Merge tag 'vfio-for-v3.6' of git://github.com/awilliam/linux-vfio

		and kernel/power/user.c

'8'	all				SNP8023 advanced NIC card

					<mailto:mcr@solidum.com>

';'	64-7F	linux/vfio.h

'@'	00-0F	linux/radeonfb.h	conflict!

'@'	00-0F	drivers/video/aty/aty128fb.c	conflict!

'A'	00-1F	linux/apm_bios.h	conflict!

VFIO - "Virtual Function I/O"[1]

-------------------------------------------------------------------------------

Many modern system now provide DMA and interrupt remapping facilities

to help ensure I/O devices behave within the boundaries they've been

allotted.  This includes x86 hardware with AMD-Vi and Intel VT-d,

POWER systems with Partitionable Endpoints (PEs) and embedded PowerPC

systems such as Freescale PAMU.  The VFIO driver is an IOMMU/device

agnostic framework for exposing direct device access to userspace, in

a secure, IOMMU protected environment.  In other words, this allows

safe[2], non-privileged, userspace drivers.

Why do we want that?  Virtual machines often make use of direct device

access ("device assignment") when configured for the highest possible

I/O performance.  From a device and host perspective, this simply

turns the VM into a userspace driver, with the benefits of

significantly reduced latency, higher bandwidth, and direct use of

bare-metal device drivers[3].

Some applications, particularly in the high performance computing

field, also benefit from low-overhead, direct device access from

userspace.  Examples include network adapters (often non-TCP/IP based)

and compute accelerators.  Prior to VFIO, these drivers had to either

go through the full development cycle to become proper upstream

driver, be maintained out of tree, or make use of the UIO framework,

which has no notion of IOMMU protection, limited interrupt support,

and requires root privileges to access things like PCI configuration

space.

The VFIO driver framework intends to unify these, replacing both the

KVM PCI specific device assignment code as well as provide a more

secure, more featureful userspace driver environment than UIO.

Groups, Devices, and IOMMUs

-------------------------------------------------------------------------------

Devices are the main target of any I/O driver.  Devices typically

create a programming interface made up of I/O access, interrupts,

and DMA.  Without going into the details of each of these, DMA is

by far the most critical aspect for maintaining a secure environment

as allowing a device read-write access to system memory imposes the

greatest risk to the overall system integrity.

To help mitigate this risk, many modern IOMMUs now incorporate

isolation properties into what was, in many cases, an interface only

meant for translation (ie. solving the addressing problems of devices

with limited address spaces).  With this, devices can now be isolated

from each other and from arbitrary memory access, thus allowing

things like secure direct assignment of devices into virtual machines.

This isolation is not always at the granularity of a single device

though.  Even when an IOMMU is capable of this, properties of devices,

interconnects, and IOMMU topologies can each reduce this isolation.

For instance, an individual device may be part of a larger multi-

function enclosure.  While the IOMMU may be able to distinguish

between devices within the enclosure, the enclosure may not require

transactions between devices to reach the IOMMU.  Examples of this

could be anything from a multi-function PCI device with backdoors

between functions to a non-PCI-ACS (Access Control Services) capable

bridge allowing redirection without reaching the IOMMU.  Topology

can also play a factor in terms of hiding devices.  A PCIe-to-PCI

bridge masks the devices behind it, making transaction appear as if

from the bridge itself.  Obviously IOMMU design plays a major factor

as well.

Therefore, while for the most part an IOMMU may have device level

granularity, any system is susceptible to reduced granularity.  The

IOMMU API therefore supports a notion of IOMMU groups.  A group is

a set of devices which is isolatable from all other devices in the

system.  Groups are therefore the unit of ownership used by VFIO.

While the group is the minimum granularity that must be used to

ensure secure user access, it's not necessarily the preferred

granularity.  In IOMMUs which make use of page tables, it may be

possible to share a set of page tables between different groups,

reducing the overhead both to the platform (reduced TLB thrashing,

reduced duplicate page tables), and to the user (programming only

a single set of translations).  For this reason, VFIO makes use of

a container class, which may hold one or more groups.  A container

is created by simply opening the /dev/vfio/vfio character device.

On its own, the container provides little functionality, with all

but a couple version and extension query interfaces locked away.

The user needs to add a group into the container for the next level

of functionality.  To do this, the user first needs to identify the

group associated with the desired device.  This can be done using

the sysfs links described in the example below.  By unbinding the

device from the host driver and binding it to a VFIO driver, a new

VFIO group will appear for the group as /dev/vfio/$GROUP, where

$GROUP is the IOMMU group number of which the device is a member.

If the IOMMU group contains multiple devices, each will need to

be bound to a VFIO driver before operations on the VFIO group

are allowed (it's also sufficient to only unbind the device from

host drivers if a VFIO driver is unavailable; this will make the

group available, but not that particular device).  TBD - interface

for disabling driver probing/locking a device.

Once the group is ready, it may be added to the container by opening

the VFIO group character device (/dev/vfio/$GROUP) and using the

VFIO_GROUP_SET_CONTAINER ioctl, passing the file descriptor of the

previously opened container file.  If desired and if the IOMMU driver

supports sharing the IOMMU context between groups, multiple groups may

be set to the same container.  If a group fails to set to a container

with existing groups, a new empty container will need to be used

instead.

With a group (or groups) attached to a container, the remaining

ioctls become available, enabling access to the VFIO IOMMU interfaces.

Additionally, it now becomes possible to get file descriptors for each

device within a group using an ioctl on the VFIO group file descriptor.

The VFIO device API includes ioctls for describing the device, the I/O

regions and their read/write/mmap offsets on the device descriptor, as

well as mechanisms for describing and registering interrupt

notifications.

VFIO Usage Example

-------------------------------------------------------------------------------

Assume user wants to access PCI device 0000:06:0d.0

$ readlink /sys/bus/pci/devices/0000:06:0d.0/iommu_group

../../../../kernel/iommu_groups/26

This device is therefore in IOMMU group 26.  This device is on the

pci bus, therefore the user will make use of vfio-pci to manage the

group:

# modprobe vfio-pci

Binding this device to the vfio-pci driver creates the VFIO group

character devices for this group:

$ lspci -n -s 0000:06:0d.0

06:0d.0 0401: 1102:0002 (rev 08)

# echo 0000:06:0d.0 > /sys/bus/pci/devices/0000:06:0d.0/driver/unbind

# echo 1102 0002 > /sys/bus/pci/drivers/vfio/new_id

Now we need to look at what other devices are in the group to free

it for use by VFIO:

$ ls -l /sys/bus/pci/devices/0000:06:0d.0/iommu_group/devices

total 0

lrwxrwxrwx. 1 root root 0 Apr 23 16:13 0000:00:1e.0 ->

	../../../../devices/pci0000:00/0000:00:1e.0

lrwxrwxrwx. 1 root root 0 Apr 23 16:13 0000:06:0d.0 ->

	../../../../devices/pci0000:00/0000:00:1e.0/0000:06:0d.0

lrwxrwxrwx. 1 root root 0 Apr 23 16:13 0000:06:0d.1 ->

	../../../../devices/pci0000:00/0000:00:1e.0/0000:06:0d.1

This device is behind a PCIe-to-PCI bridge[4], therefore we also

need to add device 0000:06:0d.1 to the group following the same

procedure as above.  Device 0000:00:1e.0 is a bridge that does

not currently have a host driver, therefore it's not required to

bind this device to the vfio-pci driver (vfio-pci does not currently

support PCI bridges).

The final step is to provide the user with access to the group if

unprivileged operation is desired (note that /dev/vfio/vfio provides

no capabilities on its own and is therefore expected to be set to

mode 0666 by the system).

# chown user:user /dev/vfio/26

The user now has full access to all the devices and the iommu for this

group and can access them as follows:

	int container, group, device, i;

	struct vfio_group_status group_status =

					{ .argsz = sizeof(group_status) };

	struct vfio_iommu_x86_info iommu_info = { .argsz = sizeof(iommu_info) };

	struct vfio_iommu_x86_dma_map dma_map = { .argsz = sizeof(dma_map) };

	struct vfio_device_info device_info = { .argsz = sizeof(device_info) };

	/* Create a new container */

	container = open("/dev/vfio/vfio, O_RDWR);

	if (ioctl(container, VFIO_GET_API_VERSION) != VFIO_API_VERSION)

		/* Unknown API version */

	if (!ioctl(container, VFIO_CHECK_EXTENSION, VFIO_X86_IOMMU))

		/* Doesn't support the IOMMU driver we want. */

	/* Open the group */

	group = open("/dev/vfio/26", O_RDWR);

	/* Test the group is viable and available */

	ioctl(group, VFIO_GROUP_GET_STATUS, &group_status);

	if (!(group_status.flags & VFIO_GROUP_FLAGS_VIABLE))

		/* Group is not viable (ie, not all devices bound for vfio) */

	/* Add the group to the container */

	ioctl(group, VFIO_GROUP_SET_CONTAINER, &container);

	/* Enable the IOMMU model we want */

	ioctl(container, VFIO_SET_IOMMU, VFIO_X86_IOMMU)

	/* Get addition IOMMU info */

	ioctl(container, VFIO_IOMMU_GET_INFO, &iommu_info);

	/* Allocate some space and setup a DMA mapping */

	dma_map.vaddr = mmap(0, 1024 * 1024, PROT_READ | PROT_WRITE,

			     MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);

	dma_map.size = 1024 * 1024;

	dma_map.iova = 0; /* 1MB starting at 0x0 from device view */

	dma_map.flags = VFIO_DMA_MAP_FLAG_READ | VFIO_DMA_MAP_FLAG_WRITE;

	ioctl(container, VFIO_IOMMU_MAP_DMA, &dma_map);

	/* Get a file descriptor for the device */

	device = ioctl(group, VFIO_GROUP_GET_DEVICE_FD, "0000:06:0d.0");

	/* Test and setup the device */

	ioctl(device, VFIO_DEVICE_GET_INFO, &device_info);

	for (i = 0; i < device_info.num_regions; i++) {

		struct vfio_region_info reg = { .argsz = sizeof(reg) };

		reg.index = i;

		ioctl(device, VFIO_DEVICE_GET_REGION_INFO, &reg);

		/* Setup mappings... read/write offsets, mmaps

		 * For PCI devices, config space is a region */

	}

	for (i = 0; i < device_info.num_irqs; i++) {

		struct vfio_irq_info irq = { .argsz = sizeof(irq) };

		irq.index = i;

		ioctl(device, VFIO_DEVICE_GET_IRQ_INFO, &reg);

		/* Setup IRQs... eventfds, VFIO_DEVICE_SET_IRQS */

	}

	/* Gratuitous device reset and go... */

	ioctl(device, VFIO_DEVICE_RESET);

VFIO User API

-------------------------------------------------------------------------------

Please see include/linux/vfio.h for complete API documentation.

VFIO bus driver API

-------------------------------------------------------------------------------

VFIO bus drivers, such as vfio-pci make use of only a few interfaces

into VFIO core.  When devices are bound and unbound to the driver,

the driver should call vfio_add_group_dev() and vfio_del_group_dev()

respectively:

extern int vfio_add_group_dev(struct iommu_group *iommu_group,

                              struct device *dev,

                              const struct vfio_device_ops *ops,

                              void *device_data);

extern void *vfio_del_group_dev(struct device *dev);

vfio_add_group_dev() indicates to the core to begin tracking the

specified iommu_group and register the specified dev as owned by

a VFIO bus driver.  The driver provides an ops structure for callbacks

similar to a file operations structure:

struct vfio_device_ops {

	int	(*open)(void *device_data);

	void	(*release)(void *device_data);

	ssize_t	(*read)(void *device_data, char __user *buf,

			size_t count, loff_t *ppos);

	ssize_t	(*write)(void *device_data, const char __user *buf,

			 size_t size, loff_t *ppos);

	long	(*ioctl)(void *device_data, unsigned int cmd,

			 unsigned long arg);

	int	(*mmap)(void *device_data, struct vm_area_struct *vma);

};

Each function is passed the device_data that was originally registered

in the vfio_add_group_dev() call above.  This allows the bus driver

an easy place to store its opaque, private data.  The open/release

callbacks are issued when a new file descriptor is created for a

device (via VFIO_GROUP_GET_DEVICE_FD).  The ioctl interface provides

a direct pass through for VFIO_DEVICE_* ioctls.  The read/write/mmap

interfaces implement the device region access defined by the device's

own VFIO_DEVICE_GET_REGION_INFO ioctl.

-------------------------------------------------------------------------------

[1] VFIO was originally an acronym for "Virtual Function I/O" in its

initial implementation by Tom Lyon while as Cisco.  We've since

outgrown the acronym, but it's catchy.

[2] "safe" also depends upon a device being "well behaved".  It's

possible for multi-function devices to have backdoors between

functions and even for single function devices to have alternative

access to things like PCI config space through MMIO registers.  To

guard against the former we can include additional precautions in the

IOMMU driver to group multi-function PCI devices together

(iommu=group_mf).  The latter we can't prevent, but the IOMMU should

still provide isolation.  For PCI, SR-IOV Virtual Functions are the

best indicator of "well behaved", as these are designed for

virtualization usage models.

[3] As always there are trade-offs to virtual machine device

assignment that are beyond the scope of VFIO.  It's expected that

future IOMMU technologies will reduce some, but maybe not all, of

these trade-offs.

[4] In this case the device is below a PCI bridge, so transactions

from either function of the device are indistinguishable to the iommu:

-[0000:00]-+-1e.0-[06]--+-0d.0

                        \-0d.1

00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev 90)

F:	Documentation/filesystems/vfat.txt

F:	fs/fat/

VFIO DRIVER

M:	Alex Williamson <alex.williamson@redhat.com>

L:	kvm@vger.kernel.org

S:	Maintained

F:	Documentation/vfio.txt

F:	drivers/vfio/

F:	include/linux/vfio.h

VIDEOBUF2 FRAMEWORK

M:	Pawel Osciak <pawel@osciak.com>

M:	Marek Szyprowski <m.szyprowski@samsung.com>

source "drivers/uio/Kconfig"

source "drivers/vfio/Kconfig"

source "drivers/vlynq/Kconfig"

source "drivers/virtio/Kconfig"

obj-$(CONFIG_FUSION)		+= message/

obj-y				+= firewire/

obj-$(CONFIG_UIO)		+= uio/

obj-$(CONFIG_VFIO)		+= vfio/

obj-y				+= cdrom/

obj-y				+= auxdisplay/

obj-$(CONFIG_PCCARD)		+= pcmcia/