Hi Xiang, On Tue, 12 Jul 2022 13:55:16 +0100, "chenxiang (M)" <chenxiang66@xxxxxxxxxxxxx> wrote: > > Hi, > I encounter a issue related to GICv4 enable on ARM64 platform (kernel > 5.19-rc4, qemu 6.2.0): > We have a accelaration module whose VF has 3 MSI interrupts, and we > passthrough it to virtual machine with following steps: > > echo 0000:79:00.1 > /sys/bus/pci/drivers/hisi_hpre/unbind > echo vfio-pci > > /sys/devices/pci0000\:78/0000\:78\:00.0/0000\:79\:00.1/driver_override > echo 0000:79:00.1 > /sys/bus/pci/drivers_probe > > Then we boot VM with "-device vfio-pci,host=79:00.1,id=net0 \". > When insmod the driver which registers 3 PCI MSI interrupts in VM, > some exception print occur as following: > > vfio-pci 0000:3a:00.1: irq bypass producer (token 000000008f08224d) > registration fails: 66311 > > I find that bit[6:4] of register PCI_MSI_FLAGS is 2 (4 MSI interrupts) > though we only register 3 PCI MSI interrupt, > > and only 3 MSI interrupt is activated at last. > It allocates 4 vectors in function vfio_msi_enable() (qemu) as it > reads the register PCI_MSI_FLAGS. > Later it will call system call VFIO_DEVICE_SET_IRQS to set forwarding > for those interrupts > using function kvm_vgic_v4_set_forrwarding() as GICv4 is enabled. For > interrupt 0~2, it success to set forwarding as they are already > activated, > but for the 4th interrupt, it is not activated, so ite is not found in > function vgic_its_resolve_lpi(), so above printk occurs. > > It seems that we only allocate and activate 3 MSI interrupts in guest > while it tried to set forwarding for 4 MSI interrupts in host. > Do you have any idea about this issue? I have a hunch: QEMU cannot know that the guest is only using 3 MSIs out of the 4 that the device can use, and PCI/Multi-MSI only has a single enable bit for all MSIs. So it probably iterates over all possible MSIs and enable the forwarding. Since the guest has only created 3 mappings in the virtual ITS, the last call fails. I would expect the guest to still work properly though. Thanks, M. -- Without deviation from the norm, progress is not possible.
