Re: [qemu-s390x] [PATCH v1] s390x: refactor reset/reipl handling

[Christian Borntraeger]

On 04/24/2018 12:18 PM, David Hildenbrand wrote:
> 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.

Ok, this breaks the s390 IPL process when -no-reboot  is specified.
The bios does a diagnose 308 subcode 1 to jump to the final image while
at the same time resetting all devices. This is now blocked with -no-reboot
(although it is actually the boot)


I have noticed that with virt-install on iso images since virt-install
specifies -no-reboot.

Something like this seems to help but it is not a nice solution.

diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c
index 0d67349004..7b32698eaa 100644
--- a/hw/s390x/ipl.c
+++ b/hw/s390x/ipl.c
@@ -534,8 +534,14 @@ void s390_ipl_reset_request(CPUState *cs, enum s390_reset 
reset_type)
              */
             ipl->iplb_valid = s390_gen_initial_iplb(ipl);
         }
+        qemu_system_reset_request(SHUTDOWN_CAUSE_GUEST_RESET);
+    } else  if (reset_type == S390_RESET_MODIFIED_CLEAR ||
+                reset_type == S390_RESET_LOAD_NORMAL) {
+       /* ignore -no-reboot */
+        qemu_system_reset_request(SHUTDOWN_CAUSE_GUEST_RESET_FORCE);
+    } else {
+        qemu_system_reset_request(SHUTDOWN_CAUSE_GUEST_RESET);
     }
-    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);
diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
index e893f72f3b..e9b11fd6cb 100644
--- a/include/sysemu/sysemu.h
+++ b/include/sysemu/sysemu.h
@@ -44,6 +44,9 @@ typedef enum ShutdownCause {
                                      turns that into a shutdown */
     SHUTDOWN_CAUSE_GUEST_PANIC,   /* Guest panicked, and command line turns
                                      that into a shutdown */
+    SHUTDOWN_CAUSE_GUEST_RESET_FORCE,/* Guest reset that should ignore 
--no-reboot
+                                     useful for the subsystem resets on s390 
done
+                                     for kdump and kexec */
     SHUTDOWN_CAUSE__MAX,
 } ShutdownCause;
 
diff --git a/vl.c b/vl.c
index b3426e03d0..18f379e833 100644
--- a/vl.c
+++ b/vl.c
@@ -1674,7 +1674,9 @@ void qemu_system_guest_panicked(GuestPanicInformation 
*info)
 
 void qemu_system_reset_request(ShutdownCause reason)
 {
-    if (no_reboot) {
+    if (reason == SHUTDOWN_CAUSE_GUEST_RESET_FORCE) {
+           reset_requested = SHUTDOWN_CAUSE_GUEST_RESET;
+    } else if (no_reboot) {
         shutdown_requested = reason;
     } else {
         reset_requested = reason;
-- 
2.17.0