[Qemu-devel] [PATCH v5 0/2] qmp: 'wakeup-suspend-support' in query-target

[Qemu-devel] [PATCH v5 0/2] qmp: 'wakeup-suspend-support' in query-target

[Daniel Henrique Barboza]

v5:
- removed a paragraph in the recently added qemu_register_wakeup_notifier
comment that was added. That paragraph was adding too much in-depth
information about the current design of the system_wakeup, making it
harder to understand the whole point (suggested by Mike Roth).
- previous version link:
https://lists.nongnu.org/archive/html/qemu-devel/2018-01/msg00879.html 

v4:
- added a comment in 'qemu_register_wakeup_notifier' about the effects
of adding a wakeup notifier without proper suspend/wakeup support in the
logic of the new wakeup-suspend-support flag, as suggested by Mike Roth
- previous version link:
https://lists.gnu.org/archive/html/qemu-devel/2018-01/msg00358.html

v3:
- added a "(since 2.12)" notation in the new flag, as suggested by
Eric Blake
- added a "backwards compatible" note in the commit msg
- previous version link:
https://lists.gnu.org/archive/html/qemu-devel/2018-01/msg00093.html

v2:
- changed the approach based on v1 discussions: instead of a new API, add
the required flag in QMP query-target
- dropped patch 2 since query-target does not have an HMP counterpart
- previous version link:
https://lists.gnu.org/archive/html/qemu-devel/2017-12/msg00889.html


Daniel Henrique Barboza (2):
  qmp: adding 'wakeup-suspend-support' in query-target
  qga: update guest-suspend-ram and guest-suspend-hybrid descriptions

 arch_init.c             |  1 +
 include/sysemu/sysemu.h |  1 +
 qapi-schema.json        |  4 +++-
 qga/qapi-schema.json    | 14 ++++++++++----
 vl.c                    | 21 +++++++++++++++++++++
 5 files changed, 36 insertions(+), 5 deletions(-)

-- 
2.14.3

[Qemu-devel] [PATCH v5 1/2] qmp: adding 'wakeup-suspend-support' in query-target

[Daniel Henrique Barboza]

When issuing the qmp/hmp 'system_wakeup' command, what happens in a
nutshell is:

- qmp_system_wakeup_request set runstate to RUNNING, sets a wakeup_reason
and notify the event
- in the main_loop, all vcpus are paused, a system reset is issued, all
subscribers of wakeup_notifiers receives a notification, vcpus are then
resumed and the wake up QAPI event is fired

Note that this procedure alone doesn't ensure that the guest will awake
from SUSPENDED state - the subscribers of the wake up event must take
action to resume the guest, otherwise the guest will simply reboot.

At this moment there are only two subscribers of the wake up event: one
in hw/acpi/core.c and another one in hw/i386/xen/xen-hvm.c. This means
that system_wakeup does not work as intended with other architectures.

However, only the presence of 'system_wakeup' is required for QGA to
support 'guest-suspend-ram' and 'guest-suspend-hybrid' at this moment.
This means that the user/management will expect to suspend the guest using
one of those suspend commands and then resume execution using system_wakeup,
regardless of the support offered in system_wakeup in the first place.

This patch adds a new flag called 'wakeup-suspend-support' in TargetInfo
that allows the caller to query if the guest supports wake up from
suspend via system_wakeup. It goes over the subscribers of the wake up
event and, if it's empty, it assumes that the guest does not support
wake up from suspend (and thus, pm-suspend itself).

This is the expected output of query-target when running a x86 guest:

{"execute" : "query-target"}
{"return": {"arch": "x86_64", "wakeup-suspend-support": true}}

This is the output when running a pseries guest:

{"execute" : "query-target"}
{"return": {"arch": "ppc64", "wakeup-suspend-support": false}}

Given that the TargetInfo structure is read-only, adding a new flag to
it is backwards compatible. There is no need to deprecate the old
TargetInfo format.

With this extra tool, management can avoid situations where a guest
that does not have proper suspend/wake capabilities ends up in
inconsistent state (e.g.
https://github.com/open-power-host-os/qemu/issues/31).

Signed-off-by: Daniel Henrique Barboza <danielhb@linux.vnet.ibm.com>
---
 arch_init.c             |  1 +
 include/sysemu/sysemu.h |  1 +
 qapi-schema.json        |  4 +++-
 vl.c                    | 21 +++++++++++++++++++++
 4 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/arch_init.c b/arch_init.c
index 4c36f2b076..72846866cf 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -111,6 +111,7 @@ TargetInfo *qmp_query_target(Error **errp)
     TargetInfo *info = g_malloc0(sizeof(*info));
 
     info->arch = g_strdup(TARGET_NAME);
+    info->wakeup_suspend_support = !qemu_wakeup_notifier_is_empty();
 
     return info;
 }
diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
index 77bb3da582..7620220a4b 100644
--- a/include/sysemu/sysemu.h
+++ b/include/sysemu/sysemu.h
@@ -67,6 +67,7 @@ typedef enum WakeupReason {
 void qemu_system_reset_request(ShutdownCause reason);
 void qemu_system_suspend_request(void);
 void qemu_register_suspend_notifier(Notifier *notifier);
+bool qemu_wakeup_notifier_is_empty(void);
 void qemu_system_wakeup_request(WakeupReason reason);
 void qemu_system_wakeup_enable(WakeupReason reason, bool enabled);
 void qemu_register_wakeup_notifier(Notifier *notifier);
diff --git a/qapi-schema.json b/qapi-schema.json
index 0262b9f20b..939af3b76f 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -2388,11 +2388,13 @@
 # Information describing the QEMU target.
 #
 # @arch: the target architecture (eg "x86_64", "i386", etc)
+# @wakeup-suspend-support: true if the target supports wake up from
+#                          suspend (since 2.12)
 #
 # Since: 1.2.0
 ##
 { 'struct': 'TargetInfo',
-  'data': { 'arch': 'str' } }
+  'data': { 'arch': 'str', 'wakeup-suspend-support': 'bool' } }
 
 ##
 # @query-target:
diff --git a/vl.c b/vl.c
index 81724f5f17..d9f197d85e 100644
--- a/vl.c
+++ b/vl.c
@@ -1825,11 +1825,32 @@ void qemu_system_wakeup_enable(WakeupReason reason, bool enabled)
     }
 }
 
+/* The existence of a wake-up notifier is being checked in the function
+ * qemu_wakeup_notifier_is_empty and it's used in the logic of the
+ * wakeup-suspend-support flag of QMP 'query-target' command. The idea
+ * of this flag is to indicate whether the guest supports wake-up from
+ * suspend (via system_wakeup QMP/HMP call for example), warning the user
+ * that the guest can't handle both wake-up from suspend and the suspend
+ * itself via QGA guest-suspend-ram and guest-suspend-hybrid (if it
+ * can't wake up, it can't be suspended safely).
+ *
+ * An assumption is made by the wakeup-suspend-support flag that only the
+ * guests that can go to RUN_STATE_SUSPENDED and wake up properly would
+ * be interested in this wakeup_notifier. Adding a wakeup_notifier for
+ * any other reason will break the logic of the wakeup-suspend-support
+ * flag and can lead to user/management confusion about the suspend/wake-up
+ * support of the guest.
+ */
 void qemu_register_wakeup_notifier(Notifier *notifier)
 {
     notifier_list_add(&wakeup_notifiers, notifier);
 }
 
+bool qemu_wakeup_notifier_is_empty(void)
+{
+    return QLIST_EMPTY(&wakeup_notifiers.notifiers);
+}
+
 void qemu_system_killed(int signal, pid_t pid)
 {
     shutdown_signal = signal;
-- 
2.14.3

[Qemu-devel] [PATCH v5 2/2] qga: update guest-suspend-ram and guest-suspend-hybrid descriptions

[Daniel Henrique Barboza]

This patch updates the descriptions of 'guest-suspend-ram' and
'guest-suspend-hybrid' to mention that both commands relies now
on the existence of 'system_wakeup' and also on the proper support
for wake up from suspend, retrieved by the 'wakeup-suspend-support'
attribute of the 'query-target' QMP command.

Signed-off-by: Daniel Henrique Barboza <danielhb@linux.vnet.ibm.com>
Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
---
 qga/qapi-schema.json | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/qga/qapi-schema.json b/qga/qapi-schema.json
index 17884c7c70..e3fb8adfce 100644
--- a/qga/qapi-schema.json
+++ b/qga/qapi-schema.json
@@ -566,8 +566,11 @@
 # package installed in the guest.
 #
 # IMPORTANT: guest-suspend-ram requires QEMU to support the 'system_wakeup'
-# command.  Thus, it's *required* to query QEMU for the presence of the
-# 'system_wakeup' command before issuing guest-suspend-ram.
+# command and the guest to support wake up from suspend. Thus, it's
+# *required* to query QEMU for the presence of the 'system_wakeup' command
+# and to verify that wake up from suspend is enabled by checking the
+# 'wakeup-suspend-support' flag of 'query-target' QMP command, before issuing
+# guest-suspend-ram.
 #
 # This command does NOT return a response on success. There are two options
 # to check for success:
@@ -593,8 +596,11 @@
 # This command requires the pm-utils package to be installed in the guest.
 #
 # IMPORTANT: guest-suspend-hybrid requires QEMU to support the 'system_wakeup'
-# command.  Thus, it's *required* to query QEMU for the presence of the
-# 'system_wakeup' command before issuing guest-suspend-hybrid.
+# command and the guest to support wake up from suspend. Thus, it's
+# *required* to query QEMU for the presence of the 'system_wakeup' command
+# and to verify that wake up from suspend is enabled by checking the
+# 'wakeup-suspend-support' flag of 'query-target' QMP command, before issuing
+# guest-suspend-hybrid.
 #
 # This command does NOT return a response on success. There are two options
 # to check for success:
-- 
2.14.3

Re: [Qemu-devel] [PATCH v5 0/2] qmp: 'wakeup-suspend-support' in query-target

[Daniel Henrique Barboza]

Ping

On 02/19/2018 11:12 AM, Daniel Henrique Barboza wrote:
> v5:
> - removed a paragraph in the recently added qemu_register_wakeup_notifier
> comment that was added. That paragraph was adding too much in-depth
> information about the current design of the system_wakeup, making it
> harder to understand the whole point (suggested by Mike Roth).
> - previous version link:
> https://lists.nongnu.org/archive/html/qemu-devel/2018-01/msg00879.html
>
> v4:
> - added a comment in 'qemu_register_wakeup_notifier' about the effects
> of adding a wakeup notifier without proper suspend/wakeup support in the
> logic of the new wakeup-suspend-support flag, as suggested by Mike Roth
> - previous version link:
> https://lists.gnu.org/archive/html/qemu-devel/2018-01/msg00358.html
>
> v3:
> - added a "(since 2.12)" notation in the new flag, as suggested by
> Eric Blake
> - added a "backwards compatible" note in the commit msg
> - previous version link:
> https://lists.gnu.org/archive/html/qemu-devel/2018-01/msg00093.html
>
> v2:
> - changed the approach based on v1 discussions: instead of a new API, add
> the required flag in QMP query-target
> - dropped patch 2 since query-target does not have an HMP counterpart
> - previous version link:
> https://lists.gnu.org/archive/html/qemu-devel/2017-12/msg00889.html
>
>
> Daniel Henrique Barboza (2):
>    qmp: adding 'wakeup-suspend-support' in query-target
>    qga: update guest-suspend-ram and guest-suspend-hybrid descriptions
>
>   arch_init.c             |  1 +
>   include/sysemu/sysemu.h |  1 +
>   qapi-schema.json        |  4 +++-
>   qga/qapi-schema.json    | 14 ++++++++++----
>   vl.c                    | 21 +++++++++++++++++++++
>   5 files changed, 36 insertions(+), 5 deletions(-)
>

Re: [Qemu-devel] [PATCH v5 0/2] qmp: 'wakeup-suspend-support' in query-target

[Markus Armbruster]

Daniel Henrique Barboza <danielhb@linux.vnet.ibm.com> writes:

> Ping

Michael, you reviewed v4 (at least in part), can you have a look?

Re: [Qemu-devel] [PATCH v5 0/2] qmp: 'wakeup-suspend-support' in query-target

[Markus Armbruster]

Markus Armbruster <armbru@redhat.com> writes:

> Daniel Henrique Barboza <danielhb@linux.vnet.ibm.com> writes:
>
>> Ping
>
> Michael, you reviewed v4 (at least in part), can you have a look?

Have these patches fallen through the cracks?

Re: [Qemu-devel] [PATCH v5 0/2] qmp: 'wakeup-suspend-support' in query-target

[Daniel Henrique Barboza]

On 05/14/2018 05:46 AM, Markus Armbruster wrote:
> Markus Armbruster <armbru@redhat.com> writes:
>
>> Daniel Henrique Barboza <danielhb@linux.vnet.ibm.com> writes:
>>
>>> Ping
>> Michael, you reviewed v4 (at least in part), can you have a look?
> Have these patches fallen through the cracks?
>
Should I re-send it? Not sure if this is applicable in the current code 
base anymore.



Daniel

Re: [Qemu-devel] [PATCH v5 0/2] qmp: 'wakeup-suspend-support' in query-target

[Markus Armbruster]

Daniel Henrique Barboza <danielhb@linux.ibm.com> writes:

> On 05/14/2018 05:46 AM, Markus Armbruster wrote:
>> Markus Armbruster <armbru@redhat.com> writes:
>>
>>> Daniel Henrique Barboza <danielhb@linux.vnet.ibm.com> writes:
>>>
>>>> Ping
>>> Michael, you reviewed v4 (at least in part), can you have a look?
>> Have these patches fallen through the cracks?
>>
> Should I re-send it? Not sure if this is applicable in the current
> code base anymore.

git-am isn't happy on current master.  The conflicts look simple enough
for a maintainer to resolve, but that's yet another hurdle.  Best to
respin, I think (assuming you still want the patches to go in).

Re: [Qemu-devel] [PATCH v5 0/2] qmp: 'wakeup-suspend-support' in query-target

[Daniel Henrique Barboza]

On 05/15/2018 02:29 AM, Markus Armbruster wrote:
> git-am isn't happy on current master.  The conflicts look simple enough
> for a maintainer to resolve, but that's yet another hurdle.  Best to
> respin, I think (assuming you still want the patches to go in).
Just respinned it to v6. Let's see how that goes.


Daniel