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

[Markus Armbruster <armbru@redhat.com>]

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.

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