[Qemu-devel] [PATCH v2 0/2] spapr: reduce the number of IRQ

[Cédric Le Goater]

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