s390x: refactor reset/reipl handling

Calling pause_all_vcpus()/resume_all_vcpus() from a VCPU thread might
not be the best idea. As pause_all_vcpus() temporarily drops the qemu
mutex, two parallel calls to pause_all_vcpus() can be active at a time,
resulting in a deadlock. (either by two VCPUs or by the main thread and a
VCPU)

Let's handle it via the main loop instead, as suggested by Paolo. If we
would have two parallel reset requests by two different VCPUs at the
same time, the last one would win.

We use the existing ipl device to handle it. The nice side effect is
that we can get rid of reipl_requested.

This change implies that all reset handling now goes via the common
path, so "no-reboot" handling is now active for all kinds of reboots.

Let's execute any CPU initialization code on the target CPU using
run_on_cpu.

Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20180424101859.10239-1-david@redhat.com>
Acked-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>

1 files changed, 38 insertions, 5 deletions

diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c
index 150f6c0..04245b5 100644
--- a/hw/s390x/ipl.c
+++ b/hw/s390x/ipl.c
@@ -26,6 +26,7 @@
 #include "qemu/config-file.h"
 #include "qemu/cutils.h"
 #include "qemu/option.h"
+#include "exec/exec-all.h"
 
 #define KERN_IMAGE_START                0x010000UL
 #define KERN_PARM_AREA                  0x010480UL
@@ -488,12 +489,20 @@ IplParameterBlock *s390_ipl_get_iplb(void)
     return &ipl->iplb;
 }
 
-void s390_reipl_request(void)
+void s390_ipl_reset_request(CPUState *cs, enum s390_reset reset_type)
 {
     S390IPLState *ipl = get_ipl_device();
 
-    ipl->reipl_requested = true;
-    if (ipl->iplb_valid &&
+    if (reset_type == S390_RESET_EXTERNAL || reset_type == S390_RESET_REIPL) {
+        /* use CPU 0 for full resets */
+        ipl->reset_cpu_index = 0;
+    } else {
+        ipl->reset_cpu_index = cs->cpu_index;
+    }
+    ipl->reset_type = reset_type;
+
+    if (reset_type == S390_RESET_REIPL &&
+        ipl->iplb_valid &&
         !ipl->netboot &&
         ipl->iplb.pbt == S390_IPL_TYPE_CCW &&
         is_virtio_scsi_device(&ipl->iplb)) {
@@ -510,6 +519,31 @@ void s390_reipl_request(void)
         }
     }
     qemu_system_reset_request(SHUTDOWN_CAUSE_GUEST_RESET);
+    /* as this is triggered by a CPU, make sure to exit the loop */
+    if (tcg_enabled()) {
+        cpu_loop_exit(cs);
+    }
+}
+
+void s390_ipl_get_reset_request(CPUState **cs, enum s390_reset *reset_type)
+{
+    S390IPLState *ipl = get_ipl_device();
+
+    *cs = qemu_get_cpu(ipl->reset_cpu_index);
+    if (!*cs) {
+        /* use any CPU */
+        *cs = first_cpu;
+    }
+    *reset_type = ipl->reset_type;
+}
+
+void s390_ipl_clear_reset_request(void)
+{
+    S390IPLState *ipl = get_ipl_device();
+
+    ipl->reset_type = S390_RESET_EXTERNAL;
+    /* use CPU 0 for full resets */
+    ipl->reset_cpu_index = 0;
 }
 
 static void s390_ipl_prepare_qipl(S390CPU *cpu)
@@ -556,11 +590,10 @@ static void s390_ipl_reset(DeviceState *dev)
 {
     S390IPLState *ipl = S390_IPL(dev);
 
-    if (!ipl->reipl_requested) {
+    if (ipl->reset_type != S390_RESET_REIPL) {
         ipl->iplb_valid = false;
         memset(&ipl->iplb, 0, sizeof(IplParameterBlock));
     }
-    ipl->reipl_requested = false;
 }
 
 static void s390_ipl_class_init(ObjectClass *klass, void *data)