linux-kernel - Re: [PATCH v3 2/6] vfio: ccw: Rework subchannel state on setup

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Date:   Wed, 19 Dec 2018 10:51:03 +0100
From:   Pierre Morel <pmorel@...ux.ibm.com>
To:     Eric Farman <farman@...ux.ibm.com>, pasic@...ux.vnet.ibm.com
Cc:     cohuck@...hat.com, alifm@...ux.ibm.com, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v3 2/6] vfio: ccw: Rework subchannel state on setup

On 18/12/2018 18:44, Eric Farman wrote:
> My questions to this patch from the original RFC series are still 
> outstanding.  :(
> 
> https://marc.info/?l=linux-s390&m=154223063716128&w=2


Hi Eric,

Thanks for the following of this patch series.

For your question about quiece during remove I do not think it should be 
a NOP, we must make sure the channel is disabled at that time.

> 
> On 11/28/2018 07:41 AM, Pierre Morel wrote:
>> The subchannel enablement and the according setting to the
>> VFIO_CCW_STATE_STANDBY state should only be done when all
>> parts of the VFIO mediated device have been initialized
>> i.e. after the mediated device has been successfully opened.
>>
>> Let's stay in VFIO_CCW_STATE_NOT_OPER until the mediated
>> device has been opened and set the VFIO_CCW_STATE_STANDBY
>> on a successful open.
>>
>> On release the state is set back to VFIO_CCW_STATE_NOT_OPER
>> by vfio_ccw_sch_quiesce().
>>
>> When the mediated device is closed,  disable the sub channel
>> by calling vfio_ccw_sch_quiesce().
>>
>> Signed-off-by: Pierre Morel <pmorel@...ux.ibm.com>
>> ---
>>   drivers/s390/cio/vfio_ccw_async.c   | 11 +++++++++++
> 
> Ah, this series is built on Connie's async changes.  Okay.  [1]

Yes, and after reflections I think the timing is bad so I prefer to wait 
for the series from Connie on hsch/csch to be finished before going on 
with this series.
Otherwise I fear to only add noise to the current discussions.


> 
>>   drivers/s390/cio/vfio_ccw_drv.c     | 10 +---------
>>   drivers/s390/cio/vfio_ccw_ops.c     | 27 +++++++++++++++++++++------
...snip...
>> @@ -170,6 +184,7 @@ static void vfio_ccw_mdev_release(struct 
>> mdev_device *mdev)
>>           dev_get_drvdata(mdev_parent_dev(mdev));
>>       int i;
>> +    vfio_ccw_sch_quiesce(private->sch);
>>       vfio_unregister_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,
>>                    &private->nb);
> 
> [1] If Connie's async patches go in first, then the stuff in your 
> "vfio_ccw_unregister_async_dev_regions" is also added here.  That could 
> be removed and replaced with a call to your new function, yes?

certainly.
Thanks for your comments.

Regards,
Pierre


-- 
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany