38,7 @@ config KVM
        select PERF_EVENTS
        select HAVE_KVM_MSI
        select HAVE_KVM_CPU_RELAX_INTERCEPT
+       select KVM_VFIO
        ---help---
          Support hosting fully virtualized guest machines using hardware
          virtualization extensions.  You will need a fairly recent

diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
index bf4fb04..25d22b2 100644 (file)
--- a/arch/x86/kvm/Makefile
+++ b/arch/x86/kvm/Makefile
@@ -9,7 +9,7 @@ KVM := ../../../virt/kvm
 
 kvm-y                  += $(KVM)/kvm_main.o $(KVM)/ioapic.o \
                                $(KVM)/coalesced_mmio.o $(KVM)/irq_comm.o \
-                               $(KVM)/eventfd.o $(KVM)/irqchip.o
+                               $(KVM)/eventfd.o $(KVM)/irqchip.o $(KVM)/vfio.o
 kvm-$(CONFIG_KVM_DEVICE_ASSIGNMENT)    += $(KVM)/assigned-dev.o $(KVM)/iommu.o
 kvm-$(CONFIG_KVM_ASYNC_PF)     += $(KVM)/async_pf.o
 

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index c9d4236..7beddbd 100644 (file)
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1058,6 +1058,7 @@ struct kvm_device *kvm_device_from_filp(struct file *filp);
 
 extern struct kvm_device_ops kvm_mpic_ops;
 extern struct kvm_device_ops kvm_xics_ops;
+extern struct kvm_device_ops kvm_vfio_ops;
 
 #ifdef CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT
 

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 32c60b9..509cfbf 100644 (file)
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -845,6 +845,10 @@ struct kvm_device_attr {
 #define KVM_DEV_TYPE_FSL_MPIC_20       1
 #define KVM_DEV_TYPE_FSL_MPIC_42       2
 #define KVM_DEV_TYPE_XICS              3
+#define KVM_DEV_TYPE_VFIO              4
+#define  KVM_DEV_VFIO_GROUP                    1
+#define   KVM_DEV_VFIO_GROUP_ADD                       1
+#define   KVM_DEV_VFIO_GROUP_DEL                       2
 
 /*
  * ioctls for VM fds

diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
index 779262f..fbe1a48 100644 (file)
--- a/virt/kvm/Kconfig
+++ b/virt/kvm/Kconfig
@@ -27,3 +27,6 @@ config HAVE_KVM_MSI
 
 config HAVE_KVM_CPU_RELAX_INTERCEPT
        bool
+
+config KVM_VFIO
+       bool

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 9ca014d..82c4047 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2271,6 +2271,11 @@ static int kvm_ioctl_create_device(struct kvm *kvm,
                ops = &kvm_xics_ops;
                break;
 #endif
+#ifdef CONFIG_KVM_VFIO
+       case KVM_DEV_TYPE_VFIO:
+               ops = &kvm_vfio_ops;
+               break;
+#endif
        default:
                return -ENODEV;
        }

diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c
new file mode 100644 (file)
index 0000000..597c258
--- /dev/null
+++ b/virt/kvm/vfio.c
@@ -0,0 +1,220 @@
+/*
+ * 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>
+
+struct kvm_vfio_group {
+       struct list_head node;
+       struct vfio_group *vfio_group;
+};
+
+struct kvm_vfio {
+       struct list_head group_list;
+       struct mutex lock;
+};
+
+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 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;
+       void __user *argp = (void __user *)arg;
+       struct fd f;
+       int32_t fd;
+       int ret;
+
+       switch (attr) {
+       case KVM_DEV_VFIO_GROUP_ADD:
+               if (get_user(fd, (int32_t __user *)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;
+
+               mutex_unlock(&kv->lock);
+
+               return 0;
+
+       case KVM_DEV_VFIO_GROUP_DEL:
+               if (get_user(fd, (int32_t __user *)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;
+               }
+
+               mutex_unlock(&kv->lock);
+
+               kvm_vfio_group_put_external_user(vfio_group);
+
+               return ret;
+       }
+
+       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:
+                       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) {
+               kvm_vfio_group_put_external_user(kvg->vfio_group);
+               list_del(&kvg->node);
+               kfree(kvg);
+       }
+
+       kfree(kv);
+       kfree(dev); /* alloc by kvm_ioctl_create_device, free by .destroy */
+}
+
+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;
+}
+
+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,
+};