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

["Daniel P. Berrange" <berrange@redhat.com>]

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.

[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
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