bhyve emulates the guest PCI Command register so BAR sizing does not
disable physical decoding. However, PCIe Device Control was passed
through. A guest VFIO reset therefore performed a physical FLR, which
cleared physical Command, while the guest restored only its emulated
copy. The device remained assigned with bus mastering disabled and
could not fetch DMA descriptors.
Intercept guest FLR writes and issue a PPT-managed reset. Stop all
vCPUs, verify ownership, quiesce the function, perform only an FLR, and
restore the host-owned PCI configuration, decode, and bus-master state.
Keep the IOMMU domain in place. bhyve removes guest BAR mappings before
this ioctl; a later guest MEMEN write recreates them. Never escalate a
guest FLR to a power reset.
Reset the guest-owned Command, MSI, MSI-X, MSI-X table, INTx, and MRRS
state. PCIe 6.2 section 6.6.2 explicitly preserves MPS across FLR.
Virtualize MPS, MRRS, and Completion Timeout. Keep physical MPS and
completion-timeout policy host-owned, and apply physical MRRS with MPS
as its floor. Keep Phantom Functions Enable host-owned because it
changes requester identities visible to the IOMMU.
Serialize guest configuration transactions per function and gate
trapped and direct BAR access across the reset. Handle byte, word,
dword, and overlapping Device Control accesses.
A guest FLR can sleep for at least 100 ms. Reserve the target function
while dropping the global PPT lock so a guest cannot delay PPT lifecycle
operations for other VMs. Operations on the target wait for its reset
while other functions and VMs can proceed.
Check pcie_flr_supported() before destructive preparation so PPT applies
the generic PCI quirk policy. This includes VFs such as the 82599 which
implement FLR without advertising it.
Validated with two E610 VFs in a Linux 7.0 guest using VFIO no-IOMMU and
DPDK testpmd with two queues per VF. Byte, word, dword, and overlapping
FLR writes, 32 alternating resets, DPDK traffic, and ixgbevf
reattachment all completed while the sibling VF and host PCIe remained
healthy. This fixes Linux VFIO no-IOMMU with DPDK PMDs.
Reviewed by: markj
MFC after: 2 weeks
Sponsored by: BBOX.io
Kevin Bowling
c8343ba84a