Re: [Qemu-devel] QEMU postcopy-test failing on ppc64

[Thomas Huth]

On 15.11.2016 19:13, Greg Kurz wrote:
> On Tue, 15 Nov 2016 17:43:39 +0000
> "Dr. David Alan Gilbert" <address@hidden> wrote:
> 
>> * Thomas Huth (address@hidden) wrote:
>>> On 15.11.2016 16:18, Stefan Hajnoczi wrote:  
>>>> On Tue, Nov 15, 2016 at 2:56 PM, Greg Kurz <address@hidden> wrote:  
>>>>> On Tue, 15 Nov 2016 11:14:57 +0000
>>>>> Stefan Hajnoczi <address@hidden> wrote:
>>>>>  
>>>>>> On Tue, Nov 15, 2016 at 10:09 AM, Greg Kurz <address@hidden> wrote:  
>>>>>>> On Tue, 15 Nov 2016 10:53:35 +0100
>>>>>>> Laurent Vivier <address@hidden> wrote:
>>>>>>>  
>>>>>>>> On 14/11/2016 21:52, Stefan Hajnoczi wrote:  
>>>>>>>>> I hit a failure running "make check" on ppc64 for the first time.  
>>>>>>>>> Ideas?
>>>>>>>>>
>>>>>>>>> Stefan
>>>>>>>>>
>>>>>>>>> commit 682df581c65ed2c1b9e77093e332214ecaa1ee93
>>>>>>>>>
>>>>>>>>>   GTESTER check-qtest-ppc64
>>>>>>>>> Memory content inconsistency at 5af4000 first_byte = 1b last_byte = 1a
>>>>>>>>> current = 7c hit_edge = 1
>>>>>>>>> Memory content inconsistency at 5af5000 first_byte = 1b last_byte = 7c
>>>>>>>>> current = 1b hit_edge = 1
>>>>>>>>> Memory content inconsistency at 5e59000 first_byte = 1b last_byte = 1b
>>>>>>>>> current = 1a hit_edge = 1
>>>>>>>>> **
>>>>>>>>> ERROR:tests/postcopy-test.c:345:check_guests_ram: 'bad' should be 
>>>>>>>>> FALSE
>>>>>>>>> GTester: last random seed: R02S9d79166a1ca7e21940a0f4b0b1255d5b
>>>>>>>>>  
>>>>>>>>
>>>>>>>> Are you using KVM PR?
>>>>>>>>
>>>>>>>> it  was working fine with TCG and KVM HV.
>>>>>>>>
>>>>>>>> Apparently, USERFAULTFD doesn't work with KVM PR.
>>>>>>>>
>>>>>>>> I've already seen this kind of error with nested KVM on Power:
>>>>>>>> guest in guest with KVM PR in host.
>>>>>>>>
>>>>>>>> This problem was reported on IRC by Greg if I remember correctly (CC:)
>>>>>>>>  
>>>>>>>
>>>>>>> Yeah I hit this when running make check in a PPC64 BE guest which
>>>>>>> has kvm_pr loaded. I did not find time to investigate though... I've
>>>>>>> switched to run make check on bare metal POWER7 instead.  
>>>>>>
>>>>>> Right, it's POWER7 PPC64 BE with kvm_pr.
>>>>>>  
>>>>>
>>>>> And you cannot install a PPC64 BE distro on this POWER7 host and use
>>>>> kvm_hv instead ?  
>>>>
>>>> Sure, I could get a non-kvm_pr environment.  I'm just concerned that
>>>> QEMU 2.8-rc0 is being tagged today and there is a POWER environment
>>>> where "make check" fails.
>>>>
>>>> Is kvm_pr supported by QEMU?  
>>>
>>> Basically yes, it's just like Greg said in another mail, it does not get
>>> much attention these days.
>>>   
>>>> If it is supported then "make check" ought to pass.  
>>>
>>> OK, since nobody got a really, really good idea how to fix this so far:
>>> What about changing the QEMU test to use only tcg for now, so we've got
>>> a clean release with QEMU v2.8? And then afterwards, we can either fix
>>> kvm-pr in the kernel, or introduce some other mechanism to select
>>> whether the test should be run with KVM or not (either a detection of
>>> the KVM type, or an environment variable or something similar).  
>>
>> I'm OK if you want to do that for Power; I'd prefer it kept preferring KVM on
>> x86.
> 
> Even for Power, I'd prefer to keep KVM since the problem only happens with
> KVM PR which isn't the preferred way to do KVM on bare metal... until this
> get fixed, I'd rather suggest people to run make check with KVM HV.

OK ... what do you think about a patch like this:

diff --git a/tests/postcopy-test.c b/tests/postcopy-test.c
--- a/tests/postcopy-test.c
+++ b/tests/postcopy-test.c
@@ -380,17 +380,19 @@ static void test_migrate(void)
                                   " -incoming %s",
                                   tmpfs, bootpath, uri);
     } else if (strcmp(arch, "ppc64") == 0) {
+        const char *accel;
         init_bootfile_ppc(bootpath);
-        cmd_src = g_strdup_printf("-machine accel=kvm:tcg -m 256M"
+        accel = system("/sbin/lsmod | grep -q kvm_hv") ? "tcg" : "kvm:tcg";
+        cmd_src = g_strdup_printf("-machine accel=%s -m 256M"
                                   " -name pcsource,debug-threads=on"
                                   " -serial file:%s/src_serial"
                                   " -drive file=%s,if=pflash,format=raw",
-                                  tmpfs, bootpath);
-        cmd_dst = g_strdup_printf("-machine accel=kvm:tcg -m 256M"
+                                  accel, tmpfs, bootpath);
+        cmd_dst = g_strdup_printf("-machine accel=%s -m 256M"
                                   " -name pcdest,debug-threads=on"
                                   " -serial file:%s/dest_serial"
                                   " -incoming %s",
-                                  tmpfs, uri);
+                                  accel, tmpfs, uri);
     } else {
         g_assert_not_reached();
     }

That way, accel=kvm:tcg is only used if the kvm_hv module is loaded,
otherwise it will use accel=tcg instead.

 Thomas