[Qemu-devel] [PATCH 0/2 v4] Time resync support by qemu-ga

[Qemu-devel] [PATCH 0/2 v4] Time resync support by qemu-ga

[Lei Li]

This patch series attempts to add time resync support
to qemu-ga by introducing qemu-ga commands guest-get-time
and guest-set-time.

Right now, when a guest is paused or migrated to a file
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.
So adding new guest-agent command that is called any time
a guest is resumed  and which tells the guest to update its
own wall clock time based on the information from the host
will make it easier for a guest to resynchronize without
waiting for NTP.

The previous RFC send for discussion and suggestion as link
here:

http://article.gmane.org/gmane.comp.emulators.qemu/186126

The interface for these commands like:

{ 'command': 'guest-get-time', 'returns': 'int' }

{ 'command': 'guest-set-time', 'data': { 'time': int } }

Notes:
For the implementition of win32-specific commands, I plan
to send it out in another thread later.

Suggestions and comments are welcome!

Changes since v3:
  - Doc improvement based on Eric's suggestions.
  - Overflow check improve from Eric. 

Changes since v2:
  - Get rid of utc-offset, and make it just pass single nanoseconds
    relative to the Epoch in UTC/GMT according to Anthony and
    Eric's comments.
  - Make time argument mandatory.
  - Fix the overflow check for year-2038 problem.
  - Error handel improvment from Eric. 

Changes since v1:
  - Squashed patches add support to get host time and add
    guest-get-time command into one.
  - Documents improvment based on the suggestions from
    Eric and Mike.
  - Change the name of 'HostTimeInfo' to 'TimeInfo'.
  - Better use-case and logic for 'guest-set-time'
    command suggested by Eric.
  - Error handel improvment from Luiz.

Lei Li (2):
  qga: add guest-get-time command
  qga: add guest-set-time command

[Qemu-devel] [PATCH 1/2] qga: add guest-get-time command

[Lei Li]

Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
---
 qga/commands-posix.c | 16 ++++++++++++++++
 qga/qapi-schema.json | 13 +++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index 0ad73f3..6fc6003 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -119,6 +119,22 @@ void qmp_guest_shutdown(bool has_mode, const char *mode, Error **err)
     /* succeded */
 }
 
+int64_t qmp_guest_get_time(Error **errp)
+{
+   int ret;
+   qemu_timeval tq;
+   int64_t time_ns;
+
+   ret = qemu_gettimeofday(&tq);
+   if (ret < 0) {
+       error_setg_errno(errp, errno, "Failed to get time");
+       return -1;
+   }
+
+   time_ns = tq.tv_sec * 1000000000LL + tq.tv_usec * 1000;
+   return time_ns;
+}
+
 typedef struct GuestFileHandle {
     uint64_t id;
     FILE *fh;
diff --git a/qga/qapi-schema.json b/qga/qapi-schema.json
index d91d903..52bb091 100644
--- a/qga/qapi-schema.json
+++ b/qga/qapi-schema.json
@@ -83,6 +83,19 @@
 { 'command': 'guest-ping' }
 
 ##
+# @guest-get-time:
+#
+# Get the information about guest time relative to the Epoch
+# of 1970-01-01 in UTC.
+#
+# Returns: Time in nanoseconds on success.
+#
+# Since 1.5
+##
+{ 'command': 'guest-get-time',
+  'returns': 'int' }
+
+##
 # @GuestAgentCommandInfo:
 #
 # Information about guest agent commands.
-- 
1.7.11.7

Re: [Qemu-devel] [PATCH 1/2] qga: add guest-get-time command

[mdroth]

On Mon, Mar 04, 2013 at 05:16:29PM +0800, Lei Li wrote:
> Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>

Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>

> ---
>  qga/commands-posix.c | 16 ++++++++++++++++
>  qga/qapi-schema.json | 13 +++++++++++++
>  2 files changed, 29 insertions(+)
> 
> diff --git a/qga/commands-posix.c b/qga/commands-posix.c
> index 0ad73f3..6fc6003 100644
> --- a/qga/commands-posix.c
> +++ b/qga/commands-posix.c
> @@ -119,6 +119,22 @@ void qmp_guest_shutdown(bool has_mode, const char *mode, Error **err)
>      /* succeded */
>  }
> 
> +int64_t qmp_guest_get_time(Error **errp)
> +{
> +   int ret;
> +   qemu_timeval tq;
> +   int64_t time_ns;
> +
> +   ret = qemu_gettimeofday(&tq);
> +   if (ret < 0) {
> +       error_setg_errno(errp, errno, "Failed to get time");
> +       return -1;
> +   }
> +
> +   time_ns = tq.tv_sec * 1000000000LL + tq.tv_usec * 1000;
> +   return time_ns;
> +}
> +
>  typedef struct GuestFileHandle {
>      uint64_t id;
>      FILE *fh;
> diff --git a/qga/qapi-schema.json b/qga/qapi-schema.json
> index d91d903..52bb091 100644
> --- a/qga/qapi-schema.json
> +++ b/qga/qapi-schema.json
> @@ -83,6 +83,19 @@
>  { 'command': 'guest-ping' }
> 
>  ##
> +# @guest-get-time:
> +#
> +# Get the information about guest time relative to the Epoch
> +# of 1970-01-01 in UTC.
> +#
> +# Returns: Time in nanoseconds on success.
> +#
> +# Since 1.5
> +##
> +{ 'command': 'guest-get-time',
> +  'returns': 'int' }
> +
> +##
>  # @GuestAgentCommandInfo:
>  #
>  # Information about guest agent commands.
> -- 
> 1.7.11.7
> 

Re: [Qemu-devel] [PATCH 1/2] qga: add guest-get-time command

[Eric Blake]

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On 03/04/2013 02:16 AM, Lei Li wrote:
> Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
> ---
>  qga/commands-posix.c | 16 ++++++++++++++++
>  qga/qapi-schema.json | 13 +++++++++++++
>  2 files changed, 29 insertions(+)
> 

>  ##
> +# @guest-get-time:
> +#
> +# Get the information about guest time relative to the Epoch
> +# of 1970-01-01 in UTC.
> +#
> +# Returns: Time in nanoseconds on success.

The return value is only possible on success in the first place, so you
can simplify this:

s/ on success//

But that's minor, and I'm okay even with the longer wording, so:

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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

[Lei Li]

Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
---
 qga/commands-posix.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 qga/qapi-schema.json | 27 ++++++++++++++++++++++++++
 2 files changed, 81 insertions(+)

diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index 6fc6003..0515f5f 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -135,6 +135,60 @@ 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 (time_ns / 1000000000 != (time_t)(time_ns / 1000000000)) {
+        error_setg(errp, "Time %" PRId64 " is too large", time_ns);
+    }
+
+    tv.tv_sec = time_ns / 1000000000;
+    tv.tv_usec = (time_ns % 1000000000) / 1000;
+
+    ret = settimeofday(&tv, NULL);
+    if (ret < 0) {
+        error_setg_errno(errp, errno, "Failed to set time to guest");
+        return;
+    }
+
+    /* Set the Hardware Clock to the current System Time. */
+    pid = fork();
+    if (pid == 0) {
+        setsid();
+        reopen_fd_to_null(0);
+        reopen_fd_to_null(1);
+        reopen_fd_to_null(2);
+
+        execle("/sbin/hwclock", "hwclock", "-w", NULL, environ);
+        _exit(EXIT_FAILURE);
+    } else if (pid < 0) {
+        error_setg_errno(errp, errno, "failed to create child process");
+        return;
+    }
+
+    ga_wait_child(pid, &status, &local_err);
+    if (error_is_set(&local_err)) {
+        error_propagate(errp, local_err);
+        return;
+    }
+
+    if (!WIFEXITED(status)) {
+        error_setg(errp, "child process has terminated abnormally");
+        return;
+    }
+
+    if (WEXITSTATUS(status)) {
+        error_setg(errp, "hwclock failed to set hardware clock to system time");
+        return;
+    }
+}
+
 typedef struct GuestFileHandle {
     uint64_t id;
     FILE *fh;
diff --git a/qga/qapi-schema.json b/qga/qapi-schema.json
index 52bb091..ce964e9 100644
--- a/qga/qapi-schema.json
+++ b/qga/qapi-schema.json
@@ -96,6 +96,33 @@
   'returns': 'int' }
 
 ##
+# @guest-set-time:
+#
+# Set guest time.
+#
+# When a guest is paused or migrated to a file 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.
+#
+# Returns: Nothing on success.
+#
+# Since: 1.5
+##
+{ 'command': 'guest-set-time',
+  'data': { 'time': 'int' } }
+
+##
 # @GuestAgentCommandInfo:
 #
 # Information about guest agent commands.
-- 
1.7.11.7

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

[mdroth]

On Mon, Mar 04, 2013 at 05:16:30PM +0800, Lei Li wrote:
> Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
> ---
>  qga/commands-posix.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  qga/qapi-schema.json | 27 ++++++++++++++++++++++++++
>  2 files changed, 81 insertions(+)
> 
> diff --git a/qga/commands-posix.c b/qga/commands-posix.c
> index 6fc6003..0515f5f 100644
> --- a/qga/commands-posix.c
> +++ b/qga/commands-posix.c
> @@ -135,6 +135,60 @@ 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 (time_ns / 1000000000 != (time_t)(time_ns / 1000000000)) {
> +        error_setg(errp, "Time %" PRId64 " is too large", time_ns);
> +    }
> +
> +    tv.tv_sec = time_ns / 1000000000;
> +    tv.tv_usec = (time_ns % 1000000000) / 1000;
> +
> +    ret = settimeofday(&tv, NULL);
> +    if (ret < 0) {
> +        error_setg_errno(errp, errno, "Failed to set time to guest");
> +        return;
> +    }
> +
> +    /* Set the Hardware Clock to the current System Time. */
> +    pid = fork();
> +    if (pid == 0) {
> +        setsid();
> +        reopen_fd_to_null(0);
> +        reopen_fd_to_null(1);
> +        reopen_fd_to_null(2);
> +
> +        execle("/sbin/hwclock", "hwclock", "-w", NULL, environ);
> +        _exit(EXIT_FAILURE);
> +    } else if (pid < 0) {
> +        error_setg_errno(errp, errno, "failed to create child process");
> +        return;
> +    }
> +
> +    ga_wait_child(pid, &status, &local_err);
> +    if (error_is_set(&local_err)) {
> +        error_propagate(errp, local_err);
> +        return;
> +    }
> +
> +    if (!WIFEXITED(status)) {
> +        error_setg(errp, "child process has terminated abnormally");
> +        return;
> +    }
> +
> +    if (WEXITSTATUS(status)) {
> +        error_setg(errp, "hwclock failed to set hardware clock to system time");
> +        return;
> +    }
> +}
> +
>  typedef struct GuestFileHandle {
>      uint64_t id;
>      FILE *fh;
> diff --git a/qga/qapi-schema.json b/qga/qapi-schema.json
> index 52bb091..ce964e9 100644
> --- a/qga/qapi-schema.json
> +++ b/qga/qapi-schema.json
> @@ -96,6 +96,33 @@
>    'returns': 'int' }
> 
>  ##
> +# @guest-set-time:
> +#
> +# Set guest time.
> +#
> +# When a guest is paused or migrated to a file 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

"time in nanoseconds", but I can fix this up myself if there are no
other comments that need to be addressed.

Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>

> +#        1970-01-01 in UTC.
> +#
> +# Returns: Nothing on success.
> +#
> +# Since: 1.5
> +##
> +{ 'command': 'guest-set-time',
> +  'data': { 'time': 'int' } }
> +
> +##
>  # @GuestAgentCommandInfo:
>  #
>  # Information about guest agent commands.
> -- 
> 1.7.11.7
> 

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

[Eric Blake]

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On 03/04/2013 11:16 AM, mdroth wrote:
> On Mon, Mar 04, 2013 at 05:16:30PM +0800, Lei Li wrote:
>> Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
>> ---
>>  qga/commands-posix.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>>  qga/qapi-schema.json | 27 ++++++++++++++++++++++++++
>>  2 files changed, 81 insertions(+)

>>
>> +# @time: time of nanoseconds, relative to the Epoch of
> 
> "time in nanoseconds", but I can fix this up myself if there are no
> other comments that need to be addressed.

Unfortunately, that's not the only problem, and I think a v5 is
warranted (see my other mail).

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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

[Eric Blake]

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On 03/04/2013 02:16 AM, Lei Li wrote:
> Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
> ---
>  qga/commands-posix.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  qga/qapi-schema.json | 27 ++++++++++++++++++++++++++
>  2 files changed, 81 insertions(+)
> 
> diff --git a/qga/commands-posix.c b/qga/commands-posix.c
> index 6fc6003..0515f5f 100644
> --- a/qga/commands-posix.c
> +++ b/qga/commands-posix.c
> @@ -135,6 +135,60 @@ 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 (time_ns / 1000000000 != (time_t)(time_ns / 1000000000)) {
> +        error_setg(errp, "Time %" PRId64 " is too large", time_ns);

You set the error, but then fall through...

> +    }
> +
> +    tv.tv_sec = time_ns / 1000000000;
> +    tv.tv_usec = (time_ns % 1000000000) / 1000;
> +
> +    ret = settimeofday(&tv, NULL);

...and change the guest time to an invalid value anyways.  This could
cause the guest to severely misbehave.

> +    if (ret < 0) {
> +        error_setg_errno(errp, errno, "Failed to set time to guest");
> +        return;

You should have done an early exit on the other error, like you did here.

> +#
> +# This command tries to set guest time based on the information
> +# from host or an absolute value given by management app, and

The absolute value given by the management app _is_ information from the
host.  I'd simplify this to just:

This command tries to set guest time to the given value, then

> +# set the Hardware Clock to the current System Time. This

s/set/sets/

> +# 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.
> +#

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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