Re: [Qemu-devel] [PATCH v5 2/4] shutdown: Prepare for use of an enum in reset/shutdown_request

[Markus Armbruster <armbru@redhat.com>]

"Dr. David Alan Gilbert" <dgilbert@redhat.com> writes:

> * Eric Blake (eblake@redhat.com) wrote:
>> We want to track why a guest was shutdown; in particular, being able
>> to tell the difference between a guest request (such as ACPI request)
>> and host request (such as SIGINT) will prove useful to libvirt.
>> Since all requests eventually end up changing shutdown_requested in
>> vl.c, the logical change is to make that value track the reason,
>> rather than its current 0/1 contents.
>> 
>> Since command-line options control whether a reset request is turned
>> into a shutdown request instead, the same treatment is given to
>> reset_requested.
>> 
>> This patch adds a QAPI enum ShutdownCause that describes reasons
>> that a shutdown can be requested, and changes qemu_system_reset() to
>> pass the reason through, although for now it is not reported.  The
>> next patch will actually wire things up to modify events to report
>> data based on the reason, and to pass the correct enum value in from
>> various call-sites that can trigger a reset/shutdown.  Since QAPI
>> generates enums starting at 0, it's easier if we use a different
>> number as our sentinel that no request has happened yet.  Most of
>> the changes are in vl.c, but xen was using things externally.
>> 
>> Signed-off-by: Eric Blake <eblake@redhat.com>
>> 
>> ---
>> v4: s/ShutdownType/ShutdownCause/, no thanks to mingw header pollution
>> v3: new patch
>> ---
>>  qapi-schema.json        | 23 +++++++++++++++++++++++
>>  include/sysemu/sysemu.h |  2 +-
>>  vl.c                    | 44 ++++++++++++++++++++++++++++----------------
>>  hw/i386/xen/xen-hvm.c   |  9 ++++++---
>>  migration/colo.c        |  2 +-
>>  migration/savevm.c      |  2 +-
>>  6 files changed, 60 insertions(+), 22 deletions(-)
>> 
>> diff --git a/qapi-schema.json b/qapi-schema.json
>> index 01b087f..a4ebdd1 100644
>> --- a/qapi-schema.json
>> +++ b/qapi-schema.json
>> @@ -2304,6 +2304,29 @@
>>  { 'command': 'system_powerdown' }
>> 
>>  ##
>> +# @ShutdownCause:
>> +#
>> +# Enumeration of various causes for shutdown.
>> +#
>> +# @host-qmp: Reaction to a QMP command, such as 'quit'
>> +# @host-signal: Reaction to a signal, such as SIGINT
>> +# @host-ui: Reaction to a UI event, such as closing the window
>> +# @host-replay: The host is replaying an earlier shutdown event
>> +# @host-error: Qemu encountered an error that prevents further use of the guest
>> +# @guest-shutdown: The guest requested a shutdown, such as via ACPI or
>> +#                  other hardware-specific action
>> +# @guest-reset: The guest requested a reset, and the command line
>> +#               response to a reset is to instead trigger a shutdown
>> +# @guest-panic: The guest panicked, and the command line response to
>> +#               a panic is to trigger a shutdown
>
> It's a little coarse grained;  is there anyway to pass platform specific information
> for debug?  I ask because I spent a while debugging a few bugs with unexpected
> resets and had to figure out which of x86's many reset causes triggered it.

Asking for more help with debugging is fair, but I think the need is
better served by tracepoints than by exposing even more detail in QMP,
where compatibility promises apply.