[v1] qga: fence guest-set-time if hwclock not available

[PATCH RFC] qga: fence guest-set-time if hwclock not available

Posted by Cornelia Huck 4 years, 5 months ago

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.

Signed-off-by: Cornelia Huck <cohuck@redhat.com>
---

Not sure if that is the correct approach, but the current error
message is really quite confusing.

Gave it a quick test with an s390x and an x86_64 guest; invoking
'virsh domtime <value>' now fails with 'not currently supported'
on s390x and continues to work as before on x86_64.

---
 qga/commands-posix.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index 1c1a165daed8..bd298a38b716 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -149,6 +149,13 @@ int64_t qmp_guest_get_time(Error **errp)
    return tq.tv_sec * 1000000000LL + tq.tv_usec * 1000;
 }
 
+static int check_hwclock_available(const char *path)
+{
+    struct stat st;
+
+    return (stat(path, &st) < 0) ? 0 : 1;
+}
+
 void qmp_guest_set_time(bool has_time, int64_t time_ns, Error **errp)
 {
     int ret;
@@ -156,6 +163,17 @@ void qmp_guest_set_time(bool has_time, int64_t time_ns, Error **errp)
     pid_t pid;
     Error *local_err = NULL;
     struct timeval tv;
+    const char *hwclock_path = "/sbin/hwclock";
+    static int hwclock_available = -1;
+
+    if (hwclock_available < 0) {
+        hwclock_available = check_hwclock_available(hwclock_path);
+    }
+
+    if (!hwclock_available) {
+        error_setg(errp, QERR_UNSUPPORTED);
+        return;
+    }
 
     /* If user has passed a time, validate and set it. */
     if (has_time) {
@@ -195,7 +213,7 @@ 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) {
-- 
2.21.0

Re: [PATCH RFC] qga: fence guest-set-time if hwclock not available

Posted by Daniel P. Berrangé 4 years, 5 months ago

On Thu, Nov 28, 2019 at 01:36:58PM +0100, 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.
> 
> Signed-off-by: Cornelia Huck <cohuck@redhat.com>
> ---
> 
> Not sure if that is the correct approach, but the current error
> message is really quite confusing.

I guess the alternative is to just #ifndef __s390x__ the whole
impl of the qmp_guest_set_time  method, but I don't have a
strong opinion on which is best.

> 
> Gave it a quick test with an s390x and an x86_64 guest; invoking
> 'virsh domtime <value>' now fails with 'not currently supported'
> on s390x and continues to work as before on x86_64.
> 
> ---
>  qga/commands-posix.c | 20 +++++++++++++++++++-
>  1 file changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/qga/commands-posix.c b/qga/commands-posix.c
> index 1c1a165daed8..bd298a38b716 100644
> --- a/qga/commands-posix.c
> +++ b/qga/commands-posix.c
> @@ -149,6 +149,13 @@ int64_t qmp_guest_get_time(Error **errp)
>     return tq.tv_sec * 1000000000LL + tq.tv_usec * 1000;
>  }
>  
> +static int check_hwclock_available(const char *path)
> +{
> +    struct stat st;
> +
> +    return (stat(path, &st) < 0) ? 0 : 1;
> +}
> +
>  void qmp_guest_set_time(bool has_time, int64_t time_ns, Error **errp)
>  {
>      int ret;
> @@ -156,6 +163,17 @@ void qmp_guest_set_time(bool has_time, int64_t time_ns, Error **errp)
>      pid_t pid;
>      Error *local_err = NULL;
>      struct timeval tv;
> +    const char *hwclock_path = "/sbin/hwclock";
> +    static int hwclock_available = -1;
> +
> +    if (hwclock_available < 0) {
> +        hwclock_available = check_hwclock_available(hwclock_path);

Could do this inline with:

    hwclock_available = (access(hwclock_available, X_OK) == 0);

getting a slightly better result as this check for it being
executable as well as existing.

> +    }
> +
> +    if (!hwclock_available) {
> +        error_setg(errp, QERR_UNSUPPORTED);
> +        return;
> +    }
>  
>      /* If user has passed a time, validate and set it. */
>      if (has_time) {
> @@ -195,7 +213,7 @@ 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) {
> -- 
> 2.21.0
> 
> 

Regards,
Daniel
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Re: [PATCH RFC] qga: fence guest-set-time if hwclock not available

Posted by Laszlo Ersek 4 years, 5 months ago

On 11/28/19 13:45, Daniel P. Berrangé wrote:
> On Thu, Nov 28, 2019 at 01:36:58PM +0100, 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.
>>
>> Signed-off-by: Cornelia Huck <cohuck@redhat.com>
>> ---
>>
>> Not sure if that is the correct approach, but the current error
>> message is really quite confusing.
> 
> I guess the alternative is to just #ifndef __s390x__ the whole
> impl of the qmp_guest_set_time  method, but I don't have a
> strong opinion on which is best.
> 
>>
>> Gave it a quick test with an s390x and an x86_64 guest; invoking
>> 'virsh domtime <value>' now fails with 'not currently supported'
>> on s390x and continues to work as before on x86_64.
>>
>> ---
>>  qga/commands-posix.c | 20 +++++++++++++++++++-
>>  1 file changed, 19 insertions(+), 1 deletion(-)
>>
>> diff --git a/qga/commands-posix.c b/qga/commands-posix.c
>> index 1c1a165daed8..bd298a38b716 100644
>> --- a/qga/commands-posix.c
>> +++ b/qga/commands-posix.c
>> @@ -149,6 +149,13 @@ int64_t qmp_guest_get_time(Error **errp)
>>     return tq.tv_sec * 1000000000LL + tq.tv_usec * 1000;
>>  }
>>  
>> +static int check_hwclock_available(const char *path)
>> +{
>> +    struct stat st;
>> +
>> +    return (stat(path, &st) < 0) ? 0 : 1;
>> +}
>> +
>>  void qmp_guest_set_time(bool has_time, int64_t time_ns, Error **errp)
>>  {
>>      int ret;
>> @@ -156,6 +163,17 @@ void qmp_guest_set_time(bool has_time, int64_t time_ns, Error **errp)
>>      pid_t pid;
>>      Error *local_err = NULL;
>>      struct timeval tv;
>> +    const char *hwclock_path = "/sbin/hwclock";

slight style / semantics improvement could be

  static const char hwclock_path[] = "/sbin/hwclock";

Thanks
Laszlo

>> +    static int hwclock_available = -1;
>> +
>> +    if (hwclock_available < 0) {
>> +        hwclock_available = check_hwclock_available(hwclock_path);
> 
> Could do this inline with:
> 
>     hwclock_available = (access(hwclock_available, X_OK) == 0);
> 
> getting a slightly better result as this check for it being
> executable as well as existing.
> 
>> +    }
>> +
>> +    if (!hwclock_available) {
>> +        error_setg(errp, QERR_UNSUPPORTED);
>> +        return;
>> +    }
>>  
>>      /* If user has passed a time, validate and set it. */
>>      if (has_time) {
>> @@ -195,7 +213,7 @@ 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) {
>> -- 
>> 2.21.0
>>
>>
> 
> Regards,
> Daniel
>

Re: [PATCH RFC] qga: fence guest-set-time if hwclock not available

Posted by Cornelia Huck 4 years, 5 months ago

On Thu, 28 Nov 2019 12:45:32 +0000
Daniel P. Berrangé <berrange@redhat.com> wrote:

> On Thu, Nov 28, 2019 at 01:36:58PM +0100, 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.
> > 
> > Signed-off-by: Cornelia Huck <cohuck@redhat.com>
> > ---
> > 
> > Not sure if that is the correct approach, but the current error
> > message is really quite confusing.  
> 
> I guess the alternative is to just #ifndef __s390x__ the whole
> impl of the qmp_guest_set_time  method, but I don't have a
> strong opinion on which is best.

This hardcodes this as a s390x specialty, though, and I'm not sure that
assumption is and will stay correct.

> 
> > 
> > Gave it a quick test with an s390x and an x86_64 guest; invoking
> > 'virsh domtime <value>' now fails with 'not currently supported'
> > on s390x and continues to work as before on x86_64.
> > 
> > ---
> >  qga/commands-posix.c | 20 +++++++++++++++++++-
> >  1 file changed, 19 insertions(+), 1 deletion(-)
> > 
> > diff --git a/qga/commands-posix.c b/qga/commands-posix.c
> > index 1c1a165daed8..bd298a38b716 100644
> > --- a/qga/commands-posix.c
> > +++ b/qga/commands-posix.c
> > @@ -149,6 +149,13 @@ int64_t qmp_guest_get_time(Error **errp)
> >     return tq.tv_sec * 1000000000LL + tq.tv_usec * 1000;
> >  }
> >  
> > +static int check_hwclock_available(const char *path)
> > +{
> > +    struct stat st;
> > +
> > +    return (stat(path, &st) < 0) ? 0 : 1;
> > +}
> > +
> >  void qmp_guest_set_time(bool has_time, int64_t time_ns, Error **errp)
> >  {
> >      int ret;
> > @@ -156,6 +163,17 @@ void qmp_guest_set_time(bool has_time, int64_t time_ns, Error **errp)
> >      pid_t pid;
> >      Error *local_err = NULL;
> >      struct timeval tv;
> > +    const char *hwclock_path = "/sbin/hwclock";
> > +    static int hwclock_available = -1;
> > +
> > +    if (hwclock_available < 0) {
> > +        hwclock_available = check_hwclock_available(hwclock_path);  
> 
> Could do this inline with:
> 
>     hwclock_available = (access(hwclock_available, X_OK) == 0);
> 
> getting a slightly better result as this check for it being
> executable as well as existing.

Yes, that looks better. Can do if we agree on this approach.

> 
> > +    }
> > +
> > +    if (!hwclock_available) {
> > +        error_setg(errp, QERR_UNSUPPORTED);
> > +        return;
> > +    }
> >  
> >      /* If user has passed a time, validate and set it. */
> >      if (has_time) {
> > @@ -195,7 +213,7 @@ 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) {
> > -- 
> > 2.21.0
> > 
> >   
> 
> Regards,
> Daniel

Re: [PATCH RFC] qga: fence guest-set-time if hwclock not available

Posted by Daniel P. Berrangé 4 years, 5 months ago

On Thu, Nov 28, 2019 at 01:49:32PM +0100, Cornelia Huck wrote:
> On Thu, 28 Nov 2019 12:45:32 +0000
> Daniel P. Berrangé <berrange@redhat.com> wrote:
> 
> > On Thu, Nov 28, 2019 at 01:36:58PM +0100, 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.
> > > 
> > > Signed-off-by: Cornelia Huck <cohuck@redhat.com>
> > > ---
> > > 
> > > Not sure if that is the correct approach, but the current error
> > > message is really quite confusing.  
> > 
> > I guess the alternative is to just #ifndef __s390x__ the whole
> > impl of the qmp_guest_set_time  method, but I don't have a
> > strong opinion on which is best.
> 
> This hardcodes this as a s390x specialty, though, and I'm not sure that
> assumption is and will stay correct.

> 
> > 
> > > 
> > > Gave it a quick test with an s390x and an x86_64 guest; invoking
> > > 'virsh domtime <value>' now fails with 'not currently supported'
> > > on s390x and continues to work as before on x86_64.
> > > 
> > > ---
> > >  qga/commands-posix.c | 20 +++++++++++++++++++-
> > >  1 file changed, 19 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/qga/commands-posix.c b/qga/commands-posix.c
> > > index 1c1a165daed8..bd298a38b716 100644
> > > --- a/qga/commands-posix.c
> > > +++ b/qga/commands-posix.c
> > > @@ -149,6 +149,13 @@ int64_t qmp_guest_get_time(Error **errp)
> > >     return tq.tv_sec * 1000000000LL + tq.tv_usec * 1000;
> > >  }
> > >  
> > > +static int check_hwclock_available(const char *path)
> > > +{
> > > +    struct stat st;
> > > +
> > > +    return (stat(path, &st) < 0) ? 0 : 1;
> > > +}
> > > +
> > >  void qmp_guest_set_time(bool has_time, int64_t time_ns, Error **errp)
> > >  {
> > >      int ret;
> > > @@ -156,6 +163,17 @@ void qmp_guest_set_time(bool has_time, int64_t time_ns, Error **errp)
> > >      pid_t pid;
> > >      Error *local_err = NULL;
> > >      struct timeval tv;
> > > +    const char *hwclock_path = "/sbin/hwclock";
> > > +    static int hwclock_available = -1;
> > > +
> > > +    if (hwclock_available < 0) {
> > > +        hwclock_available = check_hwclock_available(hwclock_path);  
> > 
> > Could do this inline with:
> > 
> >     hwclock_available = (access(hwclock_available, X_OK) == 0);
> > 
> > getting a slightly better result as this check for it being
> > executable as well as existing.
> 
> Yes, that looks better. Can do if we agree on this approach.

I'm fine with this


Regards,
Daniel
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