Re: [PATCH] xen/passthrough: add missing error-report include

[Markus Armbruster <armbru@redhat.com>]

Daniel P. Berrangé <berrange@redhat.com> writes:

> On Fri, Jul 18, 2025 at 07:59:50AM +0200, Markus Armbruster wrote:
>> Markus Armbruster <armbru@redhat.com> writes:
>> 
>> > Adam Williamson <awilliam@redhat.com> writes:
>> >
>> >> In cfcacba an `error_report` was added to this file, but the
>> >> corresponding include of `qemu/error-report.h` was missed. This
>> >> only becomes apparent when building against Xen 4.20+.
>> >>
>> >> Signed-off-by: Adam Williamson <awilliam@redhat.com>
>> >> ---
>> >>  hw/xen/xen_pt.c | 1 +
>> >>  1 file changed, 1 insertion(+)
>> >>
>> >> diff --git a/hw/xen/xen_pt.c b/hw/xen/xen_pt.c
>> >> index 9d16644d82..006b5b55f2 100644
>> >> --- a/hw/xen/xen_pt.c
>> >> +++ b/hw/xen/xen_pt.c
>> >> @@ -54,6 +54,7 @@
>> >>  
>> >>  #include "qemu/osdep.h"
>> >>  #include "qapi/error.h"
>> >> +#include "qemu/error-report.h"
>> >>  #include <sys/ioctl.h>
>> >>  
>> >>  #include "hw/pci/pci.h"
>> >
>> > Uh, error-report.h is included without this for me.  To see, build with
>> > -H:
>> >
>> > . /work/armbru/qemu/hw/xen/xen_pt.h
>> > .. /work/armbru/qemu/include/hw/xen/xen_native.h
>> > ... /work/armbru/qemu/hw/xen/trace.h
>> > .... ./trace/trace-hw_xen.h
>> > ..... /work/armbru/qemu/include/qemu/error-report.h
>> 
>> Just remembered: the generated trace header includes error-report.h only
>> when trace's log backend is enabled.
>
> Hmm, that's rather an unfortunate trap-door :-( Given that 'log' is enabled
> by default when building from git we'll never see missing error-report.h
> problems in daily work.

Correct.

> Looking at the log backend it appears that originally it would
> unconditionally include the timestamp when calling qemu_log, but
> then changed that to opt-in with
>
>   commit 418ed14268f797a5142b60cd557cd598eb548c66
>   Author: Stefan Hajnoczi <stefanha@redhat.com>
>   Date:   Mon Jan 25 11:35:07 2021 +0000
>
>     trace: make the 'log' backend timestamp configurable
>
> requiring -msg timestamp=on, which was a pre-existing flag that already
> did a similar toggle for the 'error_report' function. The goal makes
> sense, but it introduced the error-report.h trap door
>
> When I see that I also question why the 'log' backend should be a
> special case user of qemu_log() ?  Why shouldn't we emit timestamps
> for all usage of qemu_log() ?
>
> If we changed the qemu_log impl to honour the timestamp toggle, then
> all users of qemu_log benefit. We then eliminate error-report.h usage
> in trace.h headers, and also cut the code size for trace points
> significantly
>
>
> static inline void _nocheck__trace_object_dynamic_cast_assert(const char * type, const char * target, const char * file, int line, const char * func)
> {
>     if (trace_event_get_state(TRACE_OBJECT_DYNAMIC_CAST_ASSERT) && qemu_loglevel_mask(LOG_TRACE)) {
>         if (message_with_timestamp) {
>             struct timeval _now;
>             gettimeofday(&_now, NULL);
>             qemu_log("%d@%zu.%06zu:object_dynamic_cast_assert " "%s->%s (%s:%d:%s)" "\n",
>                      qemu_get_thread_id(),
>                      (size_t)_now.tv_sec, (size_t)_now.tv_usec
>                      , type, target, file, line, func);
>         } else {
>             qemu_log("object_dynamic_cast_assert " "%s->%s (%s:%d:%s)" "\n", type, target, file, line, func);
>         }
>     }
> }
>
> down to
>
>
> static inline void _nocheck__trace_object_dynamic_cast_assert(const char * type, const char * target, const char * file, int line, const char * func)
> {
>     if (trace_event_get_state(TRACE_OBJECT_DYNAMIC_CAST_ASSERT) && qemu_loglevel_mask(LOG_TRACE)) {
>             qemu_log("object_dynamic_cast_assert " "%s->%s (%s:%d:%s)" "\n", type, target, file, line, func);
>     }
> }
>
> which feels more in keeping with the kind of level of complexity you should
> want to be inlined in trace callers.

Oh yes.  We should do this even if we find a reason for keeping
qemu_log() as it is.  The obvious way would be a new function
qemu_log_with_timestamp().