Re: [libvirt] [Qemu-devel] [PATCH v7 1/3] qmp: adding 'wakeup-suspend-support' in query-target

Cc'ing a few more people. Daniel Henrique Barboza <danielhb(a)linux.ibm.com&gt; writes: > 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). > > Reported-by: Balamuruhan S <bala24(a)linux.vnet.ibm.com&gt; > Signed-off-by: Daniel Henrique Barboza <danielhb(a)linux.ibm.com&gt; Is query-target is the right place to carry this flag? v7 is rather late for this kind of question; my sincere apologies.

Issue#2: the flag isn't a property of the target. Due to -no-acpi, it's not even a property of the machine type. If it was, query-machines would be the natural owner of the flag. Perhaps query-machines is still the proper owner. The value of wakeup-suspend-support would have to depend on -no-acpi for the machine types that honor it. Not ideal; I'd prefer MachineInfo to be static. Tolerable? I guess that's also a libvirt question.