Re: [PATCH 09/10] vfio: ccw: Suppressing the BOXED state

From: Pierre Morel <pmorel@linux.vnet.ibm.com>
To: Cornelia Huck <cohuck@redhat.com>
Cc: pasic@linux.vnet.ibm.com, bjsdjshi@linux.vnet.ibm.com,
	linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
	kvm@vger.kernel.org
Subject: Re: [PATCH 09/10] vfio: ccw: Suppressing the BOXED state
Date: Thu, 3 May 2018 11:02:33 +0200	[thread overview]
Message-ID: <0d95b955-1567-cead-35d2-9d784b74ffa0@linux.vnet.ibm.com> (raw)
In-Reply-To: <20180430174718.7b1e5651.cohuck@redhat.com>

On 30/04/2018 17:47, Cornelia Huck wrote:
> On Wed, 25 Apr 2018 15:55:51 +0200
> Pierre Morel <pmorel@linux.vnet.ibm.com> wrote:
>
>> On 25/04/2018 10:44, Cornelia Huck wrote:
>>> On Thu, 19 Apr 2018 16:48:12 +0200
>>> Pierre Morel <pmorel@linux.vnet.ibm.com> wrote:
>>>   
>>>> VFIO_CCW_STATE_BOXED and VFIO_CCW_STATE_BUSY are the same
>>>> states.
>>>> Let's only keep one: VFIO_CCW_STATE_BUSY
>>>>
>>>> Signed-off-by: Pierre Morel <pmorel@linux.vnet.ibm.com>
>>>> ---
>>>>    drivers/s390/cio/vfio_ccw_fsm.c     | 9 ---------
>>>>    drivers/s390/cio/vfio_ccw_private.h | 1 -
>>>>    2 files changed, 10 deletions(-)
>>> I think they were initially supposed to cover two different things:
>>> - BUSY: we're currently dealing with an I/O request
>>> - BOXED: the device currently won't talk to us or we won't talk to it
>>>
>>> It seems we never really did anything useful with BOXED; but should we?
>>>   
>> I do not know what.
> The BUSY state is something we know that we'll get out of soon-ish
> (when the I/O request has finished). We could conceivably use a timeout
> and drop to the BOXED state if we don't get an answer.

Absolutely, timeout on requests is something I wanted to do in a second 
series.

>
> I think this plays also into the reserve/release and path handling
> questions. One of the more common reasons for devices to become boxed
> I've seen is another system doing a reserve on a dasd.
>

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