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Thu, 17 Sep 2026 02:21:18 +0000 (GMT) Received: from [9.61.177.109] (unknown [9.61.177.109]) by smtpav04.wdc07v.mail.ibm.com (Postfix) with ESMTP; Thu, 17 Sep 2026 02:21:18 +0000 (GMT) Message-ID: <099b4e3f-4156-42e4-a2e9-bdc715547bef@linux.ibm.com> Date: Wed, 16 Sep 2026 22:21:17 -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: 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, 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> From: Matthew Rosato Content-Language: en-US In-Reply-To: <20260916213222.233-3-oelghoul@linux.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTE3MDAyNSBTYWx0ZWRfX4xMa4EzfOqL8 Sszk4JP1sAw7Qzt1mt1r4t3+895XLHbe8Q6SumC/wHaFQWcoHHj3Tma28cLJI7GCn8wv0N0P7bz /AddAw+D7OQ7OQ6dHIq5RdYaunHQ8vZZYc1FiO6LFiAXDUj5gU3LayorRkvPL/VNL2V0mxKblln 0rJsZ14BOqOQMslfHVO9uNtdTnxNEaVRYr4MJM8KfwRfxgdPUdhS6EVChVHxW8CUDMkijf5jMe1 Typ4dozH1Xt92nKS/l0K/LWa8cY6AuU/E+Fk1C1w5Nhbp5vLsWfEJP96mIsVGoQWBjHoAf5bKLl 5UXM+2NQq4+R3ACb3tSyF/wcMTzxzyfJs6AEvBc2Aeui0FrnC1YIC0O+OtAFou1vgKyxzcE3hV0 b6AZrgcjbtDVtCMXrS6E9Tp/P+1GIS60fujVYoZ+2yIG89gGZqr1ISIA9V6r54IlyipK033uRa9 mb/OLtu998gA9e61ogA== X-Proofpoint-Spam-Info: AW1haW4tMjYwOTE3MDAyNSBTYWx0ZWRfXwU9C5HCp5gx4 5OjbauRbGk0N+PTH7ZafpGnFN+D1ASUkQRdVxWHhtmntQiRTtV1D4zedSUJ2/NWZF06UiKiZQlB 9h/cWTNCrz26whFaO9vQN3CBD+tlT58= X-Authority-Analysis: v=2.4 cv=Zsx4uN7G c=1 sm=1 tr=0 ts=6aab4ea1 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=XNYn6gUGNGRw0UYtJOQA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-ORIG-GUID: FF4LZ6b1qdqu5GRHEenFk2-DIeJ0U5Zc X-Proofpoint-GUID: FF4LZ6b1qdqu5GRHEenFk2-DIeJ0U5Zc 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=2026-09-16_03,2026-09-16_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 impostorscore=0 clxscore=1015 priorityscore=1501 lowpriorityscore=0 bulkscore=0 adultscore=0 phishscore=0 spamscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609170025 > +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. 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);