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Re: [Qemu-devel] [PATCH 2/2] qga: add guest-set-time command
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH 2/2] qga: add guest-set-time command |
Date: |
Fri, 01 Mar 2013 10:38:10 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130219 Thunderbird/17.0.3 |
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:
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);
> +++ 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.
>
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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