Direct Injection of MSIs into KVM guests on arm64

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One Line Summary

Discussion around direct injection of MSIs into KVM guests on arm64


This builds up on Will Deacon’s proposal related to MSIs in guests.

Another level of complexity in dealing with MSIs in guests is reached with direct injection into guests. The ARM GICv4 architecture allows for this feature to be implemented relatively easily at the HW level, but of course leaves it to us kernel hackers to come up with the plumbing.

Among the problems to be solved:
- How to express the mapping of physical devices to the guest’s view?
- Should we use the current VFIO model where the MSI-X tables are left untouched (creating potential ordering issues between programming the interrupt controller and the PCI device)?
- Or should we rely on the isolation properties that are offered by the hardware to allow for a slightly more liberal access?

This of course has wide-ranging userspace impacts for the KVM userspace (which is the major consumer for this).


kvm, PCI, VFIO, msi


  • Marc Zyngier

    ARM Ltd


    Co-maintainer for the KVM on arm/arm64, irqchips and irqdomains subsystems.