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Tue, 5 May 2026 20:08:45 +0000 (GMT) Received: from [9.111.63.144] (unknown [9.111.63.144]) by smtpav04.dal12v.mail.ibm.com (Postfix) with ESMTP; Tue, 5 May 2026 20:08:44 +0000 (GMT) Message-ID: <5d3ab0fc1893c145b320e532db309b0f18bfa98c.camel@linux.ibm.com> Subject: Re: [PATCH v1 1/3] s390/pci: Preserve FMB state in device re-enablement From: Niklas Schnelle To: Omar Elghoul , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, mjrosato@linux.ibm.com, alifm@linux.ibm.com, farman@linux.ibm.com, gbayer@linux.ibm.com, alex@shazbot.org In-Reply-To: <642e1e814aa8050ea2bb21fa2e5b10b83145ba43.camel@linux.ibm.com> References: <20260501192530.9429-1-oelghoul@linux.ibm.com> <20260501192530.9429-2-oelghoul@linux.ibm.com> <65433c0e240b72ddf731dbc27a9503f1d11ad0b8.camel@linux.ibm.com> <642e1e814aa8050ea2bb21fa2e5b10b83145ba43.camel@linux.ibm.com> Autocrypt: addr=schnelle@linux.ibm.com; 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charset="UTF-8" Content-Transfer-Encoding: quoted-printable Date: Tue, 05 May 2026 22:07:43 +0200 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Evolution 3.58.3 (3.58.3-1.fc43) X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTA1MDE5NSBTYWx0ZWRfXys9h+dZpl9Gj TPUqgBS7aDc66syoh3g8AJRC0DQCfvH6bXaXslR7c2ecg46lFDgLm2Agt+r3kq9j5rBHkn8P+eh 4ioEh6FlANxQsB2+UhZIJeX/sUVQ4pTxM0ns16QX7d7idFud2Ru/lGch2GwI92Q27Kg70l19RS7 gOQTIV1rSdY+mncUdl1hBBVmgApMeOVkEZxk6jV84MXacHZC7uG8e+oPEqeO1iStdi0EJMvzVQ8 mNnqFZlQ3wELD1ghm78a9RQoOz5iCQulng74pGdbZ3lyQU2/oGo3ccnIPjnjBfcwFL3zLbqSVSR 0HWv/XavJQPDRkzh1TExWGdWQwwXbhxdoeKMGqFIwaey9aVgiCItIcouHfiuh1VYMetl/3QmHfD Ai3TTMKYI7AmvKqlivZuNGcrSG0GSvJY0dCDA7L9EWcOwhkGtUyfFJlrZvyAkELLAHw6vC1yac8 +1BIXkj35jgX4gBebnA== X-Proofpoint-ORIG-GUID: feAHh4S-0EC-naZdkdoa2tSnp8t2PRgQ X-Proofpoint-GUID: feAHh4S-0EC-naZdkdoa2tSnp8t2PRgQ X-Authority-Analysis: v=2.4 cv=ctWrVV4i c=1 sm=1 tr=0 ts=69fa4e51 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=NGcC8JguVDcA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=VnNF1IyMAAAA:8 a=AgMhM9oai4GQE_Iv-gEA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-05-05_02,2026-04-30_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 lowpriorityscore=0 adultscore=0 clxscore=1015 suspectscore=0 impostorscore=0 spamscore=0 malwarescore=0 phishscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604200000 definitions=main-2605050195 On Tue, 2026-05-05 at 17:48 +0200, Niklas Schnelle wrote: > On Tue, 2026-05-05 at 17:41 +0200, Niklas Schnelle wrote: > > On Fri, 2026-05-01 at 15:25 -0400, Omar Elghoul wrote: > > > Introduce a function zpci_fmb_reenable_device() that checks for the s= tate > > > of the FMB and reuses the same buffer where appropriate. If FMB was n= ot > > > previously enabled, it enables it for the device. Call this function = during > > > a zPCI device re-enablement, which in turn implicitly ensures that th= e FMB > > > is enabled for host devices during their KVM registration. > > >=20 > > > This function also clears out the software counters, so that a progra= m > > > resetting an FMB would see all its counters restart from zero as expe= cted. > > > The function to clear the software counters is also separated into a = static > > > function as it is now reused in both zpci_fmb_enable_device() and > > > zpci_fmb_reenable_device(). > > >=20 > > > Signed-off-by: Omar Elghoul > > > --- > > > arch/s390/include/asm/pci.h | 1 + > > > arch/s390/pci/pci.c | 71 ++++++++++++++++++++++++++++++-----= -- > > > 2 files changed, 59 insertions(+), 13 deletions(-) > > >=20 > >=20 > > Looks good to me. I also gave this a quick sniff test on an LPAR but > > still have to test with the FMB handling for KVM that this enabled so > > not enough for a Tested-by yet. > >=20 > > Still feel free to add my: > >=20 > > Reviewed-by: Niklas Schnelle > >=20 > > Thanks, > > Niklas >=20 > Ah, missed one thing, the kernel-test-robot is of course right in that > with this patch flags and ctrs are now unused in > zpci_fmb_enable_device() so the declarations should be dropped. The > same is also true in zpci_fmb_reenable_device() which the test robot > did miss! >=20 > Thanks, > Niklas Missed another issue which thankfully Sashiko found. The use of zpci_fmb_reenable_device() in zpci_reenable_device() leads to the new call chain: recover_store() _do_recover() zpci_reenable_device() zpci_fmb_reenable_device() Where we don't take the zdev->fmb_lock. I think it makes sense to add a lockdep_assert_held() to zpci_fmb_reenable_device(). Thanks, Niklas