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Thu, 17 Sep 2026 13:32:47 +0000 (GMT) Received: from [9.61.247.238] (unknown [9.61.247.238]) by smtpav01.wdc07v.mail.ibm.com (Postfix) with ESMTPS; Thu, 17 Sep 2026 13:32:46 +0000 (GMT) Message-ID: <85cb647d-b1c8-4804-b206-2cae1e03e20d@linux.ibm.com> Date: Thu, 17 Sep 2026 09:32:46 -0400 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 2/4] s390/pci: Reuse FMB buffer and preserve state in device re-enablement To: Matthew Rosato , 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, schnelle@linux.ibm.com, alifm@linux.ibm.com, farman@linux.ibm.com, gbayer@linux.ibm.com, pasic@linux.ibm.com, alex@shazbot.org References: <20260916213222.233-1-oelghoul@linux.ibm.com> <20260916213222.233-3-oelghoul@linux.ibm.com> <099b4e3f-4156-42e4-a2e9-bdc715547bef@linux.ibm.com> Content-Language: en-US From: Omar Elghoul In-Reply-To: <099b4e3f-4156-42e4-a2e9-bdc715547bef@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTE3MDE5MCBTYWx0ZWRfXx/upzehTN8Yr Cwn+G3lelFZilDPvTW5woglDWoDvLeTEYtQr+W+TwI/bACAe9PpQ02oVA9rMWPlt6FRRoul/LDE F8ikLriu3lpubOn+Q21ZYW1FVBeMHVfnoJAqcE+KyQYkb/hnYPds3LvK1Zkrd6XbASY8+Aa2K6F uD1LbDqswBlkrysIZruKvytIrBSLJ5+zBAw2qQArramqSbjyHrbnOVprKoXh8zhIUz27zdJUSJs ropyp9fZtBQZjOnd8brVlNuYzGPeF0iRNEfnN1ErreIzno7biNBwTRjLdygQq8OoYJcLp23xB6s f8OcFA/PbchUl4QS4/uoFAJfF+exY3ShUJHs5Mdl/rlEIa5oBkJIT4wzwKykIXaGVRY9H7Qqp2r ZIODJzAUwWaI8niGOJ9tVJ1KG7opOa9LQLqmFuXswlMCyHdHfTjFGBnlL889kMkEPiu5CEUowPX 21SAz5m5I3ZQEUeMk9A== X-Proofpoint-GUID: eqokwp51adjx54htjj43JQ1sPjUCIxO4 X-Authority-Analysis: v=2.4 cv=DobDa2/+ c=1 sm=1 tr=0 ts=6aabec03 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=EUQsns2teDQkhDBnVLYA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-ORIG-GUID: eqokwp51adjx54htjj43JQ1sPjUCIxO4 X-Proofpoint-Spam-Info: AW1haW4tMjYwOTE3MDE5MCBTYWx0ZWRfX8dZRNK2XIQZz Qv5ldF9ifEFyPcmAhKsUI5SpapQ7TQEHchVe8svr4n8flUALBr6UsVAOV5U+O2oaRtCqtCPnKUv xWYR1IPuXo4mZ3etzAR4o1ROAALhNaU= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-09-17_02,2026-09-16_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 malwarescore=0 priorityscore=1501 suspectscore=0 impostorscore=0 spamscore=0 clxscore=1015 adultscore=0 bulkscore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609170190 On 9/16/26 10:21 PM, Matthew Rosato wrote: > >> +int zpci_fmb_reenable_device(struct zpci_dev *zdev) >> +{ >> + u64 req = ZPCI_CREATE_REQ(zdev->fh, 0, ZPCI_MOD_FC_SET_MEASURE); >> + struct zpci_fib fib = {0}; >> + u8 cc, status; >> + >> + lockdep_assert_held(&zdev->fmb_lock); >> + >> + if (!zdev->fmb_enabled) >> + return zpci_fmb_enable_device(zdev); > > Sashiko has a point here, won't all paths that call zpci_reenable_device > now unconditionally turn on FMB here even if it was purposely disabled? > > The pattern of callers for zpci_reenable_device() is: > > zpci_disable_device() > ... > zpci_reenable_device() > > We only care to re-enable the FMB during device re-enable if the device > had FMB enabled at the time zpci_disable_device() was called. The way I thought of it was pcibios_enable_device() already enables measurement, so we might as well ensure it is enabled when the zdev is re-enabled. That default state is also helpful for the later patches because kvm_s390_pci_register_kvm() calls zpci_reenable_device(). But I guess if we didn't want to conflate the two, we could also add an unconditional zpci_fmb_reenable_device() within the KVM register hook, to run after the zpci_reenable_device(), whichever you'd prefer. Thanks > > Thanks, > Matt > >> + >> + fib.gd = zdev->gisa; >> + cc = zpci_mod_fc(req, &fib, &status); /* Disable function measurement */ >> + >> + /* Unlike in zpci_fmb_disable_device(), cc == 3 is not a valid state here >> + * because we are re-enabling function measurement for the same function >> + * handle. >> + */ >> + if (cc) >> + return -EIO; >> + >> + zdev->fmb_enabled = 0; >> + return zpci_fmb_enable_device(zdev); >> +} >> +EXPORT_SYMBOL_GPL(zpci_fmb_reenable_device); >