Avi Kivity wrote: > Xu, Anthony wrote: >> Xiantao and I have found the root cause, >> Qemu emulates PIIX chipset, all pci devices can only use irq 10.11, >> which is confiured inside chipset interrupt routing table. Even >> though IOAPIC have 24 interrupt pins. >> While KVM/IA64 use the same Guest Firmware with what XEN/IA64 which >> use different "interrupt routing algorithm". >> Means the pci device irq doesn't match between qemu and Guest >> Firmware in KVM/IA64. So guest didn't get pci device interrupt. >> >> Obviously there are two ways to fix it. >> 1. modify qemu side, all pci devices use irq larger than or equal to >> 16, we need to come out an algorithm to calculate irq from pci >> device(bus number,device number, function number), >> then we also need to modify IA32 Guest BIOS to present the same >> pci device irq (use same algorithm) to guest OS. Avi seems not want >> to modify qemu a lot. >> >> 2. modify IA64 guest firmware, two pros, (1)all pci devices use only >> 10,11 two irqs, so if there are many pci device, there are a lot of >> interrupt sharing, which impact performance negatively >> (2) We need to maintain two versions fo IA64 guest firmwares, one >> for KVM/IA64, the other for XEN/IA64, which is not what I want. >> >> >> What's your suggestion? >> >> > > Allowing qemu to use all ioapic interrupt pins will reduce interrupt > sharing on x86, which is a good thing, so I prefer the first option > too. Thanks for your support, I preper option #1, Any suggestion for the mapping from BDF to irq. In XEN both in IA64/IA32, BIOS provides a 48 pin IOAPIC ( usually it is 24) to reduce irq sharing. 0~15 are reserved for legacy devices. Pci devices use 16~47, The mapping is like ((bdf >> 3) *4) %(48-16) + 16 Means every pci interrup pin( irqA, irqB, irqC, irqD) of every pci device use different irq pin of IOAPIC if number of pci devices is less than 8. I think it can avoid interrupt sharing in most case. If use this method, we can share same IA64 guest BIOS between XEN/IA64 and KVM/IA64. What do you think? Thanks, Anthony -- To unsubscribe from this list: send the line "unsubscribe kvm-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
