Re: [Qemu-devel] [PATCH v2] qemu-ga: Add the guest-suspend command

[Luiz Capitulino <lcapitulino@redhat.com>]

On Tue, 13 Dec 2011 23:13:23 +0000
"Daniel P. Berrange" <berrange@redhat.com> wrote:

> On Tue, Dec 13, 2011 at 04:28:50PM -0200, Luiz Capitulino wrote:
> > It supports two modes: "hibernate" (which corresponds to S4) and
> > "sleep" (which corresponds to S3). It will try to execute the
> > pm-hibernate or pm-suspend scripts, if the scripts don't exist
> > the command will try to suspend by directly writing to the
> > "/sys/power/state" file.
> > 
> > An interesting implementation detail is how to cleanup the child's
> > status on termination, so that we don't create zombies. I've
> > choosen to ignore the SIGCHLD signal. This will cause the kernel to
> > automatically cleanup the child's status on its termination.
> > 
> > Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
> > ---
> > 
> > I've tested this w/o any virtio driver, as they don't support S4 yet. For
> > S4 it seems to work ok. I couldn't fully test S3 because we lack a way to
> > resume from it, but by checking the logs it seems to work fine.
> > 
> > changelog
> > ---------
> > 
> > v2
> > 
> > o Rename the command to 'guest-suspend'
> > o Add 'mode' parameter
> > o Use pm-utils scripts
> > o Cleanup child termination status
> > 
> >  qapi-schema-guest.json     |   17 +++++++++++
> >  qemu-ga.c                  |   11 +++++++-
> >  qga/guest-agent-commands.c |   64 ++++++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 91 insertions(+), 1 deletions(-)
> > 
> > diff --git a/qapi-schema-guest.json b/qapi-schema-guest.json
> > index 29989fe..656bde9 100644
> > --- a/qapi-schema-guest.json
> > +++ b/qapi-schema-guest.json
> > @@ -219,3 +219,20 @@
> >  ##
> >  { 'command': 'guest-fsfreeze-thaw',
> >    'returns': 'int' }
> > +
> > +##
> > +# @guest-suspend
> > +#
> > +# Suspend guest execution by entering ACPI power state S3 or S4.
> > +#
> > +# @mode: 'hibernate' RAM content is saved in the disk and the guest is
> > +#                    powered down (this corresponds to ACPI S4)
> > +#        'sleep'     execution is suspended but the RAM retains its contents
> > +#                    (this corresponds to ACPI S3)
> 
> Standard pm-utils in Linux supports three ways to suspend these
> days, suspend, hibernate & suspend-hybrid. libvirt supports
> all 3 modes in our recently added API for suspending the physical
> host, so I think we'll want to also have all 3 for suspending
> guests too.

Ok.

> 
> [quote pm-suspend(8)]
>        pm-suspend
>            During suspend most devices are shutdown, and
>            system state is saved in RAM. The system still
>            requires power in this state. Most modern systems
>            require 3 to 5 seconds to enter and leave suspend,
>            and most laptops can stay in suspend mode for 1 to
>            3 days before exhausting their battery.
> 
>        pm-hibernate
>            During hibernate the system is fully powered off,
>            and system state is saved to disk. The system does
>            not require power, and can stay in hibernate mode
>            indefinitely. Most modern systems require 15 to 45
>            seconds to enter and leave hibernate, and entering
>            and leaving hibernate takes longer when you have
>            more memory.
> 
>        pm-suspend-hybrid
>            Hybrid-suspend is the process where the system does
>            everything it needs to hibernate, but suspends
>            instead of shutting down. This means that your
>            computer can wake up quicker than for normal
>            hibernation if you do not run out of power, and you
>            can resume even if you run out of power. s2both(8)
>            is an hybrid-suspend implementation.
> [/quote]
> 
> 
> > diff --git a/qga/guest-agent-commands.c b/qga/guest-agent-commands.c
> > index a09c8ca..4799638 100644
> > --- a/qga/guest-agent-commands.c
> > +++ b/qga/guest-agent-commands.c
> > @@ -574,6 +574,70 @@ int64_t qmp_guest_fsfreeze_thaw(Error **err)
> >  }
> >  #endif
> >  
> > +#define LINUX_PM_UTILS_PATH "/usr/sbin"
> > +#define LINUX_SYS_STATE_FILE "/sys/power/state"
> > +
> > +void qmp_guest_suspend(const char *mode, Error **err)
> > +{
> > +    int ret, fd = -1;
> > +    const char *pmutils_bin;
> > +    char pmutils_bin_path[PATH_MAX];
> > +
> > +    if (strcmp(mode, "hibernate") == 0) {
> > +        pmutils_bin = "pm-hibernate";
> > +    } else if (strcmp(mode, "sleep") == 0) {
> > +        pmutils_bin = "pm-suspend";
> 
> Here you'd just add pm-suspend-hybrid too
> 
> Regards,
> Daniel