Re: [Qemu-devel] [PATCH 2/2] qga: add windows implementation for guest-set-time

[Lei Li]

On 03/06/2013 11:05 PM, Eric Blake wrote:
> On 03/06/2013 06:45 AM, Lei Li wrote:
> > Signed-off-by: Lei Li <address@hidden>
> > ---
> >   qga/commands-win32.c |   35 +++++++++++++++++++++++++++++++++++
> >   1 files changed, 35 insertions(+), 0 deletions(-)
> >
> > diff --git a/qga/commands-win32.c b/qga/commands-win32.c
> > index 4febec7..1a90aa7 100644
> > --- a/qga/commands-win32.c
> > +++ b/qga/commands-win32.c
> > @@ -136,6 +136,41 @@ int64_t qmp_guest_get_time(Error **errp)
> >      return time_ns;
> >   }
> >   
> > +void qmp_guest_set_time(int64_t time_ns, Error **errp)
> > +{
> > +    SYSTEMTIME ts;
> > +    FILETIME tf;
> > +    LONGLONG time;
> > +
> > +    /* year-2038 will overflow in case time_t is 32bit */
> > +    if (time_ns / 1000000000 != (time_t)(time_ns / 1000000000)) {
> > +        error_setg(errp, "Time %" PRId64 " is too large", time_ns);
> > +        return;
> > +    }
> Do you really need this?  That is, don't you already know what size
> time_t is on windows; not to mention that on Windows, you aren't going
> through time_t, but directly to tf.dwHighDateTime.

You are right.

> > +
> > +    acquire_privilege(SE_SYSTEMTIME_NAME, errp);
> > +    if (error_is_set(errp)) {
> > +        error_setg(errp, "Failed to acquire privilege");
> > +        return;
> > +    }
> > +
> > +    time = time_ns / 100 + _W32_FT_OFFSET;
> On the other hand, _this_ operation can overflow, so you should be
> checking that time_ns doesn't result in an unexpected time value.

OK.

> > +
> > +    tf.dwLowDateTime = (DWORD) time;
> > +    tf.dwHighDateTime = (DWORD) (time >> 32);
> > +
> > +    if (!FileTimeToSystemTime(&tf, &ts)) {
> > +        error_setg(errp, "Failed to convert system time");
> > +        return;
> > +    }
> > +
> > +    if (!SetSystemTime(&ts)) {
> > +        slog("guest-set-time failed: %d", GetLastError());
> > +        error_setg_errno(errp, errno, "Failed to set time to guest");
> > +        return;
> > +    }
> Trailing whitespace.  Run your submission through scripts/checkpatch.pl.

Yes.

> Should you relinquish the SE_SYSTEMTIME_NAME privilege when exiting this
> function, instead of leaving it always enabled for the remaining life of
> the agent service?

According to the remarks on msdn, this SetSystemTime function will
disables the SE_SYSTEMTIME_NAME privilege before returning.



--
Lei