linux-kernel - Re: [PATCH v7 2/2] s390: virtio: PV needs VIRTIO I/O device protection

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Date:   Thu, 6 Aug 2020 16:19:23 +0200
From:   Pierre Morel <pmorel@...ux.ibm.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>
Cc:     linux-kernel@...r.kernel.org, pasic@...ux.ibm.com,
        borntraeger@...ibm.com, frankja@...ux.ibm.com, cohuck@...hat.com,
        kvm@...r.kernel.org, linux-s390@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, thomas.lendacky@....com,
        david@...son.dropbear.id.au, linuxram@...ibm.com,
        hca@...ux.ibm.com, gor@...ux.ibm.com
Subject: Re: [PATCH v7 2/2] s390: virtio: PV needs VIRTIO I/O device
 protection



On 2020-07-30 13:31, Pierre Morel wrote:
...snip...
>>>> What bothers me here is that arch code depends on virtio now.
>>>> It works even with a modular virtio when functions are inline,
>>>> but it seems fragile: e.g. it breaks virtio as an out of tree module,
>>>> since layout of struct virtio_device can change.
>>>
>>>
>>> The code was only called from virtio.c so it should be fine.
>>>
>>> And my understanding is that we don't need to care about the kABI issue
>>> during upstream development?
>>>
>>> Thanks
>>
>> No, but so far it has been convenient at least for me, for development,
>> to just be able to unload all of virtio and load a different version.
>>
>>
>>>
>>>>
>>>> I'm not sure what to do with this yet, will try to think about it
>>>> over the weekend. Thanks!

After reflection, I am not sure that this problem must be treated on the 
architecture level or inside the VIRTIO transport.
Consequently, I will propose another patch series based on CCW transport.
This also should be more convenient for core development.

Regards,
Pierre

-- 
Pierre Morel
IBM Lab Boeblingen