kvm: kvm_init_vcpu take Error pointer

Clean up the error handling in kvm_init_vcpu so we can see what went
wrong more easily.

Make it take an Error ** and fill it out with what failed, including
the cpu id, so you can tell if it only fails at a given ID.

Replace the remaining DPRINTF by a trace.

This turns a:
kvm_init_vcpu failed: Invalid argument

into:
kvm_init_vcpu: kvm_get_vcpu failed (256): Invalid argument

and with the trace you then get to see:

19049@1595520414.310107:kvm_init_vcpu index: 169 id: 212
19050@1595520414.310635:kvm_init_vcpu index: 170 id: 256
qemu-system-x86_64: kvm_init_vcpu: kvm_get_vcpu failed (256): Invalid argument

which makes stuff a lot more obvious.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200723160915.129069-1-dgilbert@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

accel/kvm/kvm-all.c

@@ -441,17 +441,18 @@ static int kvm_get_vcpu(KVMState *s, unsigned long vcpu_id)
     return kvm_vm_ioctl(s, KVM_CREATE_VCPU, (void *)vcpu_id);
 }
 
-int kvm_init_vcpu(CPUState *cpu)
+int kvm_init_vcpu(CPUState *cpu, Error **errp)
 {
     KVMState *s = kvm_state;
     long mmap_size;
     int ret;
 
-    DPRINTF("kvm_init_vcpu\n");
+    trace_kvm_init_vcpu(cpu->cpu_index, kvm_arch_vcpu_id(cpu));
 
     ret = kvm_get_vcpu(s, kvm_arch_vcpu_id(cpu));
     if (ret < 0) {
-        DPRINTF("kvm_create_vcpu failed\n");
+        error_setg_errno(errp, -ret, "kvm_init_vcpu: kvm_get_vcpu failed (%lu)",
+                         kvm_arch_vcpu_id(cpu));
         goto err;
     }
 
@@ -462,7 +463,8 @@ int kvm_init_vcpu(CPUState *cpu)
     mmap_size = kvm_ioctl(s, KVM_GET_VCPU_MMAP_SIZE, 0);
     if (mmap_size < 0) {
         ret = mmap_size;
-        DPRINTF("KVM_GET_VCPU_MMAP_SIZE failed\n");
+        error_setg_errno(errp, -mmap_size,
+                         "kvm_init_vcpu: KVM_GET_VCPU_MMAP_SIZE failed");
         goto err;
     }
 
@@ -470,7 +472,9 @@ int kvm_init_vcpu(CPUState *cpu)
                         cpu->kvm_fd, 0);
     if (cpu->kvm_run == MAP_FAILED) {
         ret = -errno;
-        DPRINTF("mmap'ing vcpu state failed\n");
+        error_setg_errno(errp, ret,
+                         "kvm_init_vcpu: mmap'ing vcpu state failed (%lu)",
+                         kvm_arch_vcpu_id(cpu));
         goto err;
     }
 
@@ -480,6 +484,11 @@ int kvm_init_vcpu(CPUState *cpu)
     }
 
     ret = kvm_arch_init_vcpu(cpu);
+    if (ret < 0) {
+        error_setg_errno(errp, -ret,
+                         "kvm_init_vcpu: kvm_arch_init_vcpu failed (%lu)",
+                         kvm_arch_vcpu_id(cpu));
+    }
 err:
     return ret;
 }

accel/kvm/kvm-cpus.c

@@ -20,6 +20,7 @@
 #include "sysemu/runstate.h"
 #include "sysemu/cpus.h"
 #include "qemu/guest-random.h"
+#include "qapi/error.h"
 
 #include "kvm-cpus.h"
 
@@ -36,12 +37,7 @@ static void *kvm_vcpu_thread_fn(void *arg)
     cpu->can_do_io = 1;
     current_cpu = cpu;
 
-    r = kvm_init_vcpu(cpu);
-    if (r < 0) {
-        error_report("kvm_init_vcpu failed: %s", strerror(-r));
-        exit(1);
-    }
-
+    r = kvm_init_vcpu(cpu, &error_fatal);
     kvm_init_cpu_signals(cpu);
 
     /* signal CPU creation */

accel/kvm/kvm-cpus.h

@@ -14,7 +14,7 @@
 
 extern const CpusAccel kvm_cpus;
 
-int kvm_init_vcpu(CPUState *cpu);
+int kvm_init_vcpu(CPUState *cpu, Error **errp);
 int kvm_cpu_exec(CPUState *cpu);
 void kvm_destroy_vcpu(CPUState *cpu);
 void kvm_cpu_synchronize_post_reset(CPUState *cpu);

accel/kvm/trace-events

@@ -8,6 +8,7 @@ kvm_run_exit(int cpu_index, uint32_t reason) "cpu_index %d, reason %d"
 kvm_device_ioctl(int fd, int type, void *arg) "dev fd %d, type 0x%x, arg %p"
 kvm_failed_reg_get(uint64_t id, const char *msg) "Warning: Unable to retrieve ONEREG %" PRIu64 " from KVM: %s"
 kvm_failed_reg_set(uint64_t id, const char *msg) "Warning: Unable to set ONEREG %" PRIu64 " to KVM: %s"
+kvm_init_vcpu(int cpu_index, unsigned long arch_cpu_id) "index: %d id: %lu"
 kvm_irqchip_commit_routes(void) ""
 kvm_irqchip_add_msi_route(char *name, int vector, int virq) "dev %s vector %d virq %d"
 kvm_irqchip_update_msi_route(int virq) "Updating MSI route virq=%d"