[Qemu-devel] [PATH v2 0/2] qmp: 'wakeup-suspend-support' in query-target

[Qemu-devel] [PATH v2 0/2] qmp: 'wakeup-suspend-support' in query-target

[Daniel Henrique Barboza]

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        |  3 ++-
 qga/qapi-schema.json    | 14 ++++++++++----
 vl.c                    |  5 +++++
 5 files changed, 19 insertions(+), 5 deletions(-)

-- 
2.13.6

[Qemu-devel] [PATCH v2 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}}

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        | 3 ++-
 vl.c                    | 5 +++++
 4 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch_init.c b/arch_init.c
index a0b8ed6167..9c5c519d9d 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -109,6 +109,7 @@ 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 31612caf10..b15374e0b8 100644
--- a/include/sysemu/sysemu.h
+++ b/include/sysemu/sysemu.h
@@ -69,6 +69,7 @@ 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 5c06745c79..6ed741d00b 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -2388,11 +2388,12 @@
 # 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: 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 d3a5c5d021..871c1f9bd1 100644
--- a/vl.c
+++ b/vl.c
@@ -1844,6 +1844,11 @@ 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;
-- 
2.13.6

[Qemu-devel] [PATCH v2 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>
---
 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:
-- 
2.13.6

Re: [Qemu-devel] [PATCH v2 1/2] qmp: adding 'wakeup-suspend-support' in query-target

[Eric Blake]

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On 01/02/2018 11:09 AM, Daniel Henrique Barboza wrote:
> 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
> 
...
> 
> 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>
> ---

Only an interface review:

>  arch_init.c             | 1 +
>  include/sysemu/sysemu.h | 1 +
>  qapi-schema.json        | 3 ++-
>  vl.c                    | 5 +++++
>  4 files changed, 9 insertions(+), 1 deletion(-)
> 

> +++ b/qapi-schema.json
> @@ -2388,11 +2388,12 @@
>  # 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

Missing a '(since 2.12)' notation.

>  #
>  # Since: 1.2.0
>  ##
>  { 'struct': 'TargetInfo',
> -  'data': { 'arch': 'str' } }
> +  'data': { 'arch': 'str', 'wakeup-suspend-support': 'bool' } }

The struct is output-only, so adding the new field unconditionally is
backwards-compatible.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


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Re: [Qemu-devel] [PATCH v2 1/2] qmp: adding 'wakeup-suspend-support' in query-target

[Daniel Henrique Barboza]

On 01/02/2018 06:06 PM, Eric Blake wrote:
> On 01/02/2018 11:09 AM, Daniel Henrique Barboza wrote:
>> 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
>>
> ...
>> 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>
>> ---
> Only an interface review:
>
>>   arch_init.c             | 1 +
>>   include/sysemu/sysemu.h | 1 +
>>   qapi-schema.json        | 3 ++-
>>   vl.c                    | 5 +++++
>>   4 files changed, 9 insertions(+), 1 deletion(-)
>>
>> +++ b/qapi-schema.json
>> @@ -2388,11 +2388,12 @@
>>   # 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
> Missing a '(since 2.12)' notation.

TargetInfo is marked as "Since 1.2.0".  Should I add the 2.12.0 notation 
to the
new parameter or change the 1.2.0 notation of TargetInfo?

>
>>   #
>>   # Since: 1.2.0
>>   ##
>>   { 'struct': 'TargetInfo',
>> -  'data': { 'arch': 'str' } }
>> +  'data': { 'arch': 'str', 'wakeup-suspend-support': 'bool' } }
> The struct is output-only, so adding the new field unconditionally is
> backwards-compatible.
>
I believe it's worth adding this info in the commit message.


Thanks,

Daniel

Re: [Qemu-devel] [PATCH v2 1/2] qmp: adding 'wakeup-suspend-support' in query-target

[Eric Blake]

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On 01/02/2018 02:28 PM, Daniel Henrique Barboza wrote:

>>> 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>
>>> ---
>> Only an interface review:
>>

>>> @@ -2388,11 +2388,12 @@
>>>   # 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
>> Missing a '(since 2.12)' notation.
> 
> TargetInfo is marked as "Since 1.2.0".  Should I add the 2.12.0 notation
> to the
> new parameter or change the 1.2.0 notation of TargetInfo?

Just on the new field, as in:

##
# @TargetInfo:
#
# 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
##

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


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