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Re: [Qemu-devel] [PATCH 2/2] qga: add guest-set-time command


From: Lei Li
Subject: Re: [Qemu-devel] [PATCH 2/2] qga: add guest-set-time command
Date: Mon, 04 Mar 2013 16:25:48 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0

On 03/02/2013 01:38 AM, Eric Blake wrote:
On 03/01/2013 02:33 AM, Lei Li wrote:
Signed-off-by: Lei Li <address@hidden>
---
  qga/commands-posix.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++
  qga/qapi-schema.json | 27 ++++++++++++++++++++++++++
  2 files changed, 82 insertions(+)

diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index f159e25..e246a0d 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -135,6 +135,61 @@ int64_t qmp_guest_get_time(Error **errp)
     return time_ns;
  }
+void qmp_guest_set_time(int64_t time_ns, Error **errp)
+{
+    int ret;
+    int status;
+    pid_t pid;
+    Error *local_err = NULL;
+    struct timeval tv;
+
+    /* year-2038 will overflow in case time_t is 32bit */
+    if ((sizeof(time_t) <= 4) && ((unsigned long) time_ns & (1ul << 31))) {
Wrong.  If 'unsigned long' and 'time_t' are both 32 bits, but time_ns is
0x1000000000000000, then the cast truncates to 0 and you don't report
overflow.  Conversely, if time_ns is 0x80000000, you report overflow,
even though this value fits in 32-bit time_t after you do division from
nanoseconds back to seconds.  What you WANT is:

Yes, you are right.. thanks.


if (time_ns / 1000000000 != (time_t)(time_ns / 1000000000)) {

+        error_setg_errno(errp, errno, "Invalid time %ld for overflow",
+                         time_ns);
That wording sounds awkward.  Worse, errno is NOT set to anything sane,
so you do NOT want error_setg_errno.  And %ld is wrong for int64_t on
32-bit platforms.  How about:

error_setg(errp, "Time %" PRI64D " is too large", time_ns);

Sure, will address it as the your later reply.

+++ b/qga/qapi-schema.json
@@ -99,6 +99,33 @@
    'returns': 'int' }
##
+# @guest-set-time:
+#
+# Set guest time.
+#
+# Right now, when a guest is paused or migrated to a file
s/Right now, when/When/

+# then loaded from that file, the guest OS has no idea that
+# there was a big gap in the time. Depending on how long
+# the gap was, NTP might not be able to resynchronize the
+# guest.
+#
+# This command tries to set guest time based on the information
+# from host or an absolute value given by management app, and
+# set the Hardware Clock to the current System Time. This
+# will make it easier for a guest to resynchronize without
+# waiting for NTP.
+#
+# @time: time of nanoseconds, relative to the Epoch of
+#        1970-01-01 in UTC/GMT.
drop '/GMT'

+#
+# Returns: Nothing on success.
+#
+# Since: 1.5
+##
+{ 'command': 'guest-set-time',
+  'data': { 'time': 'int' } }
+
+##
  # @GuestAgentCommandInfo:
  #
  # Information about guest agent commands.



--
Lei




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