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

[Cornelia Huck <cohuck@redhat.com>]

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?