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

[Lei Li <lilei@linux.vnet.ibm.com>]

On 03/02/2013 01:38 AM, Eric Blake wrote:
> On 03/01/2013 02:33 AM, Lei Li wrote:
>> Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
>> ---
>>   qga/commands-posix.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>>   qga/qapi-schema.json | 27 ++++++++++++++++++++++++++
>>   2 files changed, 82 insertions(+)
>>
>> diff --git a/qga/commands-posix.c b/qga/commands-posix.c
>> index f159e25..e246a0d 100644
>> --- a/qga/commands-posix.c
>> +++ b/qga/commands-posix.c
>> @@ -135,6 +135,61 @@ 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 ((sizeof(time_t) <= 4) && ((unsigned long) time_ns & (1ul << 31))) {
> Wrong.  If 'unsigned long' and 'time_t' are both 32 bits, but time_ns is
> 0x1000000000000000, then the cast truncates to 0 and you don't report
> overflow.  Conversely, if time_ns is 0x80000000, you report overflow,
> even though this value fits in 32-bit time_t after you do division from
> nanoseconds back to seconds.  What you WANT is:

Yes, you are right.. thanks.

>
> if (time_ns / 1000000000 != (time_t)(time_ns / 1000000000)) {
>
>> +        error_setg_errno(errp, errno, "Invalid time %ld for overflow",
>> +                         time_ns);
> That wording sounds awkward.  Worse, errno is NOT set to anything sane,
> so you do NOT want error_setg_errno.  And %ld is wrong for int64_t on
> 32-bit platforms.  How about:
>
> error_setg(errp, "Time %" PRI64D " is too large", time_ns);

Sure, will address it as the your later reply.

>> +++ b/qga/qapi-schema.json
>> @@ -99,6 +99,33 @@
>>     'returns': 'int' }
>>   
>>   ##
>> +# @guest-set-time:
>> +#
>> +# Set guest time.
>> +#
>> +# Right now, when a guest is paused or migrated to a file
> s/Right now, when/When/
>
>> +# then loaded from that file, the guest OS has no idea that
>> +# there was a big gap in the time. Depending on how long
>> +# the gap was, NTP might not be able to resynchronize the
>> +# guest.
>> +#
>> +# This command tries to set guest time based on the information
>> +# from host or an absolute value given by management app, and
>> +# set the Hardware Clock to the current System Time. This
>> +# 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/GMT.
> drop '/GMT'
>
>> +#
>> +# Returns: Nothing on success.
>> +#
>> +# Since: 1.5
>> +##
>> +{ 'command': 'guest-set-time',
>> +  'data': { 'time': 'int' } }
>> +
>> +##
>>   # @GuestAgentCommandInfo:
>>   #
>>   # Information about guest agent commands.
>>


-- 
Lei