Re: [Qemu-devel] [PATCH] virtio-blk: switch off scsi-passthrough by default

[Paolo Bonzini <pbonzini@redhat.com>]

On 16/10/2015 10:54, Cornelia Huck wrote:
> On Fri, 16 Oct 2015 10:46:31 +0200
> Paolo Bonzini <pbonzini@redhat.com> wrote:
> 
>>
>>
>> On 16/10/2015 10:41, Paolo Bonzini wrote:
>>>
>>>
>>> On 16/10/2015 10:40, Cornelia Huck wrote:
>>>> --- a/hw/s390x/s390-virtio-ccw.c
>>>> +++ b/hw/s390x/s390-virtio-ccw.c
>>>> @@ -272,6 +272,10 @@ static const TypeInfo ccw_machine_info = {
>>>>              .driver   = "vhost-scsi-ccw",\
>>>>              .property = "max_revision",\
>>>>              .value    = "0",\
>>>> +        },{\
>>>> +            .driver   = "virtio-blk-ccw",\
>>>> +            .property = "scsi",\
>>>> +            .value    = "true",\
>>>>          },
>>>>  
>>>>  static void ccw_machine_2_4_class_init(ObjectClass *oc, void *data)
>>>> diff --git a/include/hw/compat.h b/include/hw/compat.h
>>>> index 095de5d..bbf1ab2 100644
>>>> --- a/include/hw/compat.h
>>>> +++ b/include/hw/compat.h
>>>> @@ -2,7 +2,11 @@
>>>>  #define HW_COMPAT_H
>>>>  
>>>>  #define HW_COMPAT_2_4 \
>>>> -        /* empty */
>>>> +        {\
>>>> +            .driver   = "virtio-blk-pci",\
>>>> +            .property = "scsi",\
>>>> +            .value    = "true",\
>>>> +        },
>>>>  
>>>>  #define HW_COMPAT_2_3 \
>>>>          {\
>>>>
>>>
>>> s390 should use HW_COMPAT_2_4 as well.  Otherwise looks good.
>>
>> Hmm, ECONCISE probably.  Sorry.
>>
>> I mean that virtio-blk-ccw's scsi property should IMO go in
>> HW_COMPAT_2_4 as well.
> 
> I was wondering about the semantics of HW_COMPAT_*: Does any hw-related
> compat stuff go in there, even if it is architecture specific (like
> ccw)?

It depends.  For stuff like your max_revision I guess it makes sense to
keep it in the board.  Similarly, x86 CPU flags go in PC_COMPAT_*.  But
for stuff like virtio-blk-ccw, it makes some sense to keep it close to
virtio-blk-pci.

>> But I noticed now that:
>>
>> * if it works it would be even better if the compat property used
>> virtio-blk-device;
> 
> Hm. Previous virtio-compat always treated -pci explicitly, but we only
> gained s390x compat handling with 2.4, so it didn't really matter. But
> if it works, this is the saner approach.

Yes, I agree.

Paolo