[Qemu-devel] [PATCH v3 0/3] kvm: report available guest crash parameters

[Qemu-devel] [PATCH v3 0/3] kvm: report available guest crash parameters

[Denis V. Lunev]

Windows reports BSOD parameters through Hyper-V crash MSRs. This
information is very useful for initial crash analysis and thus
it would be nice to see it in the QEMU log file. There is suitable
log mask for the purpose.

Linux guest does not provide this information, but still it would
be nice to log that we have crashed.

Changes from v3:
- existing kvm_cpu_synchronize_state() used to fetch HV crash MSRs
  (hence, no separate storage for these MSRs in struct X86CPU anymore)
- qapi_free_GuestPanicInformation() used to release memory

Changes from v2:
- fixed PPC compilation

Changes since v1:
- patches resplit
- created property to query crash parameters
- crash parameters added to panic event

Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Marcelo Tosatti <mtosatti@redhat.com>
CC: Richard Henderson <rth@twiddle.net>
CC: Eduardo Habkost <ehabkost@redhat.com>
CC: Eric Blake <eblake@redhat.com>
CC: Markus Armbruster <armbru@redhat.com>

Anton Nefedov (3):
  i386/cpu: add crash-information QOM property
  report guest crash information in GUEST_PANICKED event
  vl: log available guest crash information

 hw/misc/pvpanic.c       |  2 +-
 hw/ppc/spapr_rtas.c     |  3 ++-
 include/qom/cpu.h       | 10 +++++++++
 include/sysemu/kvm.h    |  2 ++
 include/sysemu/sysemu.h |  2 +-
 kvm-all.c               |  3 ++-
 qapi-schema.json        | 24 +++++++++++++++++++++
 qapi/event.json         |  6 ++++--
 qom/cpu.c               | 11 ++++++++++
 stubs/Makefile.objs     |  1 +
 stubs/kvm-crash.c       |  8 +++++++
 target/i386/cpu.c       | 55 +++++++++++++++++++++++++++++++++++++++++++++++++
 target/i386/cpu.h       |  3 +++
 target/i386/kvm.c       | 41 ++++++++++++++++++++++++++++++++++++
 target/s390x/kvm.c      |  4 ++--
 vl.c                    | 23 ++++++++++++++++++---
 16 files changed, 187 insertions(+), 11 deletions(-)
 create mode 100644 stubs/kvm-crash.c

-- 
2.7.4

[Qemu-devel] [PATCH v4 1/3] i386/cpu: add crash-information QOM property

[Denis V. Lunev]

From: Anton Nefedov <anton.nefedov@virtuozzo.com>

Windows reports BSOD parameters through Hyper-V crash MSRs. This
information is very useful for initial crash analysis and thus
it would be nice to have a way to fetch it.

Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
---
 kvm-all.c         |  1 +
 qapi-schema.json  | 24 ++++++++++++++++++++++++
 target/i386/cpu.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 75 insertions(+)

diff --git a/kvm-all.c b/kvm-all.c
index a27c880..64f46c8 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -2000,6 +2000,7 @@ int kvm_cpu_exec(CPUState *cpu)
                 ret = EXCP_INTERRUPT;
                 break;
             case KVM_SYSTEM_EVENT_CRASH:
+                kvm_cpu_synchronize_state(cpu);
                 qemu_mutex_lock_iothread();
                 qemu_system_guest_panicked();
                 qemu_mutex_unlock_iothread();
diff --git a/qapi-schema.json b/qapi-schema.json
index cbdffdd..9cb6ac5 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -5846,6 +5846,30 @@
   'data': [ 'pause', 'poweroff' ] }
 
 ##
+# @GuestPanicInformation:
+#
+# Information about a guest panic
+#
+# Since: 2.9
+##
+{'union': 'GuestPanicInformation',
+ 'data': { 'hyper-v': 'GuestPanicInformationHyperV' } }
+
+##
+# @GuestPanicInformationHyperV:
+#
+# Hyper-V specific guest panic information (HV crash MSRs)
+#
+# Since: 2.9
+##
+{'struct': 'GuestPanicInformationHyperV',
+ 'data': { 'arg1': 'uint64',
+           'arg2': 'uint64',
+           'arg3': 'uint64',
+           'arg4': 'uint64',
+           'arg5': 'uint64' } }
+
+##
 # @rtc-reset-reinjection:
 #
 # This command will reset the RTC interrupt reinjection backlog.
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index eb49980..71aa91f 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -3495,6 +3495,53 @@ static void x86_cpu_register_feature_bit_props(X86CPU *cpu,
     x86_cpu_register_bit_prop(cpu, name, &cpu->env.features[w], bitnr);
 }
 
+static GuestPanicInformation *x86_cpu_get_crash_info(CPUState *cs)
+{
+    X86CPU *cpu = X86_CPU(cs);
+    CPUX86State *env = &cpu->env;
+    GuestPanicInformation *panic_info = NULL;
+
+    if (env->features[FEAT_HYPERV_EDX] & HV_X64_GUEST_CRASH_MSR_AVAILABLE) {
+        GuestPanicInformationHyperV *panic_info_hv =
+            g_malloc0(sizeof(GuestPanicInformationHyperV));
+        panic_info = g_malloc0(sizeof(GuestPanicInformation));
+
+        panic_info->type = GUEST_PANIC_INFORMATION_KIND_HYPER_V;
+        panic_info->u.hyper_v.data = panic_info_hv;
+
+        assert(HV_X64_MSR_CRASH_PARAMS >= 5);
+        panic_info_hv->arg1 = env->msr_hv_crash_params[0];
+        panic_info_hv->arg2 = env->msr_hv_crash_params[1];
+        panic_info_hv->arg3 = env->msr_hv_crash_params[2];
+        panic_info_hv->arg4 = env->msr_hv_crash_params[3];
+        panic_info_hv->arg5 = env->msr_hv_crash_params[4];
+    }
+
+    return panic_info;
+}
+static void x86_cpu_get_crash_info_qom(Object *obj, Visitor *v,
+                                       const char *name, void *opaque,
+                                       Error **errp)
+{
+    CPUState *cs = CPU(obj);
+    GuestPanicInformation *panic_info;
+
+    if (!cs->crash_occurred) {
+        error_setg(errp, "No crash occured");
+        return;
+    }
+
+    panic_info = x86_cpu_get_crash_info(cs);
+    if (panic_info == NULL) {
+        error_setg(errp, "No crash information");
+        return;
+    }
+
+    visit_type_GuestPanicInformation(v, "crash-information", &panic_info,
+                                     errp);
+    qapi_free_GuestPanicInformation(panic_info);
+}
+
 static void x86_cpu_initfn(Object *obj)
 {
     CPUState *cs = CPU(obj);
@@ -3530,6 +3577,9 @@ static void x86_cpu_initfn(Object *obj)
                         x86_cpu_get_feature_words,
                         NULL, NULL, (void *)cpu->filtered_features, NULL);
 
+    object_property_add(obj, "crash-information", "GuestPanicInformation",
+                        x86_cpu_get_crash_info_qom, NULL, NULL, NULL, NULL);
+
     cpu->hyperv_spinlock_attempts = HYPERV_SPINLOCK_NEVER_RETRY;
 
     for (w = 0; w < FEATURE_WORDS; w++) {
-- 
2.7.4

[Qemu-devel] [PATCH v4 2/3] report guest crash information in GUEST_PANICKED event

[Denis V. Lunev]

From: Anton Nefedov <anton.nefedov@virtuozzo.com>

it's not very convenient to use the crash-information property interface,
so provide a CPU class callback to get the guest crash information, and pass
that information in the event

Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
---
 hw/misc/pvpanic.c       |  2 +-
 hw/ppc/spapr_rtas.c     |  3 ++-
 include/qom/cpu.h       | 10 ++++++++++
 include/sysemu/sysemu.h |  2 +-
 kvm-all.c               |  2 +-
 qapi/event.json         |  6 ++++--
 qom/cpu.c               | 11 +++++++++++
 target/i386/cpu.c       |  1 +
 target/s390x/kvm.c      |  4 ++--
 vl.c                    | 11 ++++++++---
 10 files changed, 41 insertions(+), 11 deletions(-)

diff --git a/hw/misc/pvpanic.c b/hw/misc/pvpanic.c
index 0ac1e6a..57da7f2 100644
--- a/hw/misc/pvpanic.c
+++ b/hw/misc/pvpanic.c
@@ -42,7 +42,7 @@ static void handle_event(int event)
     }
 
     if (event & PVPANIC_PANICKED) {
-        qemu_system_guest_panicked();
+        qemu_system_guest_panicked(NULL);
         return;
     }
 }
diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
index bb19944..619f32c 100644
--- a/hw/ppc/spapr_rtas.c
+++ b/hw/ppc/spapr_rtas.c
@@ -334,7 +334,8 @@ static void rtas_ibm_os_term(PowerPCCPU *cpu,
 {
     target_ulong ret = 0;
 
-    qapi_event_send_guest_panicked(GUEST_PANIC_ACTION_PAUSE, &error_abort);
+    qapi_event_send_guest_panicked(GUEST_PANIC_ACTION_PAUSE, false, NULL,
+                                   &error_abort);
 
     rtas_st(rets, 0, ret);
 }
diff --git a/include/qom/cpu.h b/include/qom/cpu.h
index ca4d0fb..f95a6c3 100644
--- a/include/qom/cpu.h
+++ b/include/qom/cpu.h
@@ -156,6 +156,7 @@ typedef struct CPUClass {
                            uint8_t *buf, int len, bool is_write);
     void (*dump_state)(CPUState *cpu, FILE *f, fprintf_function cpu_fprintf,
                        int flags);
+    GuestPanicInformation* (*get_crash_info)(CPUState *cpu);
     void (*dump_statistics)(CPUState *cpu, FILE *f,
                             fprintf_function cpu_fprintf, int flags);
     int64_t (*get_arch_id)(CPUState *cpu);
@@ -469,6 +470,15 @@ int cpu_write_elf32_qemunote(WriteCoreDumpFunction f, CPUState *cpu,
                              void *opaque);
 
 /**
+ * cpu_get_crash_info:
+ * @cpu: The CPU to get crash information for
+ *
+ * Gets the previously saved crash information.
+ * Caller is responsible for freeing the data.
+ */
+GuestPanicInformation *cpu_get_crash_info(CPUState *cpu);
+
+/**
  * CPUDumpFlags:
  * @CPU_DUMP_CODE:
  * @CPU_DUMP_FPU: dump FPU register state, not just integer
diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
index 4d50694..2c39bed 100644
--- a/include/sysemu/sysemu.h
+++ b/include/sysemu/sysemu.h
@@ -64,7 +64,7 @@ int qemu_shutdown_requested_get(void);
 int qemu_reset_requested_get(void);
 void qemu_system_killed(int signal, pid_t pid);
 void qemu_system_reset(bool report);
-void qemu_system_guest_panicked(void);
+void qemu_system_guest_panicked(GuestPanicInformation *info);
 size_t qemu_target_page_bits(void);
 
 void qemu_add_exit_notifier(Notifier *notify);
diff --git a/kvm-all.c b/kvm-all.c
index 64f46c8..0c94637 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -2002,7 +2002,7 @@ int kvm_cpu_exec(CPUState *cpu)
             case KVM_SYSTEM_EVENT_CRASH:
                 kvm_cpu_synchronize_state(cpu);
                 qemu_mutex_lock_iothread();
-                qemu_system_guest_panicked();
+                qemu_system_guest_panicked(cpu_get_crash_info(cpu));
                 qemu_mutex_unlock_iothread();
                 ret = 0;
                 break;
diff --git a/qapi/event.json b/qapi/event.json
index 7bf539b..970ff02 100644
--- a/qapi/event.json
+++ b/qapi/event.json
@@ -488,7 +488,9 @@
 #
 # @action: action that has been taken, currently always "pause"
 #
-# Since: 1.5
+# @info: optional information about a panic
+#
+# Since: 1.5 (@info since 2.9)
 #
 # Example:
 #
@@ -497,7 +499,7 @@
 #
 ##
 { 'event': 'GUEST_PANICKED',
-  'data': { 'action': 'GuestPanicAction' } }
+  'data': { 'action': 'GuestPanicAction', '*info': 'GuestPanicInformation' } }
 
 ##
 # @QUORUM_FAILURE:
diff --git a/qom/cpu.c b/qom/cpu.c
index d57faf3..5158f31 100644
--- a/qom/cpu.c
+++ b/qom/cpu.c
@@ -218,6 +218,17 @@ static bool cpu_common_exec_interrupt(CPUState *cpu, int int_req)
     return false;
 }
 
+GuestPanicInformation *cpu_get_crash_info(CPUState *cpu)
+{
+    CPUClass *cc = CPU_GET_CLASS(cpu);
+    GuestPanicInformation *res = NULL;
+
+    if (cc->get_crash_info) {
+        res = cc->get_crash_info(cpu);
+    }
+    return res;
+}
+
 void cpu_dump_state(CPUState *cpu, FILE *f, fprintf_function cpu_fprintf,
                     int flags)
 {
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 71aa91f..fd7add2 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -3734,6 +3734,7 @@ static void x86_cpu_common_class_init(ObjectClass *oc, void *data)
     cc->do_interrupt = x86_cpu_do_interrupt;
     cc->cpu_exec_interrupt = x86_cpu_exec_interrupt;
     cc->dump_state = x86_cpu_dump_state;
+    cc->get_crash_info = x86_cpu_get_crash_info;
     cc->set_pc = x86_cpu_set_pc;
     cc->synchronize_from_tb = x86_cpu_synchronize_from_tb;
     cc->gdb_read_register = x86_cpu_gdb_read_register;
diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
index 6ed3876..2536780 100644
--- a/target/s390x/kvm.c
+++ b/target/s390x/kvm.c
@@ -1864,7 +1864,7 @@ static void unmanageable_intercept(S390CPU *cpu, const char *str, int pswoffset)
                  str, cs->cpu_index, ldq_phys(cs->as, cpu->env.psa + pswoffset),
                  ldq_phys(cs->as, cpu->env.psa + pswoffset + 8));
     s390_cpu_halt(cpu);
-    qemu_system_guest_panicked();
+    qemu_system_guest_panicked(NULL);
 }
 
 static int handle_intercept(S390CPU *cpu)
@@ -1897,7 +1897,7 @@ static int handle_intercept(S390CPU *cpu)
                 if (is_special_wait_psw(cs)) {
                     qemu_system_shutdown_request();
                 } else {
-                    qemu_system_guest_panicked();
+                    qemu_system_guest_panicked(NULL);
                 }
             }
             r = EXCP_HALTED;
diff --git a/vl.c b/vl.c
index b4eaf03..d68254b 100644
--- a/vl.c
+++ b/vl.c
@@ -1707,18 +1707,23 @@ void qemu_system_reset(bool report)
     cpu_synchronize_all_post_reset();
 }
 
-void qemu_system_guest_panicked(void)
+void qemu_system_guest_panicked(GuestPanicInformation *info)
 {
     if (current_cpu) {
         current_cpu->crash_occurred = true;
     }
-    qapi_event_send_guest_panicked(GUEST_PANIC_ACTION_PAUSE, &error_abort);
+    qapi_event_send_guest_panicked(GUEST_PANIC_ACTION_PAUSE,
+                                   !!info, info, &error_abort);
     vm_stop(RUN_STATE_GUEST_PANICKED);
     if (!no_shutdown) {
         qapi_event_send_guest_panicked(GUEST_PANIC_ACTION_POWEROFF,
-                                       &error_abort);
+                                       !!info, info, &error_abort);
         qemu_system_shutdown_request();
     }
+
+    if (info) {
+        qapi_free_GuestPanicInformation(info);
+    }
 }
 
 void qemu_system_reset_request(void)
-- 
2.7.4

[Qemu-devel] [PATCH v4 3/3] vl: log available guest crash information

[Denis V. Lunev]

From: Anton Nefedov <anton.nefedov@virtuozzo.com>

There is a suitable log mask for the purpose.

Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
---
 vl.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/vl.c b/vl.c
index d68254b..903c46d 100644
--- a/vl.c
+++ b/vl.c
@@ -1709,6 +1709,8 @@ void qemu_system_reset(bool report)
 
 void qemu_system_guest_panicked(GuestPanicInformation *info)
 {
+    qemu_log_mask(LOG_GUEST_ERROR, "Guest crashed\n");
+
     if (current_cpu) {
         current_cpu->crash_occurred = true;
     }
@@ -1722,6 +1724,15 @@ void qemu_system_guest_panicked(GuestPanicInformation *info)
     }
 
     if (info) {
+        if (info->type == GUEST_PANIC_INFORMATION_KIND_HYPER_V) {
+            qemu_log_mask(LOG_GUEST_ERROR, "HV crash parameters: (%#"PRIx64
+                          " %#"PRIx64" %#"PRIx64" %#"PRIx64" %#"PRIx64")\n",
+                          info->u.hyper_v.data->arg1,
+                          info->u.hyper_v.data->arg2,
+                          info->u.hyper_v.data->arg3,
+                          info->u.hyper_v.data->arg4,
+                          info->u.hyper_v.data->arg5);
+        }
         qapi_free_GuestPanicInformation(info);
     }
 }
-- 
2.7.4

Re: [Qemu-devel] [PATCH v3 0/3] kvm: report available guest crash parameters

[Paolo Bonzini]

On 14/02/2017 07:25, Denis V. Lunev wrote:
> Windows reports BSOD parameters through Hyper-V crash MSRs. This
> information is very useful for initial crash analysis and thus
> it would be nice to see it in the QEMU log file. There is suitable
> log mask for the purpose.
> 
> Linux guest does not provide this information, but still it would
> be nice to log that we have crashed.
> 
> Changes from v3:
> - existing kvm_cpu_synchronize_state() used to fetch HV crash MSRs
>   (hence, no separate storage for these MSRs in struct X86CPU anymore)

Nice. :)

> - qapi_free_GuestPanicInformation() used to release memory
> 
> Changes from v2:
> - fixed PPC compilation
> 
> Changes since v1:
> - patches resplit
> - created property to query crash parameters
> - crash parameters added to panic event
> 
> Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com>
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Paolo Bonzini <pbonzini@redhat.com>
> CC: Marcelo Tosatti <mtosatti@redhat.com>
> CC: Richard Henderson <rth@twiddle.net>
> CC: Eduardo Habkost <ehabkost@redhat.com>
> CC: Eric Blake <eblake@redhat.com>
> CC: Markus Armbruster <armbru@redhat.com>
> 
> Anton Nefedov (3):
>   i386/cpu: add crash-information QOM property
>   report guest crash information in GUEST_PANICKED event
>   vl: log available guest crash information
> 
>  hw/misc/pvpanic.c       |  2 +-
>  hw/ppc/spapr_rtas.c     |  3 ++-
>  include/qom/cpu.h       | 10 +++++++++
>  include/sysemu/kvm.h    |  2 ++
>  include/sysemu/sysemu.h |  2 +-
>  kvm-all.c               |  3 ++-
>  qapi-schema.json        | 24 +++++++++++++++++++++
>  qapi/event.json         |  6 ++++--
>  qom/cpu.c               | 11 ++++++++++
>  stubs/Makefile.objs     |  1 +
>  stubs/kvm-crash.c       |  8 +++++++
>  target/i386/cpu.c       | 55 +++++++++++++++++++++++++++++++++++++++++++++++++
>  target/i386/cpu.h       |  3 +++
>  target/i386/kvm.c       | 41 ++++++++++++++++++++++++++++++++++++
>  target/s390x/kvm.c      |  4 ++--
>  vl.c                    | 23 ++++++++++++++++++---
>  16 files changed, 187 insertions(+), 11 deletions(-)
>  create mode 100644 stubs/kvm-crash.c
> 

Queued for 2.9, thanks!

Paolo

Re: [Qemu-devel] [PATCH v4 1/3] i386/cpu: add crash-information QOM property

[Eric Blake]

[-- Attachment #1: Type: text/plain, Size: 1400 bytes --]

On 02/14/2017 12:25 AM, Denis V. Lunev wrote:
> From: Anton Nefedov <anton.nefedov@virtuozzo.com>
> 
> Windows reports BSOD parameters through Hyper-V crash MSRs. This
> information is very useful for initial crash analysis and thus
> it would be nice to have a way to fetch it.
> 
> Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com>
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> ---

> +++ b/qapi-schema.json
> @@ -5846,6 +5846,30 @@
>    'data': [ 'pause', 'poweroff' ] }
>  
>  ##
> +# @GuestPanicInformation:
> +#
> +# Information about a guest panic
> +#
> +# Since: 2.9
> +##
> +{'union': 'GuestPanicInformation',
> + 'data': { 'hyper-v': 'GuestPanicInformationHyperV' } }
> +

Markus has been trying to eliminate the addition of new "simple unions"
- while they are syntactically shorter in the .json file, they are
bulkier over the wire with extra {} nesting, and more verbose in the C
code, when compared to using a flat union instead.  I won't necessarily
hold up this patch as-is, but if we are going to avoid new simple
unions, we have to change this before 2.9 bakes in the {} nesting (we
can convert a simple union to a flat union without breaking QMP
back-compat, but it's messier than if we avoid the nesting to begin with).

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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Re: [Qemu-devel] [PATCH v4 2/3] report guest crash information in GUEST_PANICKED event

[Eric Blake]

[-- Attachment #1: Type: text/plain, Size: 1033 bytes --]

On 02/14/2017 12:25 AM, Denis V. Lunev wrote:
> From: Anton Nefedov <anton.nefedov@virtuozzo.com>
> 
> it's not very convenient to use the crash-information property interface,
> so provide a CPU class callback to get the guest crash information, and pass
> that information in the event
> 
> Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com>
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> ---

> +++ b/qapi/event.json
> @@ -488,7 +488,9 @@
>  #
>  # @action: action that has been taken, currently always "pause"
>  #
> -# Since: 1.5
> +# @info: optional information about a panic
> +#
> +# Since: 1.5 (@info since 2.9)

This is more usually written:

# @info: #optional information about a panic (since 2.9)
#
# Since: 1.5


> +
> +    if (info) {
> +        qapi_free_GuestPanicInformation(info);

qapi_free_*() is safe to call on a NULL pointer, so this is a useless 'if'.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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Re: [Qemu-devel] [PATCH v4 1/3] i386/cpu: add crash-information QOM property

[Markus Armbruster]

Eric Blake <eblake@redhat.com> writes:

> On 02/14/2017 12:25 AM, Denis V. Lunev wrote:
>> From: Anton Nefedov <anton.nefedov@virtuozzo.com>
>> 
>> Windows reports BSOD parameters through Hyper-V crash MSRs. This
>> information is very useful for initial crash analysis and thus
>> it would be nice to have a way to fetch it.
>> 
>> Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com>
>> Signed-off-by: Denis V. Lunev <den@openvz.org>
>> ---
>
>> +++ b/qapi-schema.json
>> @@ -5846,6 +5846,30 @@
>>    'data': [ 'pause', 'poweroff' ] }
>>  
>>  ##
>> +# @GuestPanicInformation:
>> +#
>> +# Information about a guest panic
>> +#
>> +# Since: 2.9
>> +##
>> +{'union': 'GuestPanicInformation',
>> + 'data': { 'hyper-v': 'GuestPanicInformationHyperV' } }
>> +
>
> Markus has been trying to eliminate the addition of new "simple unions"
> - while they are syntactically shorter in the .json file, they are
> bulkier over the wire with extra {} nesting, and more verbose in the C
> code, when compared to using a flat union instead.  I won't necessarily
> hold up this patch as-is, but if we are going to avoid new simple
> unions, we have to change this before 2.9 bakes in the {} nesting (we
> can convert a simple union to a flat union without breaking QMP
> back-compat, but it's messier than if we avoid the nesting to begin with).

We should not add new simple unions.  Please have a look at my
"[PATCH 0/2] Flatten simple unions where we still can".

Message-Id: <1486569864-17005-1-git-send-email-armbru@redhat.com>
https://lists.gnu.org/archive/html/qemu-devel/2017-02/msg01689.html

Re: [Qemu-devel] [PATCH v4 1/3] i386/cpu: add crash-information QOM property

[Daniel P. Berrange]

On Tue, Feb 14, 2017 at 09:25:22AM +0300, Denis V. Lunev wrote:
> From: Anton Nefedov <anton.nefedov@virtuozzo.com>
> 
> Windows reports BSOD parameters through Hyper-V crash MSRs. This
> information is very useful for initial crash analysis and thus
> it would be nice to have a way to fetch it.
> 
> Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com>
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> ---
>  kvm-all.c         |  1 +
>  qapi-schema.json  | 24 ++++++++++++++++++++++++
>  target/i386/cpu.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 75 insertions(+)
> 
> diff --git a/kvm-all.c b/kvm-all.c
> index a27c880..64f46c8 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -2000,6 +2000,7 @@ int kvm_cpu_exec(CPUState *cpu)
>                  ret = EXCP_INTERRUPT;
>                  break;
>              case KVM_SYSTEM_EVENT_CRASH:
> +                kvm_cpu_synchronize_state(cpu);
>                  qemu_mutex_lock_iothread();
>                  qemu_system_guest_panicked();
>                  qemu_mutex_unlock_iothread();
> diff --git a/qapi-schema.json b/qapi-schema.json
> index cbdffdd..9cb6ac5 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -5846,6 +5846,30 @@
>    'data': [ 'pause', 'poweroff' ] }
>  
>  ##
> +# @GuestPanicInformation:
> +#
> +# Information about a guest panic
> +#
> +# Since: 2.9
> +##
> +{'union': 'GuestPanicInformation',
> + 'data': { 'hyper-v': 'GuestPanicInformationHyperV' } }
> +
> +##
> +# @GuestPanicInformationHyperV:
> +#
> +# Hyper-V specific guest panic information (HV crash MSRs)
> +#
> +# Since: 2.9
> +##
> +{'struct': 'GuestPanicInformationHyperV',
> + 'data': { 'arg1': 'uint64',
> +           'arg2': 'uint64',
> +           'arg3': 'uint64',
> +           'arg4': 'uint64',
> +           'arg5': 'uint64' } }

Is there any benefit in naming these fields ?  In the Linux kernel
they are filled with ip, ax, bx, cx, dx register values. I'm unclear
if that's defined standard semantics by Microsoft, and thus consistent
for all OS using this interface, or just what Linux happens to store
there ?  If they're standard, then IMHO it could be nicer to name the
QAPI fields  ip, ax, bx, cx, dx.


Regards,
Daniel
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