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Tue, 28 Jul 2026 00:54:19 +0000 (GMT) Received: from [9.61.152.139] (unknown [9.61.152.139]) by smtpav06.wdc07v.mail.ibm.com (Postfix) with ESMTP; Tue, 28 Jul 2026 00:54:19 +0000 (GMT) Message-ID: <59a72d98-5f33-4bda-88cd-4e89ba237b9a@linux.ibm.com> Date: Mon, 27 Jul 2026 20:54:18 -0400 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 08/10] s390/vfio_ccw: move cp cleanup out of not operational To: Matthew Rosato , linux-s390@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Halil Pasic , Christian Borntraeger , stable@vger.kernel.org References: <20260727192230.2715207-1-farman@linux.ibm.com> <20260727192230.2715207-9-farman@linux.ibm.com> <1819d316-62b9-48c7-abaa-f40681e22abf@linux.ibm.com> Content-Language: en-US From: Eric Farman Autocrypt: addr=farman@linux.ibm.com; keydata= xsFNBF7EiEwBEADGG0EtNKnjp+kQfEVqlqxXoBHjnaQptFpMgxNlz2GtqOujY6nzEWnybIXY 63XUTmMS/tWUf2DTbNCNoWwumGM/I2Gj1uGyMnc4Q477BQlL/e2/9MRaut11rwHsi4zmWylc jO0eFTSLFA8yFBj9osT3uZzk5TwWkD8sf+rD916fFVk0G39uYEd5sjEzjeOf9/dwXyZpjJY6 api1pUHEw7weRvOnllJAfIKFz+KoR6d7ezvMF9zOYHF73FGeSVIYoIEUhA5Cdg60rSlTtHb2 cftex3/cEapvY5bK3CKJ33BVVK10Bht9XfVaA/AOcg/3o5ZbhSIwz4xScGsEVf/Yr368YMdr 3VkCZrmN2ppmVRz/RvAmCyItnmzoVDlSREA6Faw6S0x8Oi7lN0cKh2hy9VPcVupraXJZrdAh GtdU+jrJvSbpdsrX8F7K3RwynbiqGrqC0izGla04hhtei/uwthatglukuxep4PknDGbzijg8 Ef7A8t3qEVklUDrsnNPN5HbR9QQdeF0HuWsDTfILbZv1MICfOK3BCDeT5mJWaJCoQ2rbuljM e1hFSt+mr7GV4h6NcBE+uGIqDSzQORtyTo0uBV4et3cSE84JxOfXBMrj0TlL1855JaIoPWEN uhDRB/dHW8+Fumq2du5hLcaXPka+MO26cNVKVLF0/JjwMTZ9bQARAQABzSJFcmljIEZhcm1h biA8ZmFybWFuQGxpbnV4LmlibS5jb20+wsGuBBMBCABYAhsDBwsJCAcDAgEGFQgCCQoLBBYC AwECHgECF4AdGGh0dHBzOi8va2V5c2VydmVyLnVidW50dS5jb20WIQTSxgUEyej1aM/lh7U4 J7IScb+VYgUCYel8TgAKCRA4J7IScb+VYsHAD/9BSQj7HeJf90PttOmVh35Bb4QyHLZ4g+9x waM59JCKGbiURuNRIGnoRarYXHk6vfy19v8v56Dy1IOlKWaRnizp5Mw9zXBBTCs4fgNbOzY/ SggFY2UzcziXDG29X9zznq5LgY1Jf/cwm1O+rn89GKCZWZhLEB2wKzBj7hum7NBdW+lxfVwp 2qONGDerttWDwAHxJ995k9aDJahq9kIKEMEZbrTQ8JI8KZGoox6+HA04EhoNzxvbV0J+/gLJ 2DkvxN5/xmcD3z+s8B5ev3NarOF17AIA9oCdfu8CPAupcNqJW86m19P5q6AyRB2ZLyAIAAhr HCXrnlh/8HJW1yCOVXxprFdpg1SX1fuArjbFAh53vVVDfkZlwHeTeE7+3y1rtDLfy830pqdD ymv94yey2y1+iZBdbaW0fSC/JkjkOCy8oZawkH3geM4MXV4ze4gbBH6BhxW/0gbEYjnLm3FA 53JcXwhHQFPWIYEYYPvATJi0JUiMY1Znkm3QBWDOCXSrG0tHpAclBa9L40zLRwA1h9YOMFEs qvKijUdvcDf4sTdJ+A6YL66grzul5vNt06NlqsI8HUDHE6vghqyWxupCav2+9b1BuLie++er b8OCo5n3TUHsVMjYJEePU1EkcCa84dCm+CXqPthgRv0sbe4UQEd/qUoVMdWj7Q7FL96mBn0G zM7BTQRexIhMARAAp+k1sC4y7Wtwjqtfu9wIihvY/Vot0v/sKg8CRGRIIRGLiCeA9o+2ZlxC jYztT3Leri5Vo5z09OmRMvoFLJjcHMCG5sYeZwOWNAbeuAxGkIMDSB4pLl3t2c+1PQuMBCd7 +mRZFaMEJfT3nhdUKxy2rp1+YucnA67xGXUJCiD5l9UmhPqa7SAYlpMAqDz7cmBo25c/UNm1 Tpwjrh70jq/4guV5gnprawH8nkRjdKH1JvKWvkuaB7FNZ9IuSHlWclcQX4IQMsaxsU2emAbP VYv7l4YNlKfdlJd8tuEodjuMLOBnr7e9H0hVNUWGFN9bkBNRu3zi/jvhyu15Iu4euR/WdVNu 2K2iYxIfiGMnv0F/a6R1bm10lCJrjyf23J8DYIeH4YmHvOOqYFkq3DWOctlXbb3+aABqjYt3 mkiOLXeplqbo/m3rWcGNd8Q/d1aVA0wm5+Nt3RdSuXG2FHOFdVUQKPLpf1NUH/LInBhS/9Ys ajm6tWXKv7hxwWmyz0u/th6gUra3KpARB1ypebWHULLNzKGwVS81XNs76QhXwX04cyiwLqKb WqLqJKThz+rLa09Ap+eO/UzPfFXvWYWfTeFRIQ/tKF332ZzRR8Xrh/fk//YXyRfpoE/7i5uz ve0HZWp5jXg9Yb+S6g0+XUKznnN9B8WLLCcuRIuSa722070v7KsAEQEAAcLBdgQYAQgAIAIb DBYhBNLGBQTJ6PVoz+WHtTgnshJxv5ViBQJh6XwwAAoJEDgnshJxv5Vib28P/1BYT5gvjuEB A80AXo/IqycicXxDJtrfmyw4COP7bi7AuiDcKyA1wRzC51paKwPFB8Unk2GvG4DV6aDmGTJY +GeCYgthQ+znW461S8B6GqDCAQt2VDNNFVU+gTuh7vYQOgt/OjtiiAvMIJBVRbXoNSRokKOF tpTiXf3ZOsAkot5ZmxE0TV94v18sp/bC84YvFyaxpw5bilT7bmpcq8B8/3yb0kmy6gXLcQAp OnomV3sQBmm050amiO3tvxMNv8J71AvNdTG/rojTDKUl2Nw4f+aw4nVw874m2XpEe9JGRw54 5d2dN8k3GpzcTBe9fCQPOFHOGkQ1CgptDkQuQVD3DIeNzQjXf6xehEymIKnLOkukT2smV0zh fj08z7eiv+dsmnBsbhdM6DKU8qIgkTu77TfHUKjjOY/Mj0YHPuH/J4b1AZFxBhGP0BTKiB2W CR6/49XVKvY1jHxgadSSNCD+f7tEqUNBlVl+P0emMJaYpK1+gy88ma4g3nvyOVe/VzDPjGDC 4HX/6RAR4Dbzry6/epWTTji+7ApzePzmJzPcuzD31ICsgT2dJ6ydxyxxXikBFJqx6BPOF+u+ 1BtKcTz1ek3I2sWvBM1V5CKaFw7iNXxS6HgS2scuAT2awKq+BQlt778/GfBWpXonfqixMvit y8m0x6unNti2MZIUMy0m2gcE In-Reply-To: <1819d316-62b9-48c7-abaa-f40681e22abf@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: tcubRgWp0vv7cFjJXpbVQgVLznZHO3zt X-Proofpoint-ORIG-GUID: tcubRgWp0vv7cFjJXpbVQgVLznZHO3zt X-Proofpoint-Spam-Info: AW1haW4tMjYwNzI4MDAwNCBTYWx0ZWRfXxRkoTtoZ0iam luO6iqZmbruGlkR7IXcc/lyfgmvMIoTzobRZj0JWbtcD58PuOM0R/fetvVPTRYmN0xalZbsB+MQ /2+4kI5uVTr0SLxXKbFH0c+ABhmOzLA= X-Authority-Analysis: v=2.4 cv=dYuwG3Xe c=1 sm=1 tr=0 ts=6a67fdbe cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=IkcTkHD0fZMA:10 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=BDJVAYCkDSfPSt_zWL4A:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzI4MDAwNCBTYWx0ZWRfXxelnmyzUZOSI zJtKgixD3HqaVmTv1gK2UJng8IFjYGLtUufdnVDPQ4XmODLLZek/AiJ882yLkltTSNiO09rsAdj OKtTIpRjKG5ZMLDurqmgTNt+WfyH8xMTUKObAlV1ezP43r8WQo1o6Te3T1GydOLmEaMFJXbs0kS E+dGbwQM234OdwGj+CvLzZ8qxVK2RUhIaqz10gE0zk1yPQhIZ4Kva4gWDG849iE8O6ZWMb52AMD GqbnR9wL6FPsKirICxl0Jk6rh2d3HIxD3fLPA0Hnq5x0lXMos5HRAFrE1ZdMCaDqO9Z7quuM3sD adx3N58rf8rw4yXS65gPmKLhyeMInv1LpMsa+5GIjmelujUBZJTeFdiT3cHms98K20D/GCP47/W RyyYxT/7eRRD6LynYL5k3GWmmbIxBEzK+D0uj5Oprx77+K+c7kR85ZVPDaE2Jssh/4x3WLElWpG 7l6vsizJYkf04L0SZ4w== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-07-27_07,2026-07-27_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 impostorscore=0 clxscore=1015 phishscore=0 malwarescore=0 spamscore=0 lowpriorityscore=0 bulkscore=0 suspectscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607280004 On 7/27/26 5:54 PM, Matthew Rosato wrote: > On 7/27/26 3:22 PM, Eric Farman wrote: >> The fsm_notoper() routine is called when the device has been >> lost, and is (by definition) no longer operational. Since this >> can happen asynchronously from the normal behavior of the >> driver, the cleanup may happen when holding other locks >> in the calling sequence (notably, the cio subchannel lock). >> >> Push the cleanup of the private->cp resources to a workqueue, >> where it can be done out from under that lock sequence and >> (soon) under its own serialization mechanism. > > This part of the commit message needs updating now that you are not > introducing a cp_mutex. > >> >> Fixes: 204b394a23ad ("vfio/ccw: Move FSM open/close to MDEV open/close") >> Cc: stable@vger.kernel.org >> Signed-off-by: Eric Farman >> --- >> drivers/s390/cio/vfio_ccw_drv.c | 9 +++++++++ >> drivers/s390/cio/vfio_ccw_fsm.c | 3 +-- >> drivers/s390/cio/vfio_ccw_ops.c | 3 +++ >> drivers/s390/cio/vfio_ccw_private.h | 3 +++ >> 4 files changed, 16 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c >> index 1a095085bc72..c197ad5ab580 100644 >> --- a/drivers/s390/cio/vfio_ccw_drv.c >> +++ b/drivers/s390/cio/vfio_ccw_drv.c >> @@ -125,6 +125,15 @@ void vfio_ccw_crw_todo(struct work_struct *work) >> eventfd_signal(private->crw_trigger); >> } >> >> +void vfio_ccw_notoper_todo(struct work_struct *work) >> +{ >> + struct vfio_ccw_private *private; >> + >> + private = container_of(work, struct vfio_ccw_private, notoper_work); >> + >> + cp_free(&private->cp); >> +} >> + >> /* >> * Css driver callbacks >> */ >> diff --git a/drivers/s390/cio/vfio_ccw_fsm.c b/drivers/s390/cio/vfio_ccw_fsm.c >> index 4d7988ea47ef..4d47a3c7b9a0 100644 >> --- a/drivers/s390/cio/vfio_ccw_fsm.c >> +++ b/drivers/s390/cio/vfio_ccw_fsm.c >> @@ -170,8 +170,7 @@ static void fsm_notoper(struct vfio_ccw_private *private, >> css_sched_sch_todo(sch, SCH_TODO_UNREG); >> private->state = VFIO_CCW_STATE_NOT_OPER; >> >> - /* This is usually handled during CLOSE event */ >> - cp_free(&private->cp); >> + queue_work(vfio_ccw_work_q, &private->notoper_work); >> } >> >> /* >> diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c >> index bd488e40e153..8ec6b175d991 100644 >> --- a/drivers/s390/cio/vfio_ccw_ops.c >> +++ b/drivers/s390/cio/vfio_ccw_ops.c >> @@ -54,6 +54,7 @@ static int vfio_ccw_mdev_init_dev(struct vfio_device *vdev) >> INIT_LIST_HEAD(&private->crw); >> INIT_WORK(&private->io_work, vfio_ccw_sch_io_todo); >> INIT_WORK(&private->crw_work, vfio_ccw_crw_todo); >> + INIT_WORK(&private->notoper_work, vfio_ccw_notoper_todo); >> >> private->cp.guest_cp = kzalloc_objs(struct ccw1, CCWCHAIN_LEN_MAX); >> if (!private->cp.guest_cp) >> @@ -139,6 +140,7 @@ static void vfio_ccw_mdev_release_dev(struct vfio_device *vdev) >> /* Should be empty, but just in case */ >> cancel_work_sync(&private->io_work); >> cancel_work_sync(&private->crw_work); >> + cancel_work_sync(&private->notoper_work); > > Sashiko mentions (and I agree) that you can accidentally leak the cp > resources if you manage to cancel the pending notoper_work before it runs. > > Since you are not running on a workqueue thread, it should be OK to > flush instead to make sure that the pending item is executed. > > A subsequent cancel should not be necessary, since we know that only 1 > instance of vfio_ccw_notoper_todo() will ever be queued because we queue > it on the first time the device goes NOT_OPER. Based on the FSM, once > the device goes NOT_OPER, subsequent transitions into NOT_OPER are > treated as a NOP and there is no way to transition to a different state > other than NOT_OPER until the device is released, so you can't go from > NOT_OPER->x->NOT_OPER. Agreed, this should be flush not cancel. Though, the piece where that's important is the call in close_dev, which is the counterpart to the open_device path which allows a cp to be queued in the first place. A close will have preceded a release, which means there will no longer be any cp's outstanding, and userspace will have been unable to submit new ones without performing another open. The other two elements (io_work and crw_work) would be queued in response to a hardware event (an interrupt and a CRW, respectively), which could come asynchronously from all of this, so needs to be in both close and release. > > Would probably be good to include a (less verbose) comment to that > effect along with the flush. > Agreed; thanks. >> >> kmem_cache_free(vfio_ccw_crw_region, private->crw_region); >> kmem_cache_free(vfio_ccw_schib_region, private->schib_region); >> @@ -209,6 +211,7 @@ static void vfio_ccw_mdev_close_device(struct vfio_device *vdev) >> >> cancel_work_sync(&private->io_work); >> cancel_work_sync(&private->crw_work); >> + cancel_work_sync(&private->notoper_work); >> >> vfio_ccw_unregister_dev_regions(private); >> } >> diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h >> index 0501d4bbcdbd..e2256402b089 100644 >> --- a/drivers/s390/cio/vfio_ccw_private.h >> +++ b/drivers/s390/cio/vfio_ccw_private.h >> @@ -102,6 +102,7 @@ struct vfio_ccw_parent { >> * @req_trigger: eventfd ctx for signaling userspace to return device >> * @io_work: work for deferral process of I/O handling >> * @crw_work: work for deferral process of CRW handling >> + * @notoper_work: work for deferred processing in not-operational state >> */ >> struct vfio_ccw_private { >> struct vfio_device vdev; >> @@ -125,11 +126,13 @@ struct vfio_ccw_private { >> struct eventfd_ctx *req_trigger; >> struct work_struct io_work; >> struct work_struct crw_work; >> + struct work_struct notoper_work; >> } __aligned(8); >> >> int vfio_ccw_sch_quiesce(struct subchannel *sch); >> void vfio_ccw_sch_io_todo(struct work_struct *work); >> void vfio_ccw_crw_todo(struct work_struct *work); >> +void vfio_ccw_notoper_todo(struct work_struct *work); >> >> extern struct mdev_driver vfio_ccw_mdev_driver; >> >