Re: [Xen-devel] [PATCH] libxl: support for "rtc_timeoffset" and "localtime"

[Lin Ming <mlin@xxxxxxxxxxxxx>]

On Mon, Mar 19, 2012 at 5:57 AM, Teck Choon Giam
<giamteckchoon@xxxxxxxxx> wrote:
> Hi Lin Ming,

Hi Teck,

>
> Thanks for this patch.  I am actually working to backport this patch
> to xen-4.1-testing for self-testing.  I have a question as below about
> one of your code.
>
> On Sun, Mar 18, 2012 at 7:50 PM, Lin Ming <mlin@xxxxxxxxxxxxx> wrote:
>> Implement "rtc_timeoffset" and "localtime" options compatible as xm.
>>
>> rtc_timeoffset is the offset between host time and guest time.
>> localtime means to specify whether the emulted RTC appears as UTC or is
>> offset by the host.
>>
>> Signed-off-by: Lin Ming <mlin@xxxxxxxxxxxxx>
>> ---
>>  tools/libxl/libxl_dom.c     |    3 +++
>>  tools/libxl/libxl_types.idl |    1 +
>>  tools/libxl/xl_cmdimpl.c    |   13 +++++++++++++
>>  tools/libxl/xl_sxp.c        |    1 +
>>  4 files changed, 18 insertions(+), 0 deletions(-)
>>
>> diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
>> index 9b33267..0bdd654 100644
>> --- a/tools/libxl/libxl_dom.c
>> +++ b/tools/libxl/libxl_dom.c
>> @@ -91,6 +91,9 @@ int libxl__build_pre(libxl__gc *gc, uint32_t domid,
>>     if (libxl_defbool_val(info->disable_migrate))
>>         xc_domain_disable_migrate(ctx->xch, domid);
>>
>> +    if (info->rtc_timeoffset)
>> +        xc_domain_set_time_offset(ctx->xch, domid, info->rtc_timeoffset);
>> +
>>     if (info->type == LIBXL_DOMAIN_TYPE_HVM) {
>>         unsigned long shadow;
>>         shadow = (info->shadow_memkb + 1023) / 1024;
>> diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
>> index 413a1a6..56f760c 100644
>> --- a/tools/libxl/libxl_types.idl
>> +++ b/tools/libxl/libxl_types.idl
>> @@ -238,6 +238,7 @@ libxl_domain_build_info = Struct("domain_build_info",[
>>     ("target_memkb",    MemKB),
>>     ("video_memkb",     MemKB),
>>     ("shadow_memkb",    MemKB),
>> +    ("rtc_timeoffset",  uint32),
>>     ("disable_migrate", libxl_defbool),
>>     ("cpuid",           libxl_cpuid_policy_list),
>>
>> diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
>> index 1d59b89..b080a2b 100644
>> --- a/tools/libxl/xl_cmdimpl.c
>> +++ b/tools/libxl/xl_cmdimpl.c
>> @@ -697,6 +697,19 @@ static void parse_config_data(const char 
>> *configfile_filename_report,
>>         }
>>     }
>>
>> +    if (!xlu_cfg_get_long(config, "rtc_timeoffset", &l, 0))
>> +        b_info->rtc_timeoffset = l;
>> +
>> +    if (!xlu_cfg_get_long(config, "localtime", &l, 0) && l) {
>> +        time_t t;
>> +        struct tm *tm;
>> +
>> +        t = time(NULL);
>> +        tm = localtime(&t);
>> +
>> +        b_info->rtc_timeoffset -= tm->tm_gmtoff;
>
> If tm->tm_gmtoff is 28800 for example (GMT +8) tested with
> Asia/Singapore and Asia/Hong_Kong, then what is the
> b_info->rct_timeoffset?
> Is it b_info->rtc_timeoffset = b_info->rtc_timeoffset - tm->tm_gmtoff?
>  If this is so, then I guess it is not right.  Shouldn't this be as
> below instead?
>
> b_info->rtc_timeoffset += tm->tm_gmtoff;

You are right.

Python time.altzone/timezone is the offset in seconds "west" of UTC,
while tm->tm_gmtoff is "east" of UTC.

I just realized another problem: does ->tm_gmtoff  already check
DST(day light saving) zone?

Will check.

Thanks,
Lin Ming

>
> In python, time.altzone and time.timezone will return the offset with
> negative for Asia or non-US/most of Western Europe depending it is
> time.altzone or time.timezone according to
> http://docs.python.org/library/time.html... someone correct me if I am
> wrong :p
>
> Tested with python in Scientific Linux 6:
>
> Python 2.6.6 (r266:84292, Jan  4 2012, 16:09:22)
> [GCC 4.4.6 20110731 (Red Hat 4.4.6-3)] on linux2
> Type "help", "copyright", "credits" or "license" for more information.
>>>> import time
>>>> print time.altzone
> -28800
>>>> print time.timezone
> -28800
>>>> print time.tzname
> ('SGT', 'SGT')
>
>
> So unless tm->tm_gmtoff return the same value including negative as
> python time function, then I am totally wrong and sorry about it.
>
> Thanks.
>
> Kindest regards,
> Giam Teck Choon
>
>
>> +    }
>> +
>>     if (!xlu_cfg_get_long (config, "videoram", &l, 0))
>>         b_info->video_memkb = l * 1024;
>>
>> diff --git a/tools/libxl/xl_sxp.c b/tools/libxl/xl_sxp.c
>> index c68b6df..bb1f3da 100644
>> --- a/tools/libxl/xl_sxp.c
>> +++ b/tools/libxl/xl_sxp.c
>> @@ -92,6 +92,7 @@ void printf_info_sexp(int domid, libxl_domain_config 
>> *d_config)
>>         printf("\t\t\t(firmware %s)\n", b_info->u.hvm.firmware);
>>         printf("\t\t\t(video_memkb %"PRId64")\n", b_info->video_memkb);
>>         printf("\t\t\t(shadow_memkb %"PRId64")\n", b_info->shadow_memkb);
>> +        printf("\t\t\t(rtc_timeoffset %"PRId32")\n", 
>> b_info->rtc_timeoffset);
>>         printf("\t\t\t(pae %s)\n", 
>> libxl_defbool_to_string(b_info->u.hvm.pae));
>>         printf("\t\t\t(apic %s)\n",
>>                libxl_defbool_to_string(b_info->u.hvm.apic));
>> --
>> 1.7.2.5
>>
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxx
>> http://lists.xen.org/xen-devel
>
> _______________________________________________
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