Re: [Qemu-devel] [PATCH 3/6] s390/kvm: diag288 instruction interception and handling

[Alexander Graf <agraf@suse.de>]

On 04/22/2015 10:32 AM, Cornelia Huck wrote:
> On Tue, 21 Apr 2015 21:09:05 +0200
> Alexander Graf <agraf@suse.de> wrote:
>
>> On 04/17/2015 09:52 AM, Cornelia Huck wrote:
>>> From: Xu Wang <gesaint@linux.vnet.ibm.com>
>>>
>>> Intercept the diag288 requests from kvm guests, and hand the
>>> requested command to the diag288 watchdog device for further
>>> handling.
>>>
>>> Signed-off-by: Xu Wang <gesaint@linux.vnet.ibm.com>
>>> Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
>>> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
>> We're getting a lot of random devices allocating diag intercepts. Can't
>> we make this an actual interface, similar to the hypercall registration
>> on sPAPR?
> I've looked at the sPAPR hcall code, and it seems to basically provide
> a table with a nice registration interface (we already use something
> similar for the diagnose 500 virtio subcodes, btw.)
>
> While we could move our basic diagnose handling over to a table-like
> approach and registering new diagnoses, I think this is orthogonal to
> introducing a diag288 watchdog device: It just makes sense to model the
> watchdog as a device that just happens to be poked via a diagnose. If
> we introduce any further diagnoses to manipulate timing etc., I agree
> we don't want to add a device for each of these.

My thinking was in the opposite level. I really like the idea of having 
separate devices for each function. But I think that they should be 
completely self-contained with well defined interfaces.


Alex