Hello,
When QEMU switches to the XIVE interrupt mode, it creates all the guest interrupts at the level of the KVM device. These interrupts are backed by real HW interrupts from the IPI interrupt pool of the XIVE controller. Currently, this is done from the QEMU main thread, which results in allocating all interrupts from the chip on which QEMU is running. IPIs are not distributed across the system and the load is not well balanced across the interrupt controllers. Change the vCPU IPI allocation to run from the vCPU context. The associated XIVE IPI interrupt will be allocated on the chip on which the vCPU is running and improve distribution of the IPIs in the system. When the vCPUs are pinned, this will make the IPI local to the chip of the vCPU. It will reduce rerouting between interrupt controllers and gives better performance. I did some basic migration testing with the 'dual' and 'xive' modes, also tried CPU hoplug. I haven't tried migration with older pseries machine. Thanks, C. Cédric Le Goater (4): spapr/xive: Modify kvm_cpu_is_enabled() interface spapr/xive: Use kvmppc_xive_source_reset() in post_load spapr/xive: Allocate IPIs independently from the other sources spapr/xive: Allocate vCPU IPIs from the vCPU contexts hw/intc/spapr_xive_kvm.c | 102 ++++++++++++++++++++++++++++++++------- 1 file changed, 84 insertions(+), 18 deletions(-) -- 2.25.4