Hello, A typical pseries VM with 16 vCPUs, one disk, one network adapater uses less than 100 interrupts but the whole IRQ number space of the QEMU machine is allocated at reset time and it is 8K wide. This is wasting a considerable amount of interrupt numbers in the global IRQ space which has 1M interrupts per socket on a POWER9.
To optimise the HW resources, only request at the KVM level interrupts which have been claimed by the guest. This will help to increase the maximum number of VMs per system and also help supporting nested guests using the XIVE interrupt mode. Thanks, C. Changes since v1: - split the patch - removed useless 'reset_all' machine flag which supposed to preserve migration compatibility Cédric Le Goater (2): spapr/irq: Introduce an ics_irq_free() helper spapr/irq: Only claim VALID interrupts at the KVM level include/hw/ppc/xics.h | 5 +++++ hw/intc/spapr_xive_kvm.c | 29 ++++++++++++++++++++++++++--- hw/intc/xics_kvm.c | 8 ++++++++ hw/ppc/spapr_irq.c | 9 +++------ 4 files changed, 42 insertions(+), 9 deletions(-) -- 2.21.0