Re: [PATCH v3] qga: fence guest-set-time if hwclock not available

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 12/9/19 7:33 PM, Cornelia Huck wrote:
> On Fri, 06 Dec 2019 08:17:27 +0100
> Markus Armbruster <armbru@redhat.com> wrote:
> 
>> Cornelia Huck <cohuck@redhat.com> writes:
>>
>>> On Thu, 5 Dec 2019 14:05:19 +0100
>>> Philippe Mathieu-Daudé <philmd@redhat.com> wrote:
>>>   
>>>> Hi Cornelia,
>>>>
>>>> On 12/5/19 12:53 PM, Cornelia Huck wrote:
>>>>> The Posix implementation of guest-set-time invokes hwclock to
>>>>> set/retrieve the time to/from the hardware clock. If hwclock
>>>>> is not available, the user is currently informed that "hwclock
>>>>> failed to set hardware clock to system time", which is quite
>>>>> misleading. This may happen e.g. on s390x, which has a different
>>>>> timekeeping concept anyway.
>>>>>
>>>>> Let's check for the availability of the hwclock command and
>>>>> return QERR_UNSUPPORTED for guest-set-time if it is not available.
>>>>>
>>>>> Reviewed-by: Laszlo Ersek <lersek@redhat.com>
>>>>> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
>>>>> Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
>>>>> Signed-off-by: Cornelia Huck <cohuck@redhat.com>
>>>>> ---
>>>>>
>>>>> v2->v3:
>>>>>     - added 'static' keyword to hwclock_path
>>>>>
>>>>> Not sure what tree this is going through; if there's no better place,
>>>>> I can also take this through the s390 tree.
>>>>
>>>> s390 or trivial trees seems appropriate.
>>>>    
>>>>>
>>>>> ---
>>>>>    qga/commands-posix.c | 13 ++++++++++++-
>>>>>    1 file changed, 12 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/qga/commands-posix.c b/qga/commands-posix.c
>>>>> index 1c1a165daed8..0be301a4ea77 100644
>>>>> --- a/qga/commands-posix.c
>>>>> +++ b/qga/commands-posix.c
>>>>> @@ -156,6 +156,17 @@ void qmp_guest_set_time(bool has_time, int64_t time_ns, Error **errp)
>>>>>        pid_t pid;
>>>>>        Error *local_err = NULL;
>>>>>        struct timeval tv;
>>>>> +    static const char hwclock_path[] = "/sbin/hwclock";
>>>>> +    static int hwclock_available = -1;
>>>>> +
>>>>> +    if (hwclock_available < 0) {
>>>>> +        hwclock_available = (access(hwclock_path, X_OK) == 0);
>>>>> +    }
>>>>> +
>>>>> +    if (!hwclock_available) {
>>>>> +        error_setg(errp, QERR_UNSUPPORTED);
>>>>
>>>> In include/qapi/qmp/qerror.h we have:
>>>>
>>>> /*
>>>>    * These macros will go away, please don't use in new code, and do not
>>>>    * add new ones!
>>>>    */
>>>
>>> Sigh, it is really hard to keep track here :( I just copied from other
>>> callers in this file...
>>
>> I'm not faulting you for that.
>>
>> I think this new use is acceptable.  For details, see my other reply in
>> this thread.
> 
> Ok, thanks for your explanation there.
> 
> I guess I'll queue this on s390-next... Philippe, any objections to
> adding your R-b to the unmodified patch?

Certainly, sorry for the delay/noise on this trivial patch, I learned 
the subtle differences between comments in code and reality :)

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>