Re: [Qemu-devel] [PATCH 2/2] qga: add guest-set-time command

[Eric Blake <eblake@redhat.com>]

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On 03/04/2013 02:16 AM, Lei Li wrote:
> Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
> ---
>  qga/commands-posix.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  qga/qapi-schema.json | 27 ++++++++++++++++++++++++++
>  2 files changed, 81 insertions(+)
> 
> diff --git a/qga/commands-posix.c b/qga/commands-posix.c
> index 6fc6003..0515f5f 100644
> --- a/qga/commands-posix.c
> +++ b/qga/commands-posix.c
> @@ -135,6 +135,60 @@ int64_t qmp_guest_get_time(Error **errp)
>     return time_ns;
>  }
>  
> +void qmp_guest_set_time(int64_t time_ns, Error **errp)
> +{
> +    int ret;
> +    int status;
> +    pid_t pid;
> +    Error *local_err = NULL;
> +    struct timeval tv;
> +
> +    /* year-2038 will overflow in case time_t is 32bit */
> +    if (time_ns / 1000000000 != (time_t)(time_ns / 1000000000)) {
> +        error_setg(errp, "Time %" PRId64 " is too large", time_ns);

You set the error, but then fall through...

> +    }
> +
> +    tv.tv_sec = time_ns / 1000000000;
> +    tv.tv_usec = (time_ns % 1000000000) / 1000;
> +
> +    ret = settimeofday(&tv, NULL);

...and change the guest time to an invalid value anyways.  This could
cause the guest to severely misbehave.

> +    if (ret < 0) {
> +        error_setg_errno(errp, errno, "Failed to set time to guest");
> +        return;

You should have done an early exit on the other error, like you did here.

> +#
> +# This command tries to set guest time based on the information
> +# from host or an absolute value given by management app, and

The absolute value given by the management app _is_ information from the
host.  I'd simplify this to just:

This command tries to set guest time to the given value, then

> +# set the Hardware Clock to the current System Time. This

s/set/sets/

> +# will make it easier for a guest to resynchronize without
> +# waiting for NTP.
> +#
> +# @time: time of nanoseconds, relative to the Epoch of
> +#        1970-01-01 in UTC.
> +#

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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