Date:   Fri, 1 Nov 2019 16:04:20 -0400
From:   Tony Krowiak <akrowiak@...ux.ibm.com>
To:     Pierre Morel <pmorel@...ux.ibm.com>,
        Harald Freudenberger <freude@...ux.ibm.com>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     heiko.carstens@...ibm.com, gor@...ux.ibm.com,
        borntraeger@...ibm.com, cohuck@...hat.com, mjrosato@...ux.ibm.com,
        pasic@...ux.ibm.com, jjherne@...ux.ibm.com
Subject: Re: [PATCH] s390: vfio-ap: disable IRQ in remove callback results in
 kernel OOPS

On 10/30/19 2:02 PM, Pierre Morel wrote:
> 
> On 10/30/19 5:51 PM, Tony Krowiak wrote:
>> On 10/30/19 10:00 AM, Pierre Morel wrote:
>>>
>>>
>>>
>>> On 10/30/19 8:44 AM, Harald Freudenberger wrote:
>>>> On 29.10.19 23:09, Tony Krowiak wrote:
>>>>> From: aekrowia <akrowiak@...ux.ibm.com>
>>>>>
>>>>> When an AP adapter card is configured off via the SE or the SCLP
>>>>> Deconfigure Adjunct Processor command and the AP bus subsequently 
>>>>> detects
>>>>> that the adapter card is no longer in the AP configuration, the card
>>>>> device representing the adapter card as well as each of its associated
>>>>> AP queue devices will be removed by the AP bus. If one or more of the
>>>>> affected queue devices is bound to the VFIO AP device driver, its 
>>>>> remove
>>>>> callback will be invoked for each queue to be removed. The remove 
>>>>> callback
>>>>> resets the queue and disables IRQ processing. If interrupt 
>>>>> processing was
>>>>> never enabled for the queue, disabling IRQ processing will fail 
>>>>> resulting
>>>>> in a kernel OOPS.
>>>>>
>>>>> This patch verifies IRQ processing is enabled before attempting to 
>>>>> disable
>>>>> interrupts for the queue.
>>>>>
>>>>> Signed-off-by: Tony Krowiak <akrowiak@...ux.ibm.com>
>>>>> Signed-off-by: aekrowia <akrowiak@...ux.ibm.com>
>>>>> ---
>>>>>   drivers/s390/crypto/vfio_ap_drv.c | 3 ++-
>>>>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/drivers/s390/crypto/vfio_ap_drv.c 
>>>>> b/drivers/s390/crypto/vfio_ap_drv.c
>>>>> index be2520cc010b..42d8308fd3a1 100644
>>>>> --- a/drivers/s390/crypto/vfio_ap_drv.c
>>>>> +++ b/drivers/s390/crypto/vfio_ap_drv.c
>>>>> @@ -79,7 +79,8 @@ static void vfio_ap_queue_dev_remove(struct 
>>>>> ap_device *apdev)
>>>>>       apid = AP_QID_CARD(q->apqn);
>>>>>       apqi = AP_QID_QUEUE(q->apqn);
>>>>>       vfio_ap_mdev_reset_queue(apid, apqi, 1);
>>>>> -    vfio_ap_irq_disable(q);
>>>>> +    if (q->saved_isc != VFIO_AP_ISC_INVALID)
>>>>> +        vfio_ap_irq_disable(q);
>>>>>       kfree(q);
>>>>>       mutex_unlock(&matrix_dev->lock);
>>>>>   }
>>>> Reset of an APQN does also clear IRQ processing. I don't say that the
>>>> resources associated with IRQ handling for the APQN are also cleared.
>>>> But when you call PQAP(AQIC) after an PQAP(RAPQ) or PQAP(ZAPQ)
>>>> it is superfluous. However, there should not appear any kernel OOPS.
>>>> So can you please give me more details about this kernel oops - maybe
>>>> I need to add exception handler code to the inline ap_aqic() function.
>>>>
>>>> regards, Harald Freudenberger
>>>>
>>>
>>> Hi Tony,
>>>
>>> wasn't it already solved by the patch 5c4c2126  from Christian ?
>>
>> No, that patch merely sets the 'matrix_mdev' field of the
>> 'struct vfio_ap_queue' to NULL in the vfio_ap_free_aqic_resources()
>> function. Also, with the latest master branch which has 5c4c2126
>> installed, the failure occurs.
>>
>>>
>>> Can you send the trace to me please?
>>
>> [  266.989476] crw_info : CRW reports slct=0, oflw=0, chn=0, rsc=B, 
>> anc=0, erc=0, rsid=0
>> [  266.989617] ------------[ cut here ]------------
>> [  266.989622] vfio_ap_wait_for_irqclear: tapq rc 03: 0504
>> [  266.989681] WARNING: CPU: 0 PID: 7 at 
>> drivers/s390/crypto/vfio_ap_ops.c:101 vfio_ap_irq_disable+0x13c/0x1b0 
>> [vfio_ap]
> 
> 
> Hi Tony,
> 
> This is not a oops this is the warning written in 
> vfio_ap_wait_for_irqclear() because the AP has been deconfigured.
> 
> Note that, IIUC, this (the warning) does not happen for devices bound to 
> the vfio_ap driver but not currently assigned to a mediated device.
> 
> I do not think we should avoid sending a warning in this case because 
> this is not a normal administration good practice to forcefully take an 
> AP away like this without smoothly removing the device from the mediated 
> device.
> 
> Regards,
> 
> Pierre

After further review, I see this warning is actually issued as a
WARN_ONCE in the vfio_ap_wait_for_irqclear() function when the
PQAP(TAPQ) returns with response code 3, AP adapter deconfigured.
I wasn't aware that the WARN_ONCE macro put out a stack trace.
That doesn't negate the fact that it makes no sense to disable
interrupts if they are not enabled, nor does it make sense to
disable interrrupts subsequent to a reset because the reset will
disable interrupts. For now, this patch can be ignored pending
further review of these issues.

> 
> 
>> [ 266.989682] Modules linked in: xt_CHECKSUM xt_MASQUERADE tun bridge 
>> stp llc ip6t_rpfilter ip6t_REJECT nf_reject_ipv6 xt_conntrack 
>> ebtable_nat ip6table_nat ip6table_mangle ip6table_raw 
>> ip6table_security iptable_nat nf_nat iptable_mangle iptable_raw 
>> iptable_security nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 libcrc32c 
>> ip_set nfnetlink ebtable_filter ebtables ip6table_filter ip6_tables 
>> sunrpc ghash_s390 prng aes_s390 des_s390 libdes vfio_ccw sha512_s390 
>> sha1_s390 eadm_sch zcrypt_cex4 qeth_l2 crc32_vx_s390 dasd_eckd_mod 
>> sha256_s390 qeth sha_common dasd_mod ccwgroup qdio pkey zcrypt vfio_ap 
>> kvm
>> [  266.989704] CPU: 0 PID: 7 Comm: kworker/0:1 Not tainted 5.4.0-rc5 #81
>> [  266.989705] Hardware name: IBM 2964 NE1 749 (LPAR)
>> [  266.989710] Workqueue: events_long ap_scan_bus
>> [  266.989711] Krnl PSW : 0704c00180000000 000003ff8007d89c 
>> (vfio_ap_irq_disable+0x13c/0x1b0 [vfio_ap])
>> [  266.989714]            R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 
>> CC:0 PM:0 RI:0 EA:3
>> [  266.989716] Krnl GPRS: 000000000000000a 0000000000000006 
>> 000000000000002b 0000000000000007
>> [  266.989717]            0000000000000007 000000007fe06000 
>> 000003ff00000005 0000000000000000
>> [  266.989718]            0000000100000504 0000000000000003 
>> 00000001f9d27e40 000003e00003bb5c
>> [  266.989719]            00000001fe765d00 0000000000000504 
>> 000003ff8007d898 000003e00003ba60
>> [  266.989724] Krnl Code: 000003ff8007d88c: c02000000ce6    larl 
>> %r2,3ff8007f258
>>                           000003ff8007d892: c0e5fffff4c7    brasl 
>> %r14,3ff8007c220
>>                          #000003ff8007d898: a7f40001        brc 
>> 15,3ff8007d89a
>>                          >000003ff8007d89c: a7f4ff9d        brc 
>> 15,3ff8007d7d6
>>                           000003ff8007d8a0: a7100100 tmlh    %r1,256
>>                           000003ff8007d8a4: a784ff99        brc 
>> 8,3ff8007d7d6
>>                           000003ff8007d8a8: a7290014 lghi    %r2,20
>>                           000003ff8007d8ac: c0e5fffff4b0    brasl 
>> %r14,3ff8007c20c
>> [  266.989772] Call Trace:
>> [  266.989777] ([<000003ff8007d898>] vfio_ap_irq_disable+0x138/0x1b0 
>> [vfio_ap])
>> [  266.989779]  [<000003ff8007c4d2>] 
>> vfio_ap_queue_dev_remove+0x6a/0x90 [vfio_ap]
>> [  266.989782]  [<00000000bf0f24f0>] ap_device_remove+0x50/0x110
>> [  266.989784]  [<00000000beffbaac>] 
>> device_release_driver_internal+0x114/0x1f0
>> [  266.989787]  [<00000000beff9c88>] bus_remove_device+0x108/0x190
>> [  266.989789]  [<00000000beff5418>] device_del+0x178/0x3a0
>> [  266.989790]  [<00000000beff5670>] device_unregister+0x30/0x90
>> [  266.989791]  [<00000000bf0f0f04>] 
>> __ap_queue_devices_with_id_unregister+0x44/0x50
>> [  266.989793]  [<00000000beff86ea>] bus_for_each_dev+0x82/0xb0
>> [  266.989794]  [<00000000bf0f2aba>] ap_scan_bus+0x262/0x878
>> [  266.989798]  [<00000000beb4785c>] process_one_work+0x1e4/0x410
>> [  266.989800]  [<00000000beb47ca8>] worker_thread+0x220/0x460
>> [  266.989802]  [<00000000beb4e99a>] kthread+0x12a/0x160
>> [  266.989805]  [<00000000bf2d8eb0>] ret_from_fork+0x28/0x2c
>> [  266.989806]  [<00000000bf2d8eb4>] kernel_thread_starter+0x0/0xc
>> [  266.989807] Last Breaking-Event-Address:
>> [  266.989809]  [<000003ff8007d898>] vfio_ap_irq_disable+0x138/0x1b0 
>> [vfio_ap]
>> [  266.989810] ---[ end trace 59b4020890dbd391 ]---
>>
>>
>>>
>>> Thanks,
>>>
>>> Pierre
>>>
>>>
>>>
>>

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