virtio-snd: add WFI handling to VMMs

Signed-off-by: Alex Brown <[email protected]>

examples/virtio-snd/client_vmm.c

@@ -214,7 +214,8 @@ void notified(microkit_channel ch) {
  * the VMM to handle.
  */
 void fault(microkit_id id, microkit_msginfo msginfo) {
-    bool success = fault_handle(id, msginfo);
+    bool wfi = false;
+    bool success = fault_handle(id, msginfo, &wfi);
     if (success) {
         /* Now that we have handled the fault successfully, we reply to it so
          * that the guest can resume execution. */

examples/virtio-snd/snd_driver_vmm.c

@@ -57,6 +57,8 @@ uintptr_t guest_ram_vaddr;
 #define MAX_IRQ_CH 63
 int passthrough_irq_map[MAX_IRQ_CH];
 
+bool suspended;
+size_t suspend_pc;
 
 #define SERIAL_MUX_TX_CH 1
 #define SERIAL_MUX_RX_CH 2
@@ -204,13 +206,21 @@ void init(void) {
 #error Need to define passthrough IRQs
 #endif
 
+    suspended = false;
+    suspend_pc = 0;
     /* Finally start the guest */
     guest_start(GUEST_VCPU_ID, kernel_pc, GUEST_DTB_VADDR, GUEST_INIT_RAM_DISK_VADDR);
 }
 
 void notified(microkit_channel ch) {
     bool success;
 
+    if (suspended) {
+        LOG_VMM("waking\n");
+        microkit_vm_restart(GUEST_VCPU_ID, suspend_pc);
+        suspended = false;
+    }
+
     switch (ch) {
         case SERIAL_MUX_RX_CH: {
             /* We have received an event from the serial multiplexer, so we
@@ -243,8 +253,15 @@ void notified(microkit_channel ch) {
  * the VMM to handle.
  */
 void fault(microkit_id id, microkit_msginfo msginfo) {
-    bool success = fault_handle(id, msginfo);
+    bool wfi = false;
+    bool success = fault_handle(id, msginfo, &wfi);
     if (success) {
+        if (wfi) {
+            LOG_VMM("sleeping\n");
+            microkit_vm_stop(GUEST_VCPU_ID);
+            suspend_pc = microkit_mr_get(seL4_VMFault_IP);
+            suspended = true;
+        }
         /* Now that we have handled the fault successfully, we reply to it so
          * that the guest can resume execution. */
         microkit_fault_reply(microkit_msginfo_new(0, 0));