spapr/irq: Only claim VALID interrupts at the KVM level

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.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20190911133937.2716-3-clg@kaod.org>
Signed-off-by: Greg Kurz <groug@kaod.org>
Message-Id: <156942766014.1274533.10792048853177121231.stgit@bahia.lan>
[dwg: Folded in fix up from Greg Kurz]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

1 files changed, 8 insertions, 0 deletions

diff --git a/hw/intc/xics_kvm.c b/hw/intc/xics_kvm.c
index a4d2e876cc..ba90d6dc96 100644
--- a/hw/intc/xics_kvm.c
+++ b/hw/intc/xics_kvm.c
@@ -190,6 +190,10 @@ void ics_get_kvm_state(ICSState *ics)
     for (i = 0; i < ics->nr_irqs; i++) {
         ICSIRQState *irq = &ics->irqs[i];
 
+        if (ics_irq_free(ics, i)) {
+            continue;
+        }
+
         kvm_device_access(kernel_xics_fd, KVM_DEV_XICS_GRP_SOURCES,
                           i + ics->offset, &state, false, &error_fatal);
 
@@ -301,6 +305,10 @@ int ics_set_kvm_state(ICSState *ics, Error **errp)
         Error *local_err = NULL;
         int ret;
 
+        if (ics_irq_free(ics, i)) {
+            continue;
+        }
+
         ret = ics_set_kvm_state_one(ics, i, &local_err);
         if (ret < 0) {
             error_propagate(errp, local_err);