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>
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>
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>
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>
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>
