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DRAFT: Add support for virtio-pci transport #5240

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@bchalios bchalios commented Jun 2, 2025

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  • I have read and understand CONTRIBUTING.md.
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  • I have described what is done in these changes, why they are needed, and
    how they are solving the problem in a clear and encompassing way.
  • I have updated any relevant documentation (both in code and in the docs)
    in the PR.
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    Runbook for Firecracker API changes.
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    integration tests.
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  • This functionality cannot be added in rust-vmm.

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codecov bot commented Jun 2, 2025

Codecov Report

Attention: Patch coverage is 24.23963% with 1644 lines in your changes missing coverage. Please review.

Project coverage is 75.58%. Comparing base (ca4f1e7) to head (c241ed1).

Files with missing lines Patch % Lines
src/vmm/src/devices/virtio/transport/pci/device.rs 0.00% 735 Missing ⚠️
src/vmm/src/device_manager/pci_mngr.rs 9.04% 382 Missing ⚠️
src/vmm/src/vstate/vm.rs 11.91% 244 Missing ⚠️
.../src/devices/virtio/transport/pci/common_config.rs 40.32% 111 Missing ⚠️
src/vmm/src/device_manager/mod.rs 60.93% 75 Missing ⚠️
src/vmm/src/builder.rs 75.00% 33 Missing ⚠️
src/vmm/src/vstate/resources.rs 52.77% 17 Missing ⚠️
src/vmm/src/devices/virtio/balloon/persist.rs 8.33% 11 Missing ⚠️
src/vmm/src/devices/virtio/queue.rs 8.33% 11 Missing ⚠️
src/pci/src/msix.rs 0.00% 10 Missing ⚠️
... and 6 more

❌ Your project check has failed because the head coverage (75.58%) is below the target coverage (80.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files
@@               Coverage Diff                @@
##           feature/pcie    #5240      +/-   ##
================================================
- Coverage         79.23%   75.58%   -3.66%     
================================================
  Files               262      265       +3     
  Lines             29347    30970    +1623     
================================================
+ Hits              23254    23408     +154     
- Misses             6093     7562    +1469     
Flag Coverage Δ
5.10-c5n.metal 75.01% <22.62%> (-4.04%) ⬇️
5.10-m5n.metal 75.01% <22.62%> (-4.04%) ⬇️
5.10-m6a.metal 74.03% <22.62%> (-4.14%) ⬇️
5.10-m6g.metal 71.21% <22.23%> (-3.97%) ⬇️
5.10-m6i.metal 75.01% <22.62%> (-4.03%) ⬇️
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5.10-m7g.metal 71.21% <22.23%> (-3.97%) ⬇️
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6.1-m6g.metal 71.21% <22.23%> (-3.97%) ⬇️
6.1-m6i.metal 75.05% <22.62%> (-4.04%) ⬇️
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@bchalios bchalios force-pushed the virtio-pci branch 7 times, most recently from a80faa9 to 15ed3eb Compare June 4, 2025 13:49
@bchalios bchalios force-pushed the virtio-pci branch 6 times, most recently from 61c6be1 to 9d18f11 Compare June 11, 2025 11:25
@bchalios bchalios force-pushed the virtio-pci branch 4 times, most recently from c56a8f7 to 93643a3 Compare June 16, 2025 10:34
bchalios added 11 commits June 16, 2025 13:16
We need the new KvmIrqRouting FamStruct wrapper from kvm-bindings, which
though forces us to update vmm-sys-util to 0.14.0 and also bump all
downstream dependencies of vmm-sys-util to use that version.

Signed-off-by: Babis Chalios <[email protected]>
Define thiserror::Error and displaydoc::Display for various error types
in the vended PCI crate. This way we can embed them in our error types
downstream. Also export a few types and struct fields that were private
and we will be needing them.

Signed-off-by: Babis Chalios <[email protected]>
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 <[email protected]>
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 <[email protected]>
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 <[email protected]>
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 <[email protected]>
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 <[email protected]>
Add a VirtIO PCI transport implementation. Nothing uses it at the
moment. This requires a few changes in our vended pci and vm-device
crates.

Signed-off-by: Babis Chalios <[email protected]>
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 <[email protected]>
Signed-off-by: Babis Chalios <[email protected]>
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 <[email protected]>
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 <[email protected]>
bchalios added 10 commits June 16, 2025 13:16
Remove the flags in FADT that were declaring we do not support MSI and
PCI ASPM.

Signed-off-by: Babis Chalios <[email protected]>
Create VirtIO devices using the PCI transport layer when user launched
microVM with --enable-pci.

Signed-off-by: Babis Chalios <[email protected]>
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 <[email protected]>
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 <[email protected]>
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 <[email protected]>
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 <[email protected]>
Support serializing the device-specific and transport state of a VirtIO
device that uses the PCI transport.

Signed-off-by: Babis Chalios <[email protected]>
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 <[email protected]>
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.

Signed-off-by: Babis Chalios <[email protected]>
Implement PCI device relocation logic for Vm type. Up until now, we were
only implementing it in a dummy way.

Signed-off-by: Babis Chalios <[email protected]>
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