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Fri, 3 Apr 2026 17:19:59 +0000 (GMT) Message-ID: Date: Fri, 3 Apr 2026 10:19:59 -0700 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 2/2] PCI: s390: Expose the UID as an arch specific PCI slot attribute To: Niklas Schnelle , Bjorn Helgaas , Jonathan Corbet , Lukas Wunner , Shuah Khan Cc: Alexander Gordeev , Christian Borntraeger , Gerald Schaefer , Gerd Bayer , Heiko Carstens , Julian Ruess , Matthew Rosato , Peter Oberparleiter , Ramesh Errabolu , Sven Schnelle , Vasily Gorbik , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linux-s390@vger.kernel.org References: <20260402-uid_slot-v6-0-d5ea0a14ddb9@linux.ibm.com> <20260402-uid_slot-v6-2-d5ea0a14ddb9@linux.ibm.com> Content-Language: en-US From: Farhan Ali In-Reply-To: <20260402-uid_slot-v6-2-d5ea0a14ddb9@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=J6enLQnS c=1 sm=1 tr=0 ts=69cff6c4 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=IkcTkHD0fZMA:10 a=A5OVakUREuEA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=zab_MO1Yg7CTISiwoJcA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDAzMDE1NCBTYWx0ZWRfX5LQFWOEzEKoj sv9QIsXSkhcl9+YSN1NNR1mene1qjziSaxZZ7/4Demu9AojEBiEEqbpoN/+vBWJtNciwqFwdV8X S2taKkVsx23y7yoUAemgnncRAMTZ4AkBgXCAxFRtwHDYjdLc7Ck69Ig4dLHdWonOMmvhvO6o4jL Qz7D2Qcfh0Oboe8aAnvJMQ813JQj8EUrL6BWneN+g/Lzmol/QzMFqZFbno+SEopEPCJqo3Qo175 wyEzciK4c8xxqWaVyJ/zBsPYfuKezqdqN8t36AJRQeLmtSSOaUWzQEL6647lzF3+5sCQSGIPK67 NPnm4EpKLqzVCG1xlkeRL+Tn8HdLPg5grbzWcn5aTlonnGwYxp61fdCz+6GAEKH7N+2nTL9v4q9 cNobk3epuDFDBkPEkybq0zm2woqh1vroasReDwy4vRQlK5xHyZgKW7KkTcHZ4zoOXcPWTsvBi8Y pZ0jsI13F1tS6CuRj/A== X-Proofpoint-GUID: ttKxjis-mUI1CHId1Ow0JEo2NRbZ3Qse X-Proofpoint-ORIG-GUID: 7HTSU5BayCQorpXQvpwkBPttdMaWSRRL 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=2026-04-03_05,2026-04-03_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 clxscore=1015 adultscore=0 priorityscore=1501 bulkscore=0 phishscore=0 malwarescore=0 lowpriorityscore=0 spamscore=0 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2604030154 On 4/2/2026 1:34 PM, Niklas Schnelle wrote: > On s390, an individual PCI function can generally be identified by two > identifiers, the FID and the UID. Which identifier is used depends on > the scope and the platform configuration. > > The first identifier, the FID, is always available and identifies a PCI > device uniquely within a machine. The FID may be virtualized by > hypervisors, but on the LPAR level, the machine scope makes it > impossible to create the same configuration based on FIDs on two > different LPARs of the same machine, and difficult to reuse across > machines. > > Such matching LPAR configurations are useful, though, allowing > standardized setups and booting a Linux installation on different LPARs. > To this end the UID, or user-defined identifier, was introduced. While > it is only guaranteed to be unique within an LPAR and only if indicated > by firmware, it allows users to replicate PCI device setups. > > On s390, which uses a machine hypervisor, a per PCI function hotplug > model is used. The shortcoming with the UID then is, that it is not > visible to the user without first attaching the PCI function and > accessing the "uid" device attribute. The FID, on the other hand, is > used as the slot name and is thus known even with the PCI function in > standby. > > Remedy this shortcoming by providing the UID as an attribute on the slot > allowing the user to identify a PCI function based on the UID without > having to first attach it. Do this via a macro mechanism analogous to > what was introduced by commit 265baca69a07 ("s390/pci: Stop usurping > pdev->dev.groups") for the PCI device attributes. > > Reviewed-by: Gerd Bayer > Reviewed-by: Julian Ruess > Signed-off-by: Niklas Schnelle > --- > Documentation/arch/s390/pci.rst | 7 +++++++ > arch/s390/include/asm/pci.h | 4 ++++ > arch/s390/pci/pci_sysfs.c | 20 ++++++++++++++++++++ > drivers/pci/slot.c | 13 ++++++++++++- > 4 files changed, 43 insertions(+), 1 deletion(-) > > diff --git a/Documentation/arch/s390/pci.rst b/Documentation/arch/s390/pci.rst > index 31c24ed5506f1fc07f89821f67a814118514f441..4c0f35c8a5588eee3cf0d596e0057f24b3ed079c 100644 > --- a/Documentation/arch/s390/pci.rst > +++ b/Documentation/arch/s390/pci.rst > @@ -57,6 +57,13 @@ Entries specific to zPCI functions and entries that hold zPCI information. > > - /sys/bus/pci/slots/XXXXXXXX/power > > + In addition to using the FID as the name of the slot the slot directory > + also contains the following s390 specific slot attributes. > + > + - uid: > + The User-defined identifier (UID) of the function which may be configured > + by this slot. See also the corresponding attribute of the device. > + > A physical function that currently supports a virtual function cannot be > powered off until all virtual functions are removed with: > echo 0 > /sys/bus/pci/devices/DDDD:BB:dd.f/sriov_numvf > diff --git a/arch/s390/include/asm/pci.h b/arch/s390/include/asm/pci.h > index c0ff19dab5807c7e1aabb48a0e9436aac45ec97d..5dcf35f0f325f5f44b28109a1c8d9aef18401035 100644 > --- a/arch/s390/include/asm/pci.h > +++ b/arch/s390/include/asm/pci.h > @@ -208,6 +208,10 @@ extern const struct attribute_group zpci_ident_attr_group; > &pfip_attr_group, \ > &zpci_ident_attr_group, > > +extern const struct attribute_group zpci_slot_attr_group; > + > +#define ARCH_PCI_SLOT_GROUPS (&zpci_slot_attr_group) > + > extern unsigned int s390_pci_force_floating __initdata; > extern unsigned int s390_pci_no_rid; > > diff --git a/arch/s390/pci/pci_sysfs.c b/arch/s390/pci/pci_sysfs.c > index c2444a23e26c4218832bb91930b5f0ffd498d28f..d98d97df792adb3c7e415a8d374cc2f3a65fbb52 100644 > --- a/arch/s390/pci/pci_sysfs.c > +++ b/arch/s390/pci/pci_sysfs.c > @@ -187,6 +187,17 @@ static ssize_t index_show(struct device *dev, > } > static DEVICE_ATTR_RO(index); > > +static ssize_t zpci_uid_slot_show(struct pci_slot *slot, char *buf) > +{ > + struct zpci_dev *zdev = container_of(slot->hotplug, struct zpci_dev, > + hotplug_slot); > + > + return sysfs_emit(buf, "0x%x\n", zdev->uid); > +} I think the way we assign the same pci slot to multifunctions (PF and VF on the same LPAR), IIUC we could possibly display the wrong uid here. I am hoping my patch [1] can fix this. I am curious, is there any s390-tool that would use the uid? Though this would only impact the NETD devices on newer machines, so I don't know if we want to gate this behind my patch? [1] https://lore.kernel.org/all/20260330174011.1161-2-alifm@linux.ibm.com/ Thanks Farhan > + > +static struct pci_slot_attribute zpci_slot_attr_uid = > + __ATTR(uid, 0444, zpci_uid_slot_show, NULL); > + > static umode_t zpci_index_is_visible(struct kobject *kobj, > struct attribute *attr, int n) > { > @@ -243,6 +254,15 @@ const struct attribute_group pfip_attr_group = { > .attrs = pfip_attrs, > }; > > +static struct attribute *zpci_slot_attrs[] = { > + &zpci_slot_attr_uid.attr, > + NULL, > +}; > + > +const struct attribute_group zpci_slot_attr_group = { > + .attrs = zpci_slot_attrs, > +}; > + > static struct attribute *clp_fw_attrs[] = { > &uid_checking_attr.attr, > NULL, > diff --git a/drivers/pci/slot.c b/drivers/pci/slot.c > index 787311614e5b6ebb39e7284f9b9f205a0a684d6d..2f8fcfbbec24e73d0bb6e40fd04c05a94f518045 100644 > --- a/drivers/pci/slot.c > +++ b/drivers/pci/slot.c > @@ -96,7 +96,18 @@ static struct attribute *pci_slot_default_attrs[] = { > &pci_slot_attr_cur_speed.attr, > NULL, > }; > -ATTRIBUTE_GROUPS(pci_slot_default); > + > +static const struct attribute_group pci_slot_default_group = { > + .attrs = pci_slot_default_attrs, > +}; > + > +static const struct attribute_group *pci_slot_default_groups[] = { > + &pci_slot_default_group, > +#ifdef ARCH_PCI_SLOT_GROUPS > + ARCH_PCI_SLOT_GROUPS, > +#endif > + NULL, > +}; > > static const struct kobj_type pci_slot_ktype = { > .sysfs_ops = &pci_slot_sysfs_ops, >