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Fri, 13 Mar 2026 16:49:47 +0000 (GMT) From: Gerd Bayer Date: Fri, 13 Mar 2026 17:49:34 +0100 Subject: [PATCH v4 1/2] PCI: AtomicOps: Do not enable if root-port capabilities are unknown 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: <20260313-fix_pciatops-v4-1-93bc70a63935@linux.ibm.com> References: <20260313-fix_pciatops-v4-0-93bc70a63935@linux.ibm.com> In-Reply-To: <20260313-fix_pciatops-v4-0-93bc70a63935@linux.ibm.com> To: Bjorn Helgaas , Jay Cornwall , Felix Kuehling Cc: Leon Romanovsky , Niklas Schnelle , Alexander Schmidt , linux-s390@vger.kernel.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-rdma@vger.kernel.org, Gerd Bayer , stable@vger.kernel.org X-Mailer: b4 0.14.2 X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=QKtlhwLL c=1 sm=1 tr=0 ts=69b44031 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=IkcTkHD0fZMA:10 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VnNF1IyMAAAA:8 a=VwQbUJbxAAAA:8 a=y92EubQfrlY9IES1mRIA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzEzMDEzMiBTYWx0ZWRfX4ncpxEQH1Um2 SeKbwV/YN36qzbenLvd+gqxicZGwNgUxdEoIjnFI3hLyx1tDUA/yBVWUTeSzqYfy075SZZAdigf D7E86Uwyb1Y0/h/oHWD7bbTDD70jb5Pm2yzEO+bo9hHL/UaE8BUqJZzNy/X4/ZgqFAJTBOHZL5x KsrHur+RwJZy49oIEUjUrWKWf8gWLWynMiRUYW9ZYCwECGiUDgIY7SC6txkjg91X1vhVrZ1iQ8P eulzOCdOqE3t4YRH/BDWfEGwcjTXVg8ZtX40g0XbioRZ05vS2b3CXS8+7Lxpo8KALSkqpYuHj4t uEws1O5Glm4OS5xzvITnfgBbEU3jPUefcL5OuRp4lCKz5YRuVBtfM7JAxVR0dn5GSXlT0zVBVnP odiiOvwTNLHUWnjXfCeSCLaK0/SlpnfC1KyB5vuDoY7SeYBtbWTMLalf5dPwvaUChQZjCdWMZR6 sok0cXpVO4nyaSnlPZA== X-Proofpoint-ORIG-GUID: w9G9ymIRkTgXHzujdcdXrv3z3bzCTVaI X-Proofpoint-GUID: ZVhVvyM9W43RBLhyrSNrpmqRkpnEdcuC 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=2026-03-13_03,2026-03-13_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 suspectscore=0 impostorscore=0 clxscore=1015 priorityscore=1501 bulkscore=0 adultscore=0 phishscore=0 spamscore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603130132 When inspecting the config space of a Connect-X physical function in an s390 system after it was initialized by the mlx5_core device driver, we found the function to be enabled to request AtomicOps despite the system's root-complex lacking support for completing them: 1ed0:00:00.1 Ethernet controller: Mellanox Technologies MT2894 Family [Conn= ectX-6 Lx] Subsystem: Mellanox Technologies Device 0002 [...] DevCtl2: Completion Timeout: 50us to 50ms, TimeoutDis- AtomicOpsCtl: ReqEn+ IDOReq- IDOCompl- LTR- EmergencyPowerReductionReq- 10BitTagReq- OBFF Disabled, EETLPPrefixBlk- Turns out the device driver calls pci_enable_atomic_ops_to_root() which defaulted to enable AtomicOps requests even if it had no information about the root-port that the PCIe device is attached to. Change to logic of pci_enable_atomic_ops_to_root() to fully traverse the PCIe tree upwards, check that the bridge devices support delivering AtomicOps transactions, and finally check that there is a root-port at the end that does support completing AtomicOps. Do not enable AtomicOps requests if nothing can be learned about how the device is attached - e.g. if it is on an "isolated" bus, as in s390. Reported-by: Alexander Schmidt Cc: stable@vger.kernel.org Fixes: 430a23689dea ("PCI: Add pci_enable_atomic_ops_to_root()") Signed-off-by: Gerd Bayer --- drivers/pci/pci.c | 30 ++++++++++++++---------------- 1 file changed, 14 insertions(+), 16 deletions(-) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 8479c2e1f74f1044416281aba11bf071ea89488a..94e90988df86b3278b1b6abbc32= 6abf9b4a4a962 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -3676,7 +3676,7 @@ void pci_acs_init(struct pci_dev *dev) int pci_enable_atomic_ops_to_root(struct pci_dev *dev, u32 cap_mask) { struct pci_bus *bus =3D dev->bus; - struct pci_dev *bridge; + struct pci_dev *bridge =3D NULL; u32 cap, ctl2; =20 /* @@ -3714,29 +3714,27 @@ int pci_enable_atomic_ops_to_root(struct pci_dev *d= ev, u32 cap_mask) switch (pci_pcie_type(bridge)) { /* Ensure switch ports support AtomicOp routing */ case PCI_EXP_TYPE_UPSTREAM: - case PCI_EXP_TYPE_DOWNSTREAM: - if (!(cap & PCI_EXP_DEVCAP2_ATOMIC_ROUTE)) - return -EINVAL; - break; - - /* Ensure root port supports all the sizes we care about */ - case PCI_EXP_TYPE_ROOT_PORT: - if ((cap & cap_mask) !=3D cap_mask) - return -EINVAL; - break; - } - - /* Ensure upstream ports don't block AtomicOps on egress */ - if (pci_pcie_type(bridge) =3D=3D PCI_EXP_TYPE_UPSTREAM) { + /* Upstream ports must not block AtomicOps on egress */ pcie_capability_read_dword(bridge, PCI_EXP_DEVCTL2, &ctl2); if (ctl2 & PCI_EXP_DEVCTL2_ATOMIC_EGRESS_BLOCK) return -EINVAL; + fallthrough; + /* All switch ports need to route AtomicOps */ + case PCI_EXP_TYPE_DOWNSTREAM: + if (!(cap & PCI_EXP_DEVCAP2_ATOMIC_ROUTE)) + return -EINVAL; + break; } - bus =3D bus->parent; } =20 + /* Finally, last bridge must be root port and support requested sizes */ + if ((!bridge) || + (pci_pcie_type(bridge) !=3D PCI_EXP_TYPE_ROOT_PORT) || + ((cap & cap_mask) !=3D cap_mask)) + return -EINVAL; + pcie_capability_set_word(dev, PCI_EXP_DEVCTL2, PCI_EXP_DEVCTL2_ATOMIC_REQ); return 0; --=20 2.51.0