linux-kernel - Re: [PATCH 04/10] vfio: ccw: replace IO_REQ event with SSCH

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Message-Id: <5816643d-5406-06b9-0727-fdcd771aba63@linux.vnet.ibm.com>
Date:   Thu, 3 May 2018 16:26:29 +0200
From:   Pierre Morel <pmorel@...ux.vnet.ibm.com>
To:     Dong Jia Shi <bjsdjshi@...ux.vnet.ibm.com>,
        Cornelia Huck <cohuck@...hat.com>
Cc:     pasic@...ux.vnet.ibm.com, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH 04/10] vfio: ccw: replace IO_REQ event with SSCH_REQ event

On 02/05/2018 09:46, Dong Jia Shi wrote:
> * Cornelia Huck <cohuck@...hat.com> [2018-04-30 17:33:05 +0200]:
>
>> On Thu, 26 Apr 2018 15:48:06 +0800
>> Dong Jia Shi <bjsdjshi@...ux.vnet.ibm.com> wrote:
>>
>>> * Dong Jia Shi <bjsdjshi@...ux.vnet.ibm.com> [2018-04-26 15:30:54 +0800]:
>>>
>>> [...]
>>>
>>>>> @@ -179,7 +160,7 @@ static int fsm_irq(struct vfio_ccw_private *private,
>>>>>   	if (private->io_trigger)
>>>>>   		eventfd_signal(private->io_trigger, 1);
>>>>>
>>>>> -	return private->state;
>>>>> +	return VFIO_CCW_STATE_IDLE;
>>>> This is not right. For example, if we are in STANDBY state (subch driver
>>>> is probed, but mdev device is not created), we can not jump to IDLE
>>>> state.
>>>>    
>>> I see my problem, for STANDBY state, we should introduce another event
>>> callback for VFIO_CCW_EVENT_INTERRUPT. It doesn't make sense to call
>>> fsm_irq() which tries to signal userspace with interrupt notification
>>> when mdev is not created yet... So we'd need a separated fix for this
>>> issue too.
>> But how do we even get into that situation when we don't have an mdev
>> yet?
>>
> We cann't... So let's assign fsm_nop() as the interrupt callback for
> STANDBY state?
>

:) Isn't it exactly what my patch series handle?


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