Instead of returning an `EventFd` type, which will actually force us to
clone the file descriptor in the Firecracker side.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

This is code we are not going to use in Firecracker. Remove it, so we
can keep the crates we vend as minimal as possible, including only
things we are actually using.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

We'd like to be able to store Vm within an atomic reference so we can
pass it around and share it with other components. The main issue with
doing this change is that we need Vm to be `mut` during initialization
and the builder.rs code was creating Vmm with Vm embedded in it.

To solve this, we break down the initialization of the Vmm object. We
first create its individual parts (Vm, Kvm and DeviceManager), perform
any necessary initialization logic on Vm and once this done add it
within an Arc.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

Add logic to track the device interrupts used by the microVM. This is
not strictly needed right now, but we will need it when adding support
for MSI-X interrupts. MSI-X interrupts are configured at runtime and we
need to interact with KVM to set the interruput routes. To do it, we
need to keep track all of the interrupts the VM is using.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

Enable Vm to vend and manage MSI/MSI-X interrupts. This adds the logic
to create a set of MSI vectors and then handle their lifetime.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

Vm object is now maintaining information about the interrupts (both
traditional IRQs and MSI-X vectors) that are being used by microVM
devices. Derive Serialize/Deserialize add logic for recreating objects
for relevant types.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

Commit d8c2714 (refactor: use VirtioInterrupt in VirtIO devices) which
refactored devices to use new VirtioInterrupt type introduced a bug
with the index used to trigger a queue interrupt. Instead of using the
actual queue index, we were using the index of the used descriptor.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

Apparently, PCI needs Queue::size to be initialized to the maximum
possible size supported by the device, otherwise initialization fails.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

Remove the flags in FADT that were declaring we do not support MSI and
PCI ASPM.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

Merge the device-related errors that DeviceManager might return. This
way, we can avoid adding yet another error type for PCI devices and
reduce some the variants of StartMicrovmError.

Suggested-by: Egor Lazarchuk <yegorlz@amazon.co.uk>
Signed-off-by: Babis Chalios <bchalios@amazon.es>

Add a VirtIO PCI transport implementation. When a Firecracker microVM is
launched with --enable-pci, we will create all VirtIO devices using the
PCI transport layer. Snapshotting of VirtIO PCI devices is not supported
and we will add this functionality in later commit.

Add a couple of tests that ensure that PCI configuration space is what
expected. We read common fields and make sure the BAR we allocate for
the VirtIO device is what expected.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

We are now calling KVM_CHECK_EXTENSION for checking the
KVM_CAP_MSI_DEVID capability. We are also calling KVM_SET_GSI_ROUTING to
set the interrupts routes and KVM_IRQFD to set/unset interrupt lines.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

Add some unit tests to PciSegment. We now test that the
next_device_bdf() method and the initialization logic work as expected.
We also check that the configuration space of the PCI segment is
correctly registered with the MMIO and, on x86, PIO bus.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

vm-allocator now allows us to (De)serialize IdAllocator and
AddressAllocator types. Add ResourceAllocator in DeviceManager snapshot
state and restore it when loading a snapshot. Like this we can avoid
doing the ExactMatch allocations during snapshot resumes for reserving
the exact same MMIO ranges.

Moreover, change DeviceManager and PciDevices to provide save/restore
functionality via the Persist trait. Like that we can avoid first
creating the objects and then restoring their state, overwriting their
fields.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

VirtIO MMIO restore logic activates the device the moment we restore the
device state, if the device was activated when snapshotted. Move the
activation responsibility to the logic the restores the MMIO transport.
The reason for this change is that that's how it will be done for the
PCI transport. Unifying this will allow us reusing the same types for
restoring the non-transport state of devices.

Note that we needed to change the way Net devices are saved/restored.
RxBuffer type of Net devices holds RX descriptors that we have parsed
from the Queue ahead of time. The way we restored this info was
manipulating the queue to re-parse the RX descriptors during the restore
phase. However, we need the device to be activated to do so, which now
isn't. So, instead of storing this info inside the snapshot make sure we
have flushed everything before taking the snapshot.

Also, simplify a bit the types that we use for serializing/deserializing
the state of a device.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

Support serializing the device-specific and transport state of a VirtIO
device that uses the PCI transport.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

ResourceAllocator object was part of DeviceManager since it is (mainly)
devices that use it. ResourceAllocator is as well the object that
implements (in a dummy way, for the moment) the DeviceRelocation trait
which PciDevices use to move the address space of a PciDevice when
triggered from the guest.

Problem with DeviceRelocation is that it also needs the Vm file
descriptor to perform the relocation, because we need to move register
the new IO event fd for VirtIO devices.

To make things simpler, move ResourceAllocator inside the Vm object. In
subsequent commit we will remove the DeviceRelocation from
ResourceAllocator and move it to Vm instead.

This has the nice secondary effect that we were able to simplify the
signature of many device-related methods that received Vm and
ResourceAllocator arguments.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

We had previously added MMIO and Port IO buses inside ResourceAllocator
so that we could implement DeviceRelocation for the type. Now, we will
delegate device relocation responsibilities to ArchVm instead. That is
because device relocation requires access to the Vm file descriptor as
well.

As a result, we can move buses to the Vm object itself. Add MMIO bus to
VmCommon as both architectures use it. Add PortIO bus for x86
architecture only.

Not that we don't still support DeviceRelocation. VirtIO devices should
not request us to relocate them. Also, for adding such support we would
need to also support VirtIO reset. We will look into adding this
functionaliyt later on.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

Add support for ITS device which provides support for MSI interrupts on
ARM architecture. This is currently supported only on systems with GICv3
interrupt controller.

In order to make saving/restore of ITS state work properly, we need to
change the order in which we restore redistributor register GICR_CTLR.
We need to make sure that this register is restored last. Otherwise,
restoring GICR_PROPBASER doesn't have any effect and ITS depends on it
in order to save/restore ITS tables to/from guest memory.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

Refactor the test code that inserts VirtIO devices in a Vmm object and
then add a test which creates a Vmm with PCI devices and then serializes
and deserializes the device manager and ensures that everything is as
restored as expected.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

Use pci_enabled fixture for boot time, block, and network tests to
create PCI microVM variants as well.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

We only pass pci=off if PCI is disabled in Firecracker. Adapt tests and
comments to reflect that.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

So that we don't have to downcast VirtioDevice trait objects to the
actual device type before calling the logic to process events for each
device.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

Instead of storing internal allocators of ResourceAllocator within an
Arc<Mutex<>> container, just store `ResourceAllocator` itself in an
`Arc<Mutex<>>`.

Apart from that, we get rid of the `ResourceAllocatorState` state
object, and just clone `ResourceAllocator` itself when we want to
save/restore.

Also, make the creation of `ResourceAllocato` infallible, since we know
that the ranges we are using are correct.

Finally, fix saving/restoring the state of ResourceAllocator. We were
actually not resetting it correctly upon snapshot restore. The reason
why this was not a problem is that we don't actually need to perform any
new allocations post restore at the moment. However, like this we are
ready when we need to perform any hot-plugging operations. Also, add a
unit-test to ensure that this logic works correctly.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

We were confusing queue indexex with event indexes, when passing the
index of the queue that needed to be triggered after handling events.

Fix the logic to pass the correct index. This refactors a bit the code
to signal the queues in each event handler method. With MMIO we don't
need to signal each queue independently (one signal will cause the guest
to scan all queues). With PCI though, we are using MSI-X, so we need to
signal each queue independently.

Also, change vsock functional integration tests to also run for
PCI-enabled microVMs.

Signed-off-by: Babis Chalios <bchalios@amazon.es>