Re: [Qemu-devel] [PULL 57/60] target/ppc: add HV support for POWER9

[Philippe Mathieu-Daudé]

On 7/1/19 7:04 AM, David Gibson wrote:
> On Fri, Jun 28, 2019 at 03:20:32PM +0200, Philippe Mathieu-Daudé wrote:
>> Hi,
>>
>> On 3/12/19 8:58 PM, Cédric Le Goater wrote:
>>> On 3/12/19 8:30 PM, Cleber Rosa wrote:
>>>>> From: "Cleber Rosa" <address@hidden>
>>>>> Sent: Tuesday, March 12, 2019 3:14:09 PM
>>>>> Subject: Re: [Qemu-devel] [PULL 57/60] target/ppc: add HV support for 
>>>>> POWER9
>>>>>
>>>>> On Tue, Mar 12, 2019 at 07:34:04PM +0100, Cédric Le Goater wrote:
>>>>>> On 3/12/19 4:01 PM, Cleber Rosa wrote:
>>>>>>> On Sun, Mar 10, 2019 at 07:27:00PM +1100, David Gibson wrote:
>>>>>>>> From: Cédric Le Goater <address@hidden>
>>>>>>>>
>>>>>>>> We now have enough support to boot a PowerNV machine with a POWER9
>>>>>>>> processor. Allow HV mode on POWER9.
>>>>>>>>
>>>>>>>> Signed-off-by: Cédric Le Goater <address@hidden>
>>>>>>>> Message-Id: <address@hidden>
>>>>>>>> Signed-off-by: David Gibson <address@hidden>
>>>>>>>> ---
>>>>>>>>  target/ppc/translate_init.inc.c | 3 ++-
>>>>>>>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>>>>>>>
>>>>>>>> diff --git a/target/ppc/translate_init.inc.c
>>>>>>>> b/target/ppc/translate_init.inc.c
>>>>>>>> index af70a3b78c..0bd555eb19 100644
>>>>>>>> --- a/target/ppc/translate_init.inc.c
>>>>>>>> +++ b/target/ppc/translate_init.inc.c
>>>>>>>> @@ -8895,7 +8895,7 @@ POWERPC_FAMILY(POWER9)(ObjectClass *oc, void
>>>>>>>> *data)
>>>>>>>>                         PPC_CACHE | PPC_CACHE_ICBI | PPC_CACHE_DCBZ |
>>>>>>>>                         PPC_MEM_SYNC | PPC_MEM_EIEIO |
>>>>>>>>                         PPC_MEM_TLBSYNC |
>>>>>>>> -                       PPC_64B | PPC_64BX | PPC_ALTIVEC |
>>>>>>>> +                       PPC_64B | PPC_64H | PPC_64BX | PPC_ALTIVEC |
>>>>>>>>                         PPC_SEGMENT_64B | PPC_SLBI |
>>>>>>>>                         PPC_POPCNTB | PPC_POPCNTWD |
>>>>>>>>                         PPC_CILDST;
>>>>>>>> @@ -8907,6 +8907,7 @@ POWERPC_FAMILY(POWER9)(ObjectClass *oc, void
>>>>>>>> *data)
>>>>>>>>                          PPC2_ISA205 | PPC2_ISA207S | PPC2_FP_CVT_S64 |
>>>>>>>>                          PPC2_TM | PPC2_ISA300 | PPC2_PRCNTL;
>>>>>>>>      pcc->msr_mask = (1ull << MSR_SF) |
>>>>>>>> +                    (1ull << MSR_SHV) |
>>>>>>>>                      (1ull << MSR_TM) |
>>>>>>>>                      (1ull << MSR_VR) |
>>>>>>>>                      (1ull << MSR_VSX) |
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>> This change prevents a Fedora 29 kernel[1] from booting... is this
>>>>>>> intended or a known limitation of the Fedora 29 kernel?
>>>>>>
>>>>>> The default CPU is still power8_v2.0. This is curious.
>>>>>>
>>>>>
>>>>> Are you sure?  I'm getting:
>>>>>
>>>>>  $ git rev-parse HEAD
>>>>>  cfc3fef6b4e493bf1a7ee16790ad584e20dfbbd1
>>>>>  $ ./ppc64-softmmu/qemu-system-ppc64 -qmp unix:/tmp/qmp-sock,server
>>>>>  $ ./scripts/qmp/qom-get -s /tmp/qmp-sock 
>>>>> /machine/unattached/device[0].type
>>>>>  power9_v2.0-spapr-cpu-core
>>>
>>> That's a pseries machine, not a powernv machine. pseries should use P9
>>> processor by default but the patch above should not impact f29 on pseries. 
>>> If it does, then we have a bug. 
>>>  
>>>> Looks like the overall default is "power9_v2.0", and then on pseries-3.1 
>>>> and
>>>> lower, it's "power8_v2.0", as per 34a6b015a98.
>>>
>>> I was looking at pnv_machine_class_init() which sets the default CPU :
>>>
>>>     mc->default_cpu_type = POWERPC_CPU_TYPE_NAME("power8_v2.0");
>>
>> I found this thread while trying auto-bisection for LP#1834613:
>> https://bugs.launchpad.net/bugs/1834613
>>
>> When trying the options suggested by Laurent here:
>> https://lists.gnu.org/archive/html/qemu-devel/2019-06/msg06209.html
>>
>> this one hangs:
>>
>> $ qemu-system-ppc64 \
>>  -kernel vmlinuz-vanilla \
>>  -nographic -append "console=hvc0" \
>>  -M cap-cfpc=broken,cap-sbbc=broken,cap-ibs=broken
>>
>> but this one works:
>>
>> $ qemu-system-ppc64 \
>>  -kernel vmlinuz-vanilla \
>>  -nographic -append "console=hvc0" \
>>  -M pseries-3.1
> 
> Sorry, I missed most of this thread while on holidays.  What's the
> actual bug here?

I don't think there is a bug, this seems the result of adding a new feature.
The commit message is not obvious that old kernels won't work on the
default machine type, and we have to add the extra '-M pseries-3.1'
command line option to run such images.