hw/xen: Add xen_evtchn device for event channel emulation

Include basic support for setting HVM_PARAM_CALLBACK_IRQ to the global
vector method HVM_PARAM_CALLBACK_TYPE_VECTOR, which is handled in-kernel
by raising the vector whenever the vCPU's vcpu_info->evtchn_upcall_pending
flag is set.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>

1 files changed, 15 insertions, 0 deletions

diff --git a/target/i386/kvm/xen-emu.c b/target/i386/kvm/xen-emu.c
index ce858ac63c..435c51f625 100644
--- a/target/i386/kvm/xen-emu.c
+++ b/target/i386/kvm/xen-emu.c
@@ -22,6 +22,7 @@
 #include "sysemu/runstate.h"
 
 #include "hw/i386/kvm/xen_overlay.h"
+#include "hw/i386/kvm/xen_evtchn.h"
 
 #include "hw/xen/interface/version.h"
 #include "hw/xen/interface/sched.h"
@@ -510,6 +511,10 @@ static bool handle_set_param(struct kvm_xen_exit *exit, X86CPU *cpu,
     }
 
     switch (hp.index) {
+    case HVM_PARAM_CALLBACK_IRQ:
+        err = xen_evtchn_set_callback_param(hp.value);
+        xen_set_long_mode(exit->u.hcall.longmode);
+        break;
     default:
         return false;
     }
@@ -719,6 +724,16 @@ int kvm_xen_soft_reset(void)
 
     trace_kvm_xen_soft_reset();
 
+    /*
+     * Zero is the reset/startup state for HVM_PARAM_CALLBACK_IRQ. Strictly,
+     * it maps to HVM_PARAM_CALLBACK_TYPE_GSI with GSI#0, but Xen refuses to
+     * to deliver to the timer interrupt and treats that as 'disabled'.
+     */
+    err = xen_evtchn_set_callback_param(0);
+    if (err) {
+        return err;
+    }
+
     CPU_FOREACH(cpu) {
         async_run_on_cpu(cpu, do_vcpu_soft_reset, RUN_ON_CPU_NULL);
     }