Re: [libvirt] [PATCH v3] qga: fence guest-set-time if hwclock not available
On 12/5/19 2:12 PM, Cornelia Huck wrote:
On Thu, 5 Dec 2019 14:05:19 +0100
Philippe Mathieu-Daudé <philmd(a)redhat.com> wrote:
> Hi Cornelia,
>
> On 12/5/19 12:53 PM, Cornelia Huck wrote:
>> The Posix implementation of guest-set-time invokes hwclock to
>> set/retrieve the time to/from the hardware clock. If hwclock
>> is not available, the user is currently informed that "hwclock
>> failed to set hardware clock to system time", which is quite
>> misleading. This may happen e.g. on s390x, which has a different
>> timekeeping concept anyway.
>>
>> Let's check for the availability of the hwclock command and
>> return QERR_UNSUPPORTED for guest-set-time if it is not available.
>>
>> Reviewed-by: Laszlo Ersek <lersek(a)redhat.com>
>> Reviewed-by: Daniel P. Berrangé <berrange(a)redhat.com>
>> Reviewed-by: Michael Roth <mdroth(a)linux.vnet.ibm.com>
>> Signed-off-by: Cornelia Huck <cohuck(a)redhat.com>
>> ---
>>
>> v2->v3:
>> - added 'static' keyword to hwclock_path
>>
>> Not sure what tree this is going through; if there's no better place,
>> I can also take this through the s390 tree.
>
> s390 or trivial trees seems appropriate.
>
>>
>> ---
>> qga/commands-posix.c | 13 ++++++++++++-
>> 1 file changed, 12 insertions(+), 1 deletion(-)
>>
>> diff --git a/qga/commands-posix.c b/qga/commands-posix.c
>> index 1c1a165daed8..0be301a4ea77 100644
>> --- a/qga/commands-posix.c
>> +++ b/qga/commands-posix.c
>> @@ -156,6 +156,17 @@ void qmp_guest_set_time(bool has_time, int64_t time_ns,
Error **errp)
>> pid_t pid;
>> Error *local_err = NULL;
>> struct timeval tv;
>> + static const char hwclock_path[] = "/sbin/hwclock";
>> + static int hwclock_available = -1;
>> +
>> + if (hwclock_available < 0) {
>> + hwclock_available = (access(hwclock_path, X_OK) == 0);
>> + }
>> +
>> + if (!hwclock_available) {
>> + error_setg(errp, QERR_UNSUPPORTED);
>
> In include/qapi/qmp/qerror.h we have:
>
> /*
> * These macros will go away, please don't use in new code, and do not
> * add new ones!
> */
Sigh, it is really hard to keep track here :( I just copied from other
callers in this file...
>
> Maybe we can replace it by "this feature is not supported on this
> architecture"? (or without 'on this architecture').
This is not really architecture specific, you'd get this on any setup
that does not have /sbin/hwclock.
Q: Is libvirt doing anything with such an error message from QEMU? Do
we have the freedom to say e.g "guest-set-time is not supported" or so?
Or is it beneficial to print the same error message for any unsupported
feature?
Cc'ing Markus who added the command and libvir-list.
Using "guest-set-time is not supported" or "this command is not
supported":
Reviewed-by: Philippe Mathieu-Daudé <philmd(a)redhat.com>
>> + return;
>> + }
>>
>> /* If user has passed a time, validate and set it. */
>> if (has_time) {
>> @@ -195,7 +206,7 @@ void qmp_guest_set_time(bool has_time, int64_t time_ns, Error
**errp)
>>
>> /* Use '/sbin/hwclock -w' to set RTC from the system time,
>> * or '/sbin/hwclock -s' to set the system time from RTC. */
>> - execle("/sbin/hwclock", "hwclock", has_time ?
"-w" : "-s",
>> + execle(hwclock_path, "hwclock", has_time ? "-w" :
"-s",
>> NULL, environ);
>> _exit(EXIT_FAILURE);
>> } else if (pid < 0) {
>>
>