Re: [Qemu-devel] s390: Fix cpu shutdown for KVM

[Christian Borntraeger <borntraeger@de.ibm.com>]

Something like the following? 

s390: Fix cpu shutdown for KVM

On s390 a shutdown is the state of all CPUs being either stopped
or disabled (for interrupts) waiting. We have to track this number
to call the shutdown sequence accordingly. This patch implements
the counting and shutdown handling for the kvm path in qemu.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
---
 hw/s390-virtio.c   |   21 +++++++++++++++++++++
 target-s390x/cpu.h |   12 ++++++++++++
 target-s390x/kvm.c |   21 +++++++++++++++++----
 3 files changed, 50 insertions(+), 4 deletions(-)

Index: b/hw/s390-virtio.c
===================================================================
--- a/hw/s390-virtio.c
+++ b/hw/s390-virtio.c
@@ -130,6 +130,26 @@ int s390_virtio_hypercall(CPUState *env,
     return r;
 }
 
+/*
+ * The number of running CPUs. On s390 a shutdown is the state of all CPUs
+ * being either stopped or disabled (for interrupts) waiting. We have to
+ * track this number to call the shutdown sequence accordingly. This
+ * number is modified either on startup or while holding the big qemu lock.
+ */
+static unsigned s390_running_cpus;
+
+void kvm_s390_add_running_cpu(CPUState *env)
+{
+    assert(env->halted == 0);
+    s390_running_cpus++;
+}
+
+unsigned kvm_s390_del_running_cpu(CPUState *env)
+{
+    assert(s390_running_cpus >= 1);
+    return --s390_running_cpus;
+}
+
 /* PC hardware initialisation */
 static void s390_init(ram_addr_t my_ram_size,
                       const char *boot_device,
@@ -189,6 +209,7 @@ static void s390_init(ram_addr_t my_ram_
 
     env->halted = 0;
     env->exception_index = 0;
+    kvm_s390_add_running_cpu(env);
 
     if (kernel_filename) {
         kernel_size = load_image(kernel_filename, qemu_get_ram_ptr(0));
Index: b/target-s390x/cpu.h
===================================================================
--- a/target-s390x/cpu.h
+++ b/target-s390x/cpu.h
@@ -292,6 +292,8 @@ void kvm_s390_interrupt(CPUState *env, i
 void kvm_s390_virtio_irq(CPUState *env, int config_change, uint64_t token);
 void kvm_s390_interrupt_internal(CPUState *env, int type, uint32_t parm,
                                  uint64_t parm64, int vm);
+void kvm_s390_add_running_cpu(CPUState *env);
+unsigned kvm_s390_del_running_cpu(CPUState *env);
 #else
 static inline void kvm_s390_interrupt(CPUState *env, int type, uint32_t code)
 {
@@ -307,6 +309,16 @@ static inline void kvm_s390_interrupt_in
                                                int vm)
 {
 }
+
+static inline void kvm_s390_add_running_cpu(CPUState *env)
+{
+}
+
+static inline unsigned kvm_s390_del_running_cpu(CPUState *env)
+{
+    return 0;
+}
+
 #endif
 CPUState *s390_cpu_addr2state(uint16_t cpu_addr);
 
Index: b/target-s390x/kvm.c
===================================================================
--- a/target-s390x/kvm.c
+++ b/target-s390x/kvm.c
@@ -185,6 +185,12 @@ void kvm_s390_interrupt_internal(CPUStat
         return;
     }
 
+    /*
+     * We can only deliver interrupts to (interrupt) enabled CPUs.
+     * We dont call kvm_s390_add_running_cpu here, since CPUs in enabled wait
+     * will wait inside the kernel (no exit). Therefore, the targeted
+     * CPUs was neither disabled waiting or stopped for qemu.
+     */
     env->halted = 0;
     env->exception_index = -1;
     qemu_cpu_kick(env);
@@ -301,6 +307,7 @@ static int s390_cpu_restart(CPUState *en
     kvm_s390_interrupt(env, KVM_S390_RESTART, 0);
     env->halted = 0;
     env->exception_index = -1;
+    kvm_s390_add_running_cpu(env);
     qemu_cpu_kick(env);
     dprintf("DONE: SIGP cpu restart: %p\n", env);
     return 0;
@@ -425,16 +432,24 @@ static int handle_intercept(CPUState *en
             r = handle_instruction(env, run);
             break;
         case ICPT_WAITPSW:
-            /* XXX What to do on system shutdown? */
+            if (kvm_s390_del_running_cpu(env) == 0) {
+                qemu_system_shutdown_request();
+            }
             env->halted = 1;
             env->exception_index = EXCP_HLT;
+            r = EXCP_HALTED;
             break;
         case ICPT_SOFT_INTERCEPT:
             fprintf(stderr, "KVM unimplemented icpt SOFT\n");
             exit(1);
             break;
         case ICPT_CPU_STOP:
-            qemu_system_shutdown_request();
+            if (kvm_s390_del_running_cpu(env) == 0) {
+                qemu_system_shutdown_request();
+            }
+            env->halted = 1;
+            env->exception_index = EXCP_HLT;
+            r = EXCP_HALTED;
             break;
         case ICPT_IO:
             fprintf(stderr, "KVM unimplemented icpt IO\n");
@@ -468,8 +483,6 @@ int kvm_arch_handle_exit(CPUState *env, 
 
     if (ret == 0) {
         ret = EXCP_INTERRUPT;
-    } else if (ret > 0) {
-        ret = 0;
     }
     return ret;
 }