xics-kvm: Support for in-kernel XICS interrupt controller

Recent (host) kernels support emulating the PAPR defined "XICS" interrupt
controller system within KVM.  This patch allows qemu to initialize and
configure the in-kernel XICS, and keep its state in sync with qemu's XICS
state as necessary.

This should give considerable performance improvements.  e.g. on a simple
IPI ping-pong test between hardware threads, using qemu XICS gives us
around 5,000 irqs/second, whereas the in-kernel XICS gives us around
70,000 irqs/s on the same hardware configuration.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
[Mike Qiu <qiudayu@linux.vnet.ibm.com>: fixed mistype which caused ics_set_kvm_state() to fail]
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Alexander Graf <agraf@suse.de>

1 files changed, 20 insertions, 1 deletions

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index f65dadc356..c0613e467c 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -168,7 +168,26 @@ static XICSState *xics_system_init(int nr_servers, int nr_irqs)
 {
     XICSState *icp = NULL;
 
-    icp = try_create_xics(TYPE_XICS, nr_servers, nr_irqs);
+    if (kvm_enabled()) {
+        QemuOpts *machine_opts = qemu_get_machine_opts();
+        bool irqchip_allowed = qemu_opt_get_bool(machine_opts,
+                                                "kernel_irqchip", true);
+        bool irqchip_required = qemu_opt_get_bool(machine_opts,
+                                                  "kernel_irqchip", false);
+        if (irqchip_allowed) {
+            icp = try_create_xics(TYPE_KVM_XICS, nr_servers, nr_irqs);
+        }
+
+        if (irqchip_required && !icp) {
+            perror("Failed to create in-kernel XICS\n");
+            abort();
+        }
+    }
+
+    if (!icp) {
+        icp = try_create_xics(TYPE_XICS, nr_servers, nr_irqs);
+    }
+
     if (!icp) {
         perror("Failed to create XICS\n");
         abort();