From: Pierre Morel <pmorel@linux.ibm.com>
To: Cornelia Huck <cohuck@redhat.com>,
Pierre Morel <pmorel@linux.vnet.ibm.com>
Cc: Dong Jia Shi <bjsdjshi@linux.ibm.com>,
Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>,
pasic@linux.vnet.ibm.com, linux-s390@vger.kernel.org,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH 04/10] vfio: ccw: replace IO_REQ event with SSCH_REQ event
Date: Wed, 23 May 2018 09:50:00 +0200 [thread overview]
Message-ID: <86a4be7f-6c4c-19db-f743-ed4af0173125@linux.ibm.com> (raw)
In-Reply-To: <20180522174120.2a56adb7.cohuck@redhat.com>
On 22/05/2018 17:41, Cornelia Huck wrote:
> On Fri, 4 May 2018 13:02:36 +0200
> Pierre Morel <pmorel@linux.vnet.ibm.com> wrote:
>
>> On 04/05/2018 03:19, Dong Jia Shi wrote:
>>> * Pierre Morel <pmorel@linux.vnet.ibm.com> [2018-05-03 16:26:29 +0200]:
>>>
>>>> On 02/05/2018 09:46, Dong Jia Shi wrote:
>>>>> * Cornelia Huck <cohuck@redhat.com> [2018-04-30 17:33:05 +0200]:
>>>>>
>>>>>> On Thu, 26 Apr 2018 15:48:06 +0800
>>>>>> Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com> wrote:
>>>>>>
>>>>>>> * Dong Jia Shi <bjsdjshi@linux.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?
>>> As far as I see, that's not true. ;)
>>>
>>> After this series applied,
>>> vfio_ccw_jumptable[VFIO_CCW_STATE_STANDBY][VFIO_CCW_EVENT_INTERRUPT] is
>>> still fsm_irq().
>>>
>>
>> What I mean is, this code tries to handle design problems
>> without changing too much of the original code at first.
>>
>> The problem here is not that the fsm_irq function is called on interrupt,
>> if we have an interrupt it must be signaled to user land.
>> The problem is that this state is entered at the wrong moment.
>>
>> STANDBY should be entered, during the mdev_open when we realize the QEMU
>> device,
>> and not during the probe, in which we should stay in NOT_OPER until we
>> get the QEMU device.
>>
>> The probe() and mdev_open() function should be modified, not the state
>> table.
> So, the takeaway is that we should handle starting via the init
> callbacks and not via the state machine?
>
hum, sorry, I think that my previous answer was not completely right,
and did not really answer to Dong Jia comment, yes fsm_irq was not
at its place, thinking again about the comments of both of you
I think that we can suppress the INIT event.
I would like to rebase the patch to include the comments you both did.
--
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany
next prev parent reply other threads:[~2018-05-23 7:50 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-19 14:48 [PATCH 00/10] vfio: ccw: Refactoring the VFIO CCW state machine Pierre Morel
2018-04-19 14:48 ` [PATCH 01/10] vfio: ccw: Moving state change out of IRQ context Pierre Morel
[not found] ` <20180424065442.GV12194@bjsdjshi@linux.vnet.ibm.com>
2018-04-24 8:40 ` Pierre Morel
2018-04-24 9:59 ` Cornelia Huck
2018-04-24 11:49 ` Pierre Morel
2018-04-24 11:55 ` Cornelia Huck
2018-04-24 13:07 ` Pierre Morel
2018-04-24 16:42 ` Halil Pasic
2018-04-25 6:57 ` Cornelia Huck
2018-04-25 11:06 ` Halil Pasic
2018-04-30 13:56 ` Cornelia Huck
2018-04-19 14:48 ` [PATCH 02/10] vfio: ccw: Transform FSM functions to return state Pierre Morel
[not found] ` <20180424072550.GW12194@bjsdjshi@linux.vnet.ibm.com>
2018-04-24 8:22 ` Pierre Morel
2018-04-30 13:58 ` Cornelia Huck
2018-04-19 14:48 ` [PATCH 03/10] vfio: ccw: new SCH_EVENT event Pierre Morel
2018-04-25 8:25 ` Cornelia Huck
2018-04-25 13:54 ` Pierre Morel
[not found] ` <20180426065954.GP5428@bjsdjshi@linux.vnet.ibm.com>
2018-04-30 15:28 ` Cornelia Huck
2018-05-04 8:25 ` Pierre Morel
2018-04-19 14:48 ` [PATCH 04/10] vfio: ccw: replace IO_REQ event with SSCH_REQ event Pierre Morel
2018-04-25 8:41 ` Cornelia Huck
[not found] ` <24f638e4-2f7e-00e1-1efb-ff3fe524bca0@linux.vnet.ibm.com>
2018-04-30 15:30 ` Cornelia Huck
2018-05-03 12:06 ` Pierre Morel
2018-05-22 15:38 ` Cornelia Huck
2018-05-23 8:19 ` Pierre Morel
[not found] ` <20180426073053.GZ12194@bjsdjshi@linux.vnet.ibm.com>
[not found] ` <20180426074806.GB12194@bjsdjshi@linux.vnet.ibm.com>
2018-04-30 15:33 ` Cornelia Huck
[not found] ` <20180502074622.GV5428@bjsdjshi@linux.vnet.ibm.com>
2018-05-02 8:22 ` Cornelia Huck
2018-05-03 14:26 ` Pierre Morel
[not found] ` <20180504011916.GA26081@bjsdjshi@linux.ibm.com>
2018-05-04 11:02 ` Pierre Morel
2018-05-22 15:41 ` Cornelia Huck
2018-05-23 7:50 ` Pierre Morel [this message]
2018-05-23 8:10 ` Cornelia Huck
2018-04-19 14:48 ` [PATCH 05/10] vfio: ccw: Suppress unused event parameter Pierre Morel
[not found] ` <20180426073618.GA12194@bjsdjshi@linux.vnet.ibm.com>
2018-05-03 10:34 ` Pierre Morel
2018-04-19 14:48 ` [PATCH 06/10] vfio: ccw: Make FSM functions atomic Pierre Morel
2018-04-19 14:48 ` [PATCH 07/10] vfio: ccw: Introduce the INIT event Pierre Morel
2018-04-30 15:39 ` Cornelia Huck
2018-05-03 10:31 ` Pierre Morel
2018-04-19 14:48 ` [PATCH 08/10] vfio: ccw: Handling reset and shutdown with states Pierre Morel
2018-04-30 15:43 ` Cornelia Huck
2018-04-19 14:48 ` [PATCH 09/10] vfio: ccw: Suppressing the BOXED state Pierre Morel
2018-04-25 8:44 ` Cornelia Huck
2018-04-25 13:55 ` Pierre Morel
2018-04-30 15:47 ` Cornelia Huck
2018-05-03 9:02 ` Pierre Morel
2018-04-19 14:48 ` [PATCH 10/10] vfio: ccw: Let user wait when busy on IO Pierre Morel
2018-04-25 8:48 ` Cornelia Huck
2018-04-25 14:00 ` Pierre Morel
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