From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:41179) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UFsEu-0007jH-2d for qemu-devel@nongnu.org; Wed, 13 Mar 2013 16:25:33 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UFsEo-0000E6-RZ for qemu-devel@nongnu.org; Wed, 13 Mar 2013 16:25:31 -0400 Received: from mail-ye0-f180.google.com ([209.85.213.180]:41657) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UFsEo-0000E1-Kh for qemu-devel@nongnu.org; Wed, 13 Mar 2013 16:25:26 -0400 Received: by mail-ye0-f180.google.com with SMTP id m14so249284yen.39 for ; Wed, 13 Mar 2013 13:25:26 -0700 (PDT) Sender: fluxion Date: Wed, 13 Mar 2013 15:21:44 -0500 From: mdroth Message-ID: <20130313202144.GF4005@vm> References: <1363169431-1561-1-git-send-email-lilei@linux.vnet.ibm.com> <1363169431-1561-2-git-send-email-lilei@linux.vnet.ibm.com> <20130313200752.GE4005@vm> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130313200752.GE4005@vm> Subject: Re: [Qemu-devel] [PATCH 1/2] qga: add windows implementation for guest-get-time List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: lilei@linux.vnet.ibm.com Cc: aliguori@us.ibm.com, qemu-devel@nongnu.org On Wed, Mar 13, 2013 at 03:07:52PM -0500, mdroth wrote: > On Wed, Mar 13, 2013 at 06:10:30PM +0800, lilei@linux.vnet.ibm.com wrote: > > From: Lei Li > > > > Signed-off-by: Lei Li > > --- > > qga/commands-win32.c | 32 ++++++++++++++++++++++++++++++++ > > 1 files changed, 32 insertions(+), 0 deletions(-) > > > > diff --git a/qga/commands-win32.c b/qga/commands-win32.c > > index 7e8ecb3..0a2bb34 100644 > > --- a/qga/commands-win32.c > > +++ b/qga/commands-win32.c > > @@ -22,6 +22,12 @@ > > #define SHTDN_REASON_FLAG_PLANNED 0x80000000 > > #endif > > > > +/* multiple of 100 nanoseconds elapsed between windows baseline > > + (1/1/1601) and Unix Epoch (1/1/1970), accounting for leap years */ > > +#define W32_FT_OFFSET (10000000ULL * 60 * 60 * 24 * \ > > + (365 * (1970 - 1601) + \ > > + (1970 - 1601) / 4 - 3)) > > + > > static void acquire_privilege(const char *name, Error **err) > > { > > HANDLE token; > > @@ -108,6 +114,32 @@ void qmp_guest_shutdown(bool has_mode, const char *mode, Error **err) > > } > > } > > > > +int64_t qmp_guest_get_time(Error **errp) > > +{ > > + SYSTEMTIME *ts = g_malloc0(sizeof(SYSTEMTIME)); > > Don't we need to free this at some point? Actually, do we even need malloc? Can't be just allocate SYSTEMTIME struct on the stack and pass a pointer to GetSystemTime? > > > + int64_t time_ns; > > + union { > > + UINT64 ns100; > > + FILETIME tf; > > + } time; > > + > > + GetSystemTime(ts); > > + if (!ts) { > > + slog("guest-get-time failed: %d", GetLastError()); > > GetSystemTime() does not seem to set an error that can be retrieved by > GetLastError(). > > > + error_setg_errno(errp, errno, "Failed to get time"); > > + return -1; > > + } > > + > > + if (!SystemTimeToFileTime(ts, &time.tf)) { > > + error_setg_errno(errp, errno, "Failed to convert system time"); > > + return -1; > > + } > > + > > + time_ns = (int64_t)((time.ns100 - W32_FT_OFFSET) * 100); > > I'm not sure how safe this union stuff is. The documentation suggests that in > some circumstances the low/high fields in FILETIME might be padded for > 64-bit alignment and that doing this type of cast could generate an > alignment fault: > > http://msdn.microsoft.com/en-us/library/windows/desktop/ms724284(v=vs.85).aspx > > or it might, perhaps even worse, just silently report the wrong time. > > I think we should just do the math explicitly: > > (((tf.dwHighDateTime << 32) | tf.dwLowDateTime) - W32_FT_OFFSET) * 100) > > (or something along that line) > > > + > > + return time_ns; > > +} > > + > > int64_t qmp_guest_file_open(const char *path, bool has_mode, const char *mode, Error **err) > > { > > error_set(err, QERR_UNSUPPORTED); > > -- > > 1.7.7.6 > >