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Thu, 23 Oct 2025 15:20:53 GMT Received: from smtpav06.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1A8D858055; Thu, 23 Oct 2025 15:20:53 +0000 (GMT) Received: from smtpav06.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 94F9358043; Thu, 23 Oct 2025 15:20:50 +0000 (GMT) Received: from tuxmaker.boeblingen.de.ibm.com (unknown [9.152.85.9]) by smtpav06.dal12v.mail.ibm.com (Postfix) with ESMTP; Thu, 23 Oct 2025 15:20:50 +0000 (GMT) From: Niklas Schnelle Date: Thu, 23 Oct 2025 17:20:41 +0200 Subject: [PATCH v4 1/2] PCI: Fix isolated PCI function probing with ARI and SR-IOV Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20251023-ari_no_bus_dev-v4-1-8482e2ed10bd@linux.ibm.com> References: <20251023-ari_no_bus_dev-v4-0-8482e2ed10bd@linux.ibm.com> In-Reply-To: <20251023-ari_no_bus_dev-v4-0-8482e2ed10bd@linux.ibm.com> To: Bjorn Helgaas Cc: Jan Kiszka , Huacai Chen , linux-s390 , loongarch@lists.linux.dev, Farhan Ali , Matthew Rosato , Tianrui Zhao , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Sven Schnelle , Christian Borntraeger , Gerd Bayer , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, jailhouse-dev@googlegroups.com, Niklas Schnelle X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; 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In the case of ARI the problem is that next_ari_fn() always returns -ENODEV if dev is NULL and thus if fn 0 is missing the scan stops. For SR-IOV things are more complex. Here the problem is that the check for multifunction may fail. One example where this can occur is if the first passed-through function is a VF with devfn 8. Now in pci_scan_slot() this means it is fn 0 and thus multifunction doesn't get set. Since VFs don't get multifunction set via PCI_HEADER_TYPE_MFD it remains unset and probing stops even if there is a devfn 9. Now at the moment both of these issues are hidden on s390. The first one because ARI is detected as disabled as struct pci_bus's self is NULL even though firmware does enable and use ARI. The second issue is hidden as a side effect of commit 25f39d3dcb48 ("s390/pci: Ignore RID for isolated VFs"). This is because VFs are either put on their own virtual bus if the parent PF is not passed-through to the same instance or VFs are hotplugged once SR-IOV is enabled on the parent PF and then pci_scan_single_device() is used. Still especially the first issue prevents correct detection of ARI and the second might be a problem for other users of isolated function probing. Fix both issues by keeping things as simple as possible. If isolated function probing is enabled simply scan every possible devfn. Fixes: 189c6c33ff42 ("PCI: Extend isolated function probing to s390") Link: https://lore.kernel.org/linux-pci/d3f11e8562f589ddb2c1c83e74161bd8948= 084c3.camel@linux.ibm.com/ Signed-off-by: Niklas Schnelle --- drivers/pci/probe.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index 0ce98e18b5a876afe72af35a9f4a44d598e8d500..13495b12fbcfae4b890bbd4b2f9= 13742adf6dfed 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -2808,16 +2808,18 @@ static int next_ari_fn(struct pci_bus *bus, struct = pci_dev *dev, int fn) return next_fn; } =20 -static int next_fn(struct pci_bus *bus, struct pci_dev *dev, int fn) +static int next_fn(struct pci_bus *bus, struct pci_dev *dev, int fn, bool = isolated) { - if (pci_ari_enabled(bus)) - return next_ari_fn(bus, dev, fn); + if (!isolated) { + if (pci_ari_enabled(bus)) + return next_ari_fn(bus, dev, fn); =20 + /* only multifunction devices may have more functions */ + if (dev && !dev->multifunction) + return -ENODEV; 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Thu, 23 Oct 2025 15:20:55 GMT Received: from smtpav06.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id BF36258043; Thu, 23 Oct 2025 15:20:55 +0000 (GMT) Received: from smtpav06.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4D3B558059; Thu, 23 Oct 2025 15:20:53 +0000 (GMT) Received: from tuxmaker.boeblingen.de.ibm.com (unknown [9.152.85.9]) by smtpav06.dal12v.mail.ibm.com (Postfix) with ESMTP; Thu, 23 Oct 2025 15:20:53 +0000 (GMT) From: Niklas Schnelle Date: Thu, 23 Oct 2025 17:20:42 +0200 Subject: [PATCH v4 2/2] PCI: s390: Handle ARI on bus without associated struct pci_dev Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20251023-ari_no_bus_dev-v4-2-8482e2ed10bd@linux.ibm.com> References: <20251023-ari_no_bus_dev-v4-0-8482e2ed10bd@linux.ibm.com> In-Reply-To: <20251023-ari_no_bus_dev-v4-0-8482e2ed10bd@linux.ibm.com> To: Bjorn Helgaas Cc: Jan Kiszka , Huacai Chen , linux-s390 , loongarch@lists.linux.dev, Farhan Ali , Matthew Rosato , Tianrui Zhao , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Sven Schnelle , Christian Borntraeger , Gerd Bayer , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, jailhouse-dev@googlegroups.com, Niklas Schnelle X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; 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This associated struct pci_dev is however relied upon in pci_ari_enabled() to check whether ARI is enabled for the bus. ARI is therefor always detected as disabled. At the same time, firmware on s390 always enables and relies upon ARI thus causing a mismatch. Despite simply being a mismatch this causes problems as some PCI devices present a different SR-IOV topology depending on PCI_SRIOV_CTRL_ARI. A similar mismatch may occur with SR-IOV when virtfn_add_bus() creates new busses with no associated struct pci_dev. Here too pci_ari_enabled() on these busses returns false even if ARI is actually used. Prevent both mismatches by moving the ari_enabled flag from struct pci_dev to struct pci_bus making it independent from self in struct pci_bus. Let the bus inherit the ari_enabled state from its parent bus when there is no bridge device such that busses added by virtfn_add_bus() match their parent. For s390 set ari_enabled when the device supports ARI in the awareness that all PCIe ports on s390 systems are ARI capable. Signed-off-by: Niklas Schnelle --- arch/s390/pci/pci.c | 7 +++++++ arch/s390/pci/pci_bus.c | 10 ++++++++++ drivers/pci/pci.c | 4 ++-- drivers/pci/probe.c | 1 + include/linux/pci.h | 4 ++-- 5 files changed, 22 insertions(+), 4 deletions(-) diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c index c82c577db2bcd2143476cb8189fd89b9a4dc9836..773c0cbfc313ea1a6419a44d615= 8397dd13f6e76 100644 --- a/arch/s390/pci/pci.c +++ b/arch/s390/pci/pci.c @@ -609,6 +609,13 @@ int pcibios_device_add(struct pci_dev *pdev) continue; pci_claim_resource(pdev, i); } + /* + * The below is the s390 equivalent of pci_configure_ari() + * which we can't use directly because the bridge devices + * are hidden in firmware. + */ + if (!pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_ARI)) + zdev->zbus->bus->ari_enabled =3D 0; =20 return 0; } diff --git a/arch/s390/pci/pci_bus.c b/arch/s390/pci/pci_bus.c index 45a1c36c5a54e3a841e61cc365d3f36e9a94ba50..c887e61eb384ca98ff27d4f8af6= 9e58c715b5002 100644 --- a/arch/s390/pci/pci_bus.c +++ b/arch/s390/pci/pci_bus.c @@ -207,6 +207,16 @@ static int zpci_bus_create_pci_bus(struct zpci_bus *zb= us, struct zpci_dev *fr, s return -EFAULT; } =20 + /* + * On s390 PCI busses are virtualized and the bridge + * devices are invisible to the OS. Furthermore busses + * may exist without a devfn 0 function. Thus the normal + * ARI detection does not work. At the same time fw/hw + * has always enabled ARI when possible. Reflect the actual + * state by setting ari_enabled whenever a device on the bus + * supports it. + */ + bus->ari_enabled =3D 1; zbus->bus =3D bus; =20 return 0; diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index b14dd064006cca80ec5275e45a35d6dc2b4d0bbc..8ef3c68280a629449e0a2176d93= 8bf987c68dddf 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -3532,11 +3532,11 @@ void pci_configure_ari(struct pci_dev *dev) if (pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ARI)) { pcie_capability_set_word(bridge, PCI_EXP_DEVCTL2, PCI_EXP_DEVCTL2_ARI); - bridge->ari_enabled =3D 1; + dev->bus->ari_enabled =3D 1; } else { pcie_capability_clear_word(bridge, PCI_EXP_DEVCTL2, PCI_EXP_DEVCTL2_ARI); - bridge->ari_enabled =3D 0; + dev->bus->ari_enabled =3D 0; } } =20 diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index 13495b12fbcfae4b890bbd4b2f913742adf6dfed..338bb7e6738d27865e3d50aa309= 4ca5ab29a6a47 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -1216,6 +1216,7 @@ static struct pci_bus *pci_alloc_child_bus(struct pci= _bus *parent, =20 if (!bridge) { child->dev.parent =3D parent->bridge; + child->ari_enabled =3D parent->ari_enabled; goto add_dev; } =20 diff --git a/include/linux/pci.h b/include/linux/pci.h index d1fdf81fbe1e427aecbc951fa3fdf65c20450b05..a9c3dbf17339e523362bd179ad3= c7c8c91293cf0 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -445,7 +445,6 @@ struct pci_dev { unsigned int irq_reroute_variant:2; /* Needs IRQ rerouting variant */ unsigned int msi_enabled:1; unsigned int msix_enabled:1; - unsigned int ari_enabled:1; /* ARI forwarding */ unsigned int ats_enabled:1; /* Address Translation Svc */ unsigned int pasid_enabled:1; /* Process Address Space ID */ unsigned int pri_enabled:1; /* Page Request Interface */ @@ -691,6 +690,7 @@ struct pci_bus { unsigned int is_added:1; unsigned int unsafe_warn:1; /* warned about RW1C config write */ unsigned int flit_mode:1; /* Link in Flit mode */ + unsigned int ari_enabled:1; /* ARI forwarding enabled */ }; =20 #define to_pci_bus(n) container_of(n, struct pci_bus, dev) @@ -2740,7 +2740,7 @@ static inline bool pci_is_dev_assigned(struct pci_dev= *pdev) */ static inline bool pci_ari_enabled(struct pci_bus *bus) { - return bus->self && bus->self->ari_enabled; + return bus->ari_enabled; } =20 /** --=20 2.48.1