minor changes to yields to avoid guest lock ups due to irq flooding scenarios

diff --git a/palacios/src/palacios/svm.c b/palacios/src/palacios/svm.c
index 5fadae1..d2444ac 100644 (file)
--- a/palacios/src/palacios/svm.c
+++ b/palacios/src/palacios/svm.c
@@ -293,7 +293,6 @@ static int start_svm_guest(struct guest_info *info) {
        */
 
        // disable global interrupts for vm state transition
-
        v3_clgi();
 
 
@@ -311,6 +310,11 @@ static int start_svm_guest(struct guest_info *info) {
        // reenable global interrupts after vm exit
        v3_stgi();
 
+
+       // Conditionally yield the CPU if the timeslice has expired
+       v3_yield_cond(info);
+
+
        v3_update_time(info, tmp_tsc - info->time_state.cached_host_tsc);
        num_exits++;
        
@@ -322,10 +326,6 @@ static int start_svm_guest(struct guest_info *info) {
            }
        }
 
-     
-       // Conditionally yield the CPU if the timeslice has expired
-       v3_yield_cond(info);
-
        if (v3_handle_svm_exit(info) != 0) {
            vmcb_ctrl_t * guest_ctrl = GET_VMCB_CTRL_AREA((vmcb_t*)(info->vmm_data));
            addr_t host_addr;

diff --git a/palacios/src/palacios/svm_halt.c b/palacios/src/palacios/svm_halt.c
index 16239e8..2e6f9e2 100644 (file)
--- a/palacios/src/palacios/svm_halt.c
+++ b/palacios/src/palacios/svm_halt.c
@@ -30,7 +30,7 @@
 
 
 //
-// This should trigger a #GP if cpl!=0, otherwise, yield to host
+// This should trigger a #GP if cpl != 0, otherwise, yield to host
 //
 
 int v3_handle_svm_halt(struct guest_info * info) {
@@ -39,8 +39,8 @@ int v3_handle_svm_halt(struct guest_info * info) {
        v3_raise_exception(info, GPF_EXCEPTION);
     } else {
     
-       ullong_t yield_start = 0;
-       ullong_t yield_stop = 0;
+       uint64_t yield_start = 0;
+       uint64_t yield_stop = 0;
        uint32_t gap = 0;
        
        PrintDebug("CPU Yield\n");
@@ -53,7 +53,18 @@ int v3_handle_svm_halt(struct guest_info * info) {
        //v3_update_time(info, yield_stop - yield_start);
        gap = yield_stop - yield_start;
 
-       v3_raise_irq(info, 0);
+       /*  WARNING!!! WARNING!!!
+        *  
+        * DO NOT REMOVE THIS CONDITIONAL!!!
+        *
+        * It is common for an OS to issue an IO op, and then sit in a halt loop
+        * waiting for the device to complete and raise an irq.
+        * If you remove this then the timer interrupt will ALWAYS subvert the completion 
+        * interrupt and stall the guest.
+        */
+       if (!v3_intr_pending(info)) {
+           v3_raise_irq(info, 0);
+       }
 
        
        PrintDebug("CPU Yield Done (%d cycles)\n", gap);