Re: [Qemu-devel] [PULL 40/50] spapr_events: add support for phb hotplug events

[Thomas Huth <thuth@redhat.com>]

On 01/03/2019 11.48, Greg Kurz wrote:
> On Fri, 1 Mar 2019 11:30:18 +0100
> David Hildenbrand <david@redhat.com> wrote:
> 
>> On 01.03.19 02:31, Michael Roth wrote:
>>> Quoting Thomas Huth (2019-02-28 12:40:52)  
>>>> On 26/02/2019 05.52, David Gibson wrote:  
>>>>> From: Michael Roth <mdroth@linux.vnet.ibm.com>
>>>>>
>>>>> Extend the existing EPOW event format we use for PCI
>>>>> devices to emit PHB plug/unplug events.
>>>>>
>>>>> Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
>>>>> Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
>>>>> Signed-off-by: Greg Kurz <groug@kaod.org>
>>>>> Message-Id: <155059671405.1466090.535964535260503283.stgit@bahia.lab.toulouse-stg.fr.ibm.com>
>>>>> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
>>>>> ---
>>>>>  hw/ppc/spapr_events.c | 3 +++
>>>>>  1 file changed, 3 insertions(+)
>>>>>
>>>>> diff --git a/hw/ppc/spapr_events.c b/hw/ppc/spapr_events.c
>>>>> index b9c7ecb9e9..ab9a1f0063 100644
>>>>> --- a/hw/ppc/spapr_events.c
>>>>> +++ b/hw/ppc/spapr_events.c
>>>>> @@ -526,6 +526,9 @@ static void spapr_hotplug_req_event(uint8_t hp_id, uint8_t hp_action,
>>>>>      case SPAPR_DR_CONNECTOR_TYPE_CPU:
>>>>>          hp->hotplug_type = RTAS_LOG_V6_HP_TYPE_CPU;
>>>>>          break;
>>>>> +    case SPAPR_DR_CONNECTOR_TYPE_PHB:
>>>>> +        hp->hotplug_type = RTAS_LOG_V6_HP_TYPE_PHB;
>>>>> +        break;
>>>>>      default:
>>>>>          /* we shouldn't be signaling hotplug events for resources
>>>>>           * that don't support them  
>>>>
>>>> I think this patch (or something else in this PULL request) broke CPU
>>>> hot-plugging with older machine types:
>>>>
>>>> $ QTEST_QEMU_BINARY=ppc64-softmmu/qemu-system-ppc64 ./tests/cpu-plug-test -m=slow
>>>> /ppc64/cpu-plug/pseries-3.1/device-add/2x3x1&maxcpus=6: OK
>>>> /ppc64/cpu-plug/pseries-2.12-sxxm/device-add/2x3x1&maxcpus=6: OK
>>>> /ppc64/cpu-plug/pseries-3.0/device-add/2x3x1&maxcpus=6: OK
>>>> /ppc64/cpu-plug/pseries-2.10/device-add/2x3x1&maxcpus=6: OK
>>>> /ppc64/cpu-plug/pseries-2.11/device-add/2x3x1&maxcpus=6: OK
>>>> /ppc64/cpu-plug/pseries-2.12/device-add/2x3x1&maxcpus=6: OK
>>>> /ppc64/cpu-plug/pseries-2.9/device-add/2x3x1&maxcpus=6: OK
>>>> /ppc64/cpu-plug/pseries-2.7/device-add/2x3x1&maxcpus=6: **
>>>> ERROR:/home/thuth/devel/qemu/hw/ppc/spapr_events.c:313:rtas_event_log_to_source: assertion failed: (source->enabled)
>>>> Broken pipe
>>>> /home/thuth/devel/qemu/tests/libqtest.c:143: kill_qemu() detected QEMU death from signal 6 (Aborted) (core dumped)
>>>> Aborted (core dumped)
>>>>
>>>> Could you please have a look?  
>>>
>>> Bisected to:
>>>
>>>   commit b8165118f52ce5ee88565d3cec83d30374efdc96
>>>   Author: David Hildenbrand <david@redhat.com>
>>>   Date:   Mon Feb 18 10:21:58 2019 +0100
>>>   
>>>       spapr: support memory unplug for qtest
>>>       
>>>       Fake availability of OV5_HP_EVT, so we can test memory unplug in qtest.
>>>
>>> Which makes sense since OV5_HP_EVT assumes that
>>> spapr->spapr->use_hotplug_event_source == true, which isn't the default for
>>> 2.7 and below.
>>>
>>> If I revert that I think I hit the bug it was meant to fix:
>>>
>>>   mdroth@sif:~/w/qemu-build3$ make V=1 check-qtest-ppc64
>>>   ...
>>>   PASS 1 device-plug-test /ppc64/device-plug/pci-unplug-request
>>>   PASS 2 device-plug-test /ppc64/device-plug/spapr-cpu-unplug-request
>>>   **
>>>   ERROR:/home/mdroth/w/qemu3.git/tests/device-plug-test.c:28:device_del_finish: assertion failed: (qdict_haskey(resp, "return"))
>>>   ERROR - Bail out! ERROR:/home/mdroth/w/qemu3.git/tests/device-plug-test.c:28:device_del_finish: assertion failed: (qdict_haskey(resp, "return"))
>>>   Aborted (core dumped)
>>>   /home/mdroth/w/qemu3.git/tests/Makefile.include:875: recipe for target 'check-qtest-ppc64' failed
>>>   make: *** [check-qtest-ppc64] Error 1
>>>   mdroth@sif:~/w/qemu-build3$
>>>
>>> Which is probably due to this check in spapr_machine_device_unplug_request():
>>>
>>>     if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
>>>         if (spapr_ovec_test(sms->ov5_cas, OV5_HP_EVT)) {
>>>             spapr_memory_unplug_request(hotplug_dev, dev, errp);
>>>         } else {
>>>             /* NOTE: this means there is a window after guest reset, prior to
>>>              * CAS negotiation, where unplug requests will fail due to the
>>>              * capability not being detected yet. This is a bit different than
>>>              * the case with PCI unplug, where the events will be queued and
>>>              * eventually handled by the guest after boot
>>>              */
>>>             error_setg(errp, "Memory hot unplug not supported for this guest");
>>>         }
>>>
>>>
>>>
>>> This spapr-cpu-unplug-request test is failing because
>>> spapr_ovec_test(sms->ov5_cas, OV5_HP_EVT) relies on the CAS-negotiated OV5 bit,
>>> which wouldn't have happened with qtest. If we want to make these tests run in
>>> this scenario we probably need a different approach than the original patch.  
>>
>> We could rip out the patch along with the spapr memory unplug test.
>> However it feels like a step back to not have any memory unplug tests
>> for QEMU at all.
>>
>> Any spapr experts here if we can work around this?
>>
> 
> Not sure about the expertise :) but I'm currently looking into it. As
> you say, it would be unfortunate to drop a test because of that.
> 

Could this work:

diff --git a/hw/ppc/spapr_ovec.c b/hw/ppc/spapr_ovec.c
--- a/hw/ppc/spapr_ovec.c
+++ b/hw/ppc/spapr_ovec.c
@@ -12,6 +12,7 @@
  */
 
 #include "qemu/osdep.h"
+#include "hw/ppc/spapr.h"
 #include "hw/ppc/spapr_ovec.h"
 #include "qemu/bitmap.h"
 #include "exec/address-spaces.h"
@@ -134,7 +135,9 @@ bool spapr_ovec_test(sPAPROptionVector *ov, long bitnr)
 
     /* support memory unplug for qtest */
     if (qtest_enabled() && bitnr == OV5_HP_EVT) {
-        return true;
+        sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
+
+        return spapr->use_hotplug_event_source;
     }
 
     return test_bit(bitnr, ov->bitmap) ? true : false;


?

 Thomas