Hyper-V driver has advertised support for multi-MSI, but any attempt at using the feature would fallback to a single MSI (non-starter for devices that require multi-MSI). The fallback also covered up other bugs related to multi-MSI functionality rooted in the driver not being able to tell MSIs apart.
These patches fix those bugs by enabling hv multi-MSI through IOMMU remapping, distinguishing multi-MSIs from the initial MSI of the MSI block, preventing retargeting of MSI subsets from invalidating the IRTE block, and aiding hypervisor to preserve the block of requests.
Tested on 4.19.252
Jeffrey Hugo (4): PCI: hv: Fix multi-MSI to allow more than one MSI vector PCI: hv: Fix hv_arch_irq_unmask() for multi-MSI PCI: hv: Reuse existing IRTE allocation in compose_msi_msg() PCI: hv: Fix interrupt mapping for multi-MSI
drivers/pci/controller/pci-hyperv.c | 99 +++++++++++++++++++++-------- 1 file changed, 73 insertions(+), 26 deletions(-)