Re: [Qemu-devel] [RFC] qemu-ga: Introduce guest-hibernate command

[Michael Roth]

On 12/08/2011 12:52 PM, Luiz Capitulino wrote:
> This is basically suspend to disk on a Linux guest.

Nice!

> Signed-off-by: Luiz Capitulino<address@hidden>
> ---
>
> This is an RFC because I did it as simple as possible and I'm open to
> suggestions...
>
> Now, while testing this or even "echo disk>  /sys/power/state" I get several
> funny results. Some times qemu just dies after printing that message:
>
>   "Guest moved used index from 20151 to 1"
>
> Some times it doesn't die, but I'm unable to log into the guest: I type
> username&  password but the terminal kind of locks (the shell doesn't run).

Triggered this pretty easily on FC15 amd64:

qemu-system-x86_64: Guest moved used index from 13024 to 80

I'll see if I can get a trace of what's happening on my end.

> Some times it works...
>
>   qapi-schema-guest.json     |   11 +++++++++++
>   qga/guest-agent-commands.c |   19 +++++++++++++++++++
>   2 files changed, 30 insertions(+), 0 deletions(-)
>
> diff --git a/qapi-schema-guest.json b/qapi-schema-guest.json
> index fde5971..2c5bbcf 100644
> --- a/qapi-schema-guest.json
> +++ b/qapi-schema-guest.json
> @@ -215,3 +215,14 @@
>   ##
>   { 'command': 'guest-fsfreeze-thaw',
>     'returns': 'int' }
> +
> +##
> +# @guest-hibernate
> +#
> +# Save RAM contents to disk and powerdown the guest.
> +#
> +# Notes: This command doesn't return on success.
> +#
> +# Since: 1.1
> +##
> +{ 'command': 'guest-hibernate' }
> diff --git a/qga/guest-agent-commands.c b/qga/guest-agent-commands.c
> index 6da9904..9dd4060 100644
> --- a/qga/guest-agent-commands.c
> +++ b/qga/guest-agent-commands.c
> @@ -550,6 +550,25 @@ int64_t qmp_guest_fsfreeze_thaw(Error **err)
>   }
>   #endif
>
> +#define LINUX_SYS_STATE_FILE "/sys/power/state"
> +
> +void qmp_guest_hibernate(Error **err)
> +{
> +    int fd;
> +
> +    fd = open(LINUX_SYS_STATE_FILE, O_WRONLY);
> +    if (fd<  0) {
> +        error_set(err, QERR_OPEN_FILE_FAILED, LINUX_SYS_STATE_FILE);
> +        return;
> +    }
> +
> +    if (write(fd, "disk", 4)<  0) {
> +        error_set(err, QERR_UNDEFINED_ERROR);
> +    }

There's basically no chance of this returning, so we should issue it 
asynchronously like we do with qmp_guest_shutdown(). Also agreed on 
Daniel's point that we should use pm-hibernate, but failing back to this 
should be okay...assuming the virtio issue isn't indicative of some 
fundamental problem with that approach...

> +
> +    close(fd);
> +}
> +
>   /* register init/cleanup routines for stateful command groups */
>   void ga_command_state_init(GAState *s, GACommandState *cs)
>   {