By using a Vec to hold the list of devices on the PciBus, there's a
problem when we use unplug. Indeed, the vector of devices gets reduced
and if the unplugged device was not the last one from the list, every
other device after this one is shifted on the bus.
To solve this problem, a HashMap is used. This allows to keep track of
the exact place where each device stands on the bus.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
The point of this new method is to let the caller decide when the
implementation of the PciDevice should free the BARs previously
allocated through the other method allocate_bars().
This provides a way to perform proper cleanup for any PCI device.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Upon removal of a PCI device, make sure we don't hold onto the device ID
as it could be reused for another device later.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
In order to handle the case where devices are very often plugged and
unplugged from a VM, we need to handle the PCI device ID allocation
better.
Any PCI device could be removed, which means we cannot simply rely on
the vector size to give the next available PCI device ID.
That's why this patch stores in memory the information about the 32
slots availability. Based on this information, whenever a new slot is
needed, the code can correctly provide an available ID, or simply return
an error because all slots are taken.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Simple function relying on the retain() method from std::Vec, allowing
to remove every occurence of the same device.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Now that the BusDevice devices are stored as Weak references by the IO
and MMIO buses, there's no need to use Weak references from the PciBus
anymore.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
We want to prevent from losing interrupts while they are masked. The
way they can be lost is due to the internals of how they are connected
through KVM. An eventfd is registered to a specific GSI, and then a
route is associated with this same GSI.
The current code adds/removes a route whenever a mask/unmask action
happens. Problem with this approach, KVM will consume the eventfd but
it won't be able to find an associated route and eventually it won't
be able to deliver the interrupt.
That's why this patch introduces a different way of masking/unmasking
the interrupts, simply by registering/unregistering the eventfd with the
GSI. This way, when the vector is masked, the eventfd is going to be
written but nothing will happen because KVM won't consume the event.
Whenever the unmask happens, the eventfd will be registered with a
specific GSI, and if there's some pending events, KVM will trigger them,
based on the route associated with the GSI.
Suggested-by: Liu Jiang <gerry@linux.alibaba.com>
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
We should not assume the offset produced by ECAM is identical to the
CONFIG_ADDRESS register of legacy PCI port io enumeration.
Signed-off-by: Qiu Wenbo <qiuwenbo@phytium.com.cn>
In order to anticipate the need to support more features related to the
access of a device's PCI config space, this commits changes the self
reference in the function read_config_register() to be mutable.
This also brings some more flexibility for any implementation of the
PciDevice trait.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Both InterruptDelivery and InterruptParameters can be removed from the
pci crate as they are not used anymore.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
There's no need for assign_irq() or assign_msix() functions from the
PciDevice trait, as we can see it's never used anywhere in the codebase.
That's why it's better to remove these methods from the trait, and
slightly adapt the existing code.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Now that KVM specific interrupts are handled through InterruptManager
trait implementation, the pci crate does not need to rely on kvm_ioctls
and kvm_bindings crates.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Based on all the previous changes, we can at this point replace the
entire interrupt management with the implementation of InterruptManager
and InterruptSourceGroup traits.
By using KvmInterruptManager from the DeviceManager, we can provide both
VirtioPciDevice and VfioPciDevice a way to pick the kind of
InterruptSourceGroup they want to create. Because they choose the type
of interrupt to be MSI/MSI-X, they will be given a MsiInterruptGroup.
Both MsixConfig and MsiConfig are responsible for the update of the GSI
routes, which is why, by passing the MsiInterruptGroup to them, they can
still perform the GSI route management without knowing implementation
details. That's where the InterruptSourceGroup is powerful, as it
provides a generic way to manage interrupt, no matter the type of
interrupt and no matter which hypervisor might be in use.
Once the full replacement has been achieved, both SystemAllocator and
KVM specific dependencies can be removed.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Callbacks are not the most Rust idiomatic way of programming. The right
way is to use a Trait to provide multiple implementation of the same
interface.
Additionally, a Trait will allow for multiple functions to be defined
while using callbacks means that a new callback must be introduced for
each new function we want to add.
For these two reasons, the current commit modifies the existing
VirtioInterrupt callback into a Trait of the same name.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
At this point, both MSI and MSI-X handle the KVM GSI routing update,
which means the vfio crate does not have to deal with it anymore.
Therefore, several functions can be removed from the vfio-pci code, as
they are not needed anymore.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Now that MsiConfig has access to both KVM VmFd and the list of GSI
routes, the update of the KVM GSI routes can be directly done from
MsiConfig instead of specifically from the vfio-pci implementation.
By moving the KVM GSI routes update at the MsiConfig level, any PCI
device such as vfio-pci, virtio-pci, or any other emulated PCI device
can benefit from it, without having to implement it on their own.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
The same way we have MsixConfig in charge of managing whatever relates
to MSI-X vectors, we need a MsiConfig structure to manage MSI vectors.
The MsiCap structure is still needed as a low level API, but it is now
part of the MsiConfig which oversees anything related to MSI.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
In order to factorize one step further, we let MsixConfig perform the
interrupt enabling/disabling. This is done by registering/unregistering
the KVM irq_fds of all GSI routes related to this device.
And now that MsixConfig is in charge of the irq_fds, vfio-pci must rely
on it to retrieve them and provide them to the vfio driver.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Now that MsixConfig has access to the irq_fd descriptors associated with
each vector, it can directly write to it anytime it needs to trigger an
interrupt.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Now that MsixConfig has access to both KVM VmFd and the list of GSI
routes, the update of the KVM GSI routes can be directly done from
MsixConfig instead of specifically from the vfio-pci implementation.
By moving the KVM GSI routes update at the MsixConfig level, both
vfio-pci and virtio-pci (or any other emulated PCI device) can benefit
from it, without having to implement it on their own.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Because MsixConfig will be responsible for updating KVM GSI routes at
some point, it is necessary that it can access the list of routes
contained by gsi_msi_routes.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Because MsixConfig will be responsible for updating the KVM GSI routes
at some point, it must have access to the VmFd to invoke the KVM ioctl
KVM_SET_GSI_ROUTING.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
The point here is to let MsixConfig take care of the GSI allocation,
which means the SystemAllocator must be passed from the vmm crate all
the way down to the pci crate.
Once this is done, the GSI allocation and irq_fd creation is performed
by MsixConfig directly.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
In order to anticipate the need for both msi.rs and msix.rs to rely on
some KVM utils and InterruptRoute structure to handle the update of the
KVM GSI routes, this commit adds these utilities directly to the pci
crate. So far, these were exclusively used by the vfio crate, which is
why there were located there.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
The current code was always considering 0xffffffff being written to the
register as a sign it was expecting to get the size, hence the BAR
reprogramming detection was stating this case was not a reprogramming
case.
Problem is, if the value 0xffffffff is directed at a 64bits BAR, this
might be the high or low part of a 64bits address which is meant to be
the new address of the BAR, which means we would miss the detection of
the BAR being reprogrammed here.
This commit improves the code using finer granularity checks in order to
detect this corner case correctly.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
The expansion ROM BAR reprogramming was being triggered for the wrong
reason and was causing the following error to be reported:
ERROR:pci/src/bus.rs:207 -- Failed moving device BAR: failed allocating
new 32 bits MMIO range
Following the PCI specification, here is what is defined:
Device independent configuration software can determine how much address
space the device requires by writing a value of all 1's to the address
portion of the register and then reading the value back.
This means we cannot expect 0xffffffff to be written, as the address
portion corresponds to the bits 31-11. That's why whenever the size of
this special BAR is being asked for, the value being written is
0xfffff800.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
The signal handling for vCPU signals has changed in the latest release
so switch to the new API.
Signed-off-by: Rob Bradford <robert.bradford@intel.com>
If the MSG_CTL is being written from a 32 bits write access, the offset
won't be 0x2, but 0x0 instead. That's simply because 32 bits access have
to be aligned on each double word.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Since the kvm crates now depend on vmm-sys-util, the bump must be
atomic.
The kvm-bindings and ioctls 0.2.0 and 0.4.0 crates come with a few API
changes, one of them being the use of a kvm_ioctls specific error type.
Porting our code to that type makes for a fairly large diff stat.
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
We need to rely on the latest kvm-ioctls version to benefit from the
recent addition of unregister_ioevent(), allowing us to detach a
previously registered eventfd to a PIO or MMIO guest address.
Because of this update, we had to modify the current constraint we had
on the vmm-sys-util crate, using ">= 0.1.1" instead of being strictly
tied to "0.2.0".
Once the dependency conflict resolved, this commit took care of fixing
build issues caused by recent modification of kvm-ioctls relying on
EventFd reference instead of RawFd.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
The specific part of PCI BAR reprogramming that happens for a virtio PCI
device is the update of the ioeventfds addresses KVM should listen to.
This should not be triggered for every BAR reprogramming associated with
the virtio device since a virtio PCI device might have multiple BARs.
The update of the ioeventfds addresses should only happen when the BAR
related to those addresses is being moved.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
The PciDevice trait is supposed to describe only functions related to
PCI. The specific method ioeventfds() has nothing to do with PCI, but
instead would be more specific to virtio transport devices.
This commit removes the ioeventfds() method from the PciDevice trait,
adding some convenient helper as_any() to retrieve the Any trait from
the structure behing the PciDevice trait. This is the only way to keep
calling into ioeventfds() function from VirtioPciDevice, so that we can
still properly reprogram the PCI BAR.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Storing a strong reference to the AddressManager behind the
DeviceRelocation trait results in a cyclic reference count.
Use a weak reference to break that dependency.
Signed-off-by: Rob Bradford <robert.bradford@intel.com>
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Based on the value being written to the BAR, the implementation can
now detect if the BAR is being moved to another address. If that is the
case, it invokes move_bar() function from the DeviceRelocation trait.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
In order to trigger the PCI BAR reprogramming from PciConfigIo and
PciConfigMmmio, we need the PciBus to have a hold onto the trait
implementation of DeviceRelocation.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Based on the type of BAR, we can now provide the correct address related
to a BAR index provided by the caller.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
In order to support PCI BAR reprogramming, the PciDevice trait defines a
new method move_bar() dedicated for taking appropriate action when a BAR
is moved to a different guest address.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
This new trait will allow the VMM to implement the mechanism following a
BAR modification regarding its location in the guest address space.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
This commit is the glue between the virtio-pci devices attached to the
vIOMMU, and the IORT ACPI table exposing them to the guest as sitting
behind this vIOMMU.
An important thing is the trait implementation provided to the virtio
vrings for each device attached to the vIOMMU, as they need to perform
proper address translation before they can access the buffers.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Refactor the PCI datastructures to move the device ownership to a PciBus
struct. This PciBus struct can then be used by both a PciConfigIo and
PciConfigMmio in order to expose the configuration space via both IO
port and also via MMIO for PCI MMCONFIG.
Signed-off-by: Rob Bradford <robert.bradford@intel.com>
Latest clippy version complains about our existing code for the
following reasons:
- trait objects without an explicit `dyn` are deprecated
- `...` range patterns are deprecated
- lint `clippy::const_static_lifetime` has been renamed to
`clippy::redundant_static_lifetimes`
- unnecessary `unsafe` block
- unneeded return statement
All these issues have been fixed through this patch, and rustfmt has
been run to cleanup potential formatting errors due to those changes.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
In order to check if device's interrupts are enabled, this patch adds
a helper function to the MsixConfig structure so that at any point in
time we can check if an interrupt should be delivered or not.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
The vector control offset is at the 4th byte of each MSI-X table entry.
For that reason, it is located at 0xc, and not 0x10 as implemented.
This commit fixes the current MSI-X code, allowing proper reading and
writing of each vector control register in the MSI-X table.
Fixes#156
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
The structure provided to the add_capability() function should only
contain what comes after the capability ID and the next capability
pointer, which are located on the first WORD.
Because the structure TestCap included _vndr and _next fields, they
were directly set after the first WORD, while the assertion was
expecting to find the values of len and foo fields.
Fixes#105
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
The structure of the vmm-sys-util crate has changed with lots of code
moving to submodules.
This change adjusts the use of the imported structs to reference the
submodules.
Fixes: #145
Signed-off-by: Rob Bradford <robert.bradford@intel.com>
Update all dependencies with "cargo upgrade" with the exception of
vmm-sys-utils which needs some extra porting work.
Signed-off-by: Rob Bradford <robert.bradford@intel.com>
The offsets returned by the table_offset() and pba_offset() function
were wrong as they were shifting the value by 3 bits. The MSI-X spec
defines the MSI-X table and PBA offsets as being defined on 3-31 bits,
but this does not mean it has to be shifted. Instead, the address is
still on 32 bits and assumes the LSB bits 0-2 are set to 0.
VFIO was working fine with devices were the MSI-X offset were 0x0, but
the bug was found on a device where the offset was non-null.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
The expansion ROM BAR can be considered like a 32-bit memory BAR with a
slight difference regarding the amount of reserved bits at the beginning
of its 32-bit value. Bit 0 indicates if the BAR is enabled or disabled,
while bits 1-10 are reserved. The remaining upper 21 bits hold the BAR
address.
This commit extends the pci crate in order to support expansion ROM BAR.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Every PCI device is exposed as a separate device, on a specific PCI
slot, and we explicitely don't support to expose a device as a multi
function device. For this reason, this patch makes sure the enumeration
of the PCI bus will not find some multi function device.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
The check performed on the end address was wrong since the end address
was actually the address right after the end. To get the right end
address, we need to add (region size - 1) to the start address.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
This patch adds the support for both IO and Memory BARs by expecting
the function allocate_bars() to identify the type of each BAR.
Based on the type, register_mapping() insert the address range on the
appropriate bus (PIO or MMIO).
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
The way the function write_reg() was implemented, it was not keeping
the bits supposed to be read-only whenever the guest was writing to one
of those. That's why this commit takes care of protecting those bits,
preventing them from being updated.
The tricky part is about the BARs since we also need to handle the very
specific case where the BAR is being written with all 1's. In that case
we want to return the size of the BAR instead of its address.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
A BAR can be three different types: IO, 32 bits Memory, or 64 bits
Memory. The VMM needs a way to set the right type depending on its
needs.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
In order to support use cases that require MSI, the pci crate is
being expanded with the description of an MSI PCI capability
structure through the new MsiCap Rust structure.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
This commit enhances the current msi-x code hosted in the pci crate
in order to be reused by the vfio crate. Specifically, it creates
several useful methods for the MsixCap structure that can simplify
the caller's code.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
PciConfigIo is a legacy pci bus dispatcher, which manages all pci
devices including a pci root bridge. However, it is unnecessary to
design a complex hierarchy which redirects every access by PciRoot.
Since pci root bridge is also a pci device instance, and only contains
easy config space read/write, and PciConfigIo actually acts as a pci bus
to dispatch resource based resolving when VMExit, we re-arrange to make
the pci hierarchy clean.
Signed-off-by: Jing Liu <jing2.liu@linux.intel.com>
When reading from or writing to a PCI BAR to handle a VM exit, we need
to have the BAR address itself to be able to support multiple BARs PCI
devices.
Fixes: #87
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
With the range base for the IO/MMIO vm exit address, a device with
multiple ranges has all the needed information for resolving which of
its range the exit is coming from
Fixes: #87
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
BusDevice includes two methods which are only for PCI devices, which should
be as members of PciDevice trait for a better clean high level APIs.
Signed-off-by: Jing Liu <jing2.liu@linux.intel.com>
As mentioned in the PCI specification, the Function Mask from the
Message Control Register can be set to prevent a device from injecting
MSI-X messages. This supersedes the vector masking as it interacts at
the device level.
Here quoted from the specification:
For MSI and MSI-X, while a vector is masked, the function is prohibited
from sending the associated message, and the function must set the
associated Pending bit whenever the function would otherwise send the
message. When software unmasks a vector whose associated Pending bit is
set, the function must schedule sending the associated message, and
clear the Pending bit as soon as the message has been sent. Note that
clearing the MSI-X Function Mask bit may result in many messages
needing to be sent.
This commit implements the behavior described above by reorganizing
the way the PCI configuration space is being written. It is indeed
important to be able to catch a change in the Message Control
Register without having to implement it for every PciDevice
implementation. Instead, the PciConfiguration has been modified to
take care of handling any update made to this register.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
The current MSI-X implementation completely ignores the values found
in the Vector Control register related to a specific vector, and never
updates the Pending Bit Array.
According to the PCI specification, MSI-X vectors can be masked
through the Vector Control register on bit 0. If this bit is set,
the device should not inject any MSI message. When the device
runs into such situation, it must not inject the interrupt, but
instead it must update the bit corresponding to the vector number
in the Pending Bit Array.
Later on, if/when the Vector Control register is updated, and if
the bit 0 is flipped from 0 to 1, the device must look into the PBA
to find out if there was a pending interrupt for this specific
vector. If that's the case, an MSI message is injected and the
bit from the PBA is cleared.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
As mentioned in the PCI specification, MSI-X table supports both
DWORD and QWORD accesses:
For all accesses to MSI-X Table and MSI-X PBA fields, software must
use aligned full DWORD or aligned full QWORD transactions; otherwise,
the result is undefined.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
In order to factorize the complexity brought by closures, this commit
merges IrqClosure and MsixClosure into a generic InterruptDelivery one.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
In order to allow virtio-pci devices to use MSI-X messages instead
of legacy pin based interrupts, this patch implements the MSI-X
support for cloud-hypervisor. The VMM code and virtio-pci bits have
been modified based on the "msix" module previously added to the pci
crate.
Fixes#12
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
In order to have access to the newly added signal_msi() function
from the kvm-ioctls crate, this commit updates the version of the
kvm-ioctls to the latest one.
Because set_user_memory_region() has been swtiched to "unsafe", we
also need to handle this small change in our cloud-hypervisor code
directly.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
In order to support MSI-X, this commit adds to the pci crate a new
module called "msix". This module brings all the necessary pieces
to let any PCI device implement MSI-X support.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Because we cannot always assume the irq fd will be the way to send
an IRQ to the guest, this means we cannot make the assumption that
every virtio device implementation should expect an EventFd to
trigger an IRQ.
This commit organizes the code related to virtio devices so that it
now expects a Rust closure instead of a known EventFd. This lets the
caller decide what should be done whenever a device needs to trigger
an interrupt to the guest.
The closure will allow for other type of interrupt mechanism such as
MSI to be implemented. From the device perspective, it could be a
pin based interrupt or an MSI, it does not matter since the device
will simply call into the provided callback, passing the appropriate
Queue as a reference. This design keeps the device model generic.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Add the BSD and Apache license.
Make all crosvm references point to the BSD license.
Add the right copyrights and identifier to our VMM code.
Add Intel copyright to the vm-virtio and pci crates.
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
After the virtio-blk device support has been introduced in the
previous commit, the vmm need to rely on this new device to boot
from disk images instead of initrd built into the kernel.
In order to achieve the proper support of virtio-blk, this commit
had to handle a few things:
- Register an ioevent fd for each virtqueue. This important to be
notified from the virtio driver that something has been written
on the queue.
- Fix the retrieval of 64bits BAR address. This is needed to provide
the right address which need to be registered as the notification
address from the virtio driver.
- Fix the write_bar and read_bar functions. They were both assuming
to be provided with an address, from which they were trying to
find the associated offset. But the reality is that the offset is
directly provided by the Bus layer.
- Register a new virtio-blk device as a virtio-pci device from the
vm.rs code. When the VM is started, it expects a block device to
be created, using this block device as the VM rootfs.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
This crate is based on the crosvm devices/src/pci implementation from 107edb3e
We introduced a few changes:
- This one is a standalone crate. The device crate does not carry any
PCI specific bits.
- Simplified PCI root configuration. We only carry a pointer to a
PciConfiguration, not a wrapper around it.
- Simplified BAR allocation API. All BARs from the PciDevice instance
must be generated at once through the PciDevice.allocate_bars()
method.
- The PCI BARs are added to the MMIO bus from the PciRoot add_device()
method.
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
