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Wed, 25 Mar 2026 15:16:24 +0000 (GMT) From: Gerd Bayer Date: Wed, 25 Mar 2026 16:16:17 +0100 Subject: [PATCH v6 1/2] PCI: AtomicOps: Do not enable without support in root complex Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260325-fix_pciatops-v6-1-10bf19d76dd1@linux.ibm.com> References: <20260325-fix_pciatops-v6-0-10bf19d76dd1@linux.ibm.com> In-Reply-To: <20260325-fix_pciatops-v6-0-10bf19d76dd1@linux.ibm.com> To: Bjorn Helgaas , Jay Cornwall , Felix Kuehling , Christian Borntraeger , Niklas Schnelle Cc: Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Sven Schnelle , Leon Romanovsky , 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-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzI1MDEwNiBTYWx0ZWRfX98LmQ4B2W+DB Gv/WPBiDPwdfzl5bzCk5adAkUwh5VV5BbdhQK5B49PQUc8nBfhRp+9PD7fJSq+FB6A/fFJNkrOe uVZGeg3NQuxThg+5hZA1mhIyiQkbFkk5UeaWt5ED15h1VoHLOtF5Z3dkOnzr2Zt/m2K5lYT6lTj 3FCCMi/v848dty+N1CO7XwQjSi28Yj1HlOeH33zJr0uYsXY5TbgJGgfPSCqtoBu7Xz/NgItOPy7 YPF22kN0rFKOJ1MrN6URjahJI81N/1XICJYlxVzO6SL3Cf1BYyi66VxY2evlz9Ae06kljBtofzs xjFi7hp+OhGsj+H8botRH1CVB2joV27ohhdVJiZGMi5cbaUOwmPF8J5CfIXWqs/EO0n/4YIyBHi wUSWw6QEVSfHB9XEw6QlwbvGF2sNHzVHE8BMXo22KEcs5iRa+9PgrSXB/pqRh3DEV/Q1RJh5eZO jWoICEj1n1m85QagFZw== X-Authority-Analysis: v=2.4 cv=JK42csKb c=1 sm=1 tr=0 ts=69c3fc4d cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=VnNF1IyMAAAA:8 a=VwQbUJbxAAAA:8 a=Hx5SdpTRtzwH465PzOMA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-ORIG-GUID: rnuTNvRXxuHVYp6kF1wGfPuuu60UW4sL X-Proofpoint-GUID: xhuNwk8t0ZsChDnOiSezc9PsQ1zgGuCj 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=2026-03-25_04,2026-03-24_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 clxscore=1015 priorityscore=1501 malwarescore=0 adultscore=0 spamscore=0 suspectscore=0 phishscore=0 lowpriorityscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603250106 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 [ConnectX-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. Similarly, AtomicOps requests are enabled for root complex integrated endpoints (RCiEPs) unconditionally. Change the 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 - or that the support for completing AtomicOps at the root complex is announced through some other arch specific way. Introduce a new pcibios_connects_to_atomicops_capable_rc() function to implement the check - and default to always "true". This leaves the semantics for today's RCiEPs intact. Pass in the device in question and the requested capabilities for future expansions. For s390, override pcibios_connects_to_atomicops_capable_rc() to always return "false". Do not change the enablement of AtomicOps requests if there is no positive confirmation that the root complex can complete PCIe AtomicOps. Reported-by: Alexander Schmidt Cc: stable@vger.kernel.org Fixes: 430a23689dea ("PCI: Add pci_enable_atomic_ops_to_root()") Signed-off-by: Gerd Bayer --- arch/s390/pci/pci.c | 5 +++++ drivers/pci/pci.c | 48 +++++++++++++++++++++++++++++++----------------- include/linux/pci.h | 1 + 3 files changed, 37 insertions(+), 17 deletions(-) diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c index 2a430722cbe415dd56c92fed2e513e524f46481a..a0bef77082a153a258fbe4abb1070b22e020888e 100644 --- a/arch/s390/pci/pci.c +++ b/arch/s390/pci/pci.c @@ -265,6 +265,11 @@ static int zpci_cfg_store(struct zpci_dev *zdev, int offset, u32 val, u8 len) return rc; } +bool pcibios_connects_to_atomicops_capable_rc(struct pci_dev *dev, u32 cap_mask) +{ + return false; +} + resource_size_t pcibios_align_resource(void *data, const struct resource *res, resource_size_t size, resource_size_t align) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 8479c2e1f74f1044416281aba11bf071ea89488a..006aa589926cb290de43f152100ddaf9961407d1 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -3660,6 +3660,19 @@ void pci_acs_init(struct pci_dev *dev) pci_disable_broken_acs_cap(dev); } +static bool pci_is_atomicops_capable_rp(struct pci_dev *dev, u32 cap, u32 cap_mask) +{ + if (!dev || !(pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT)) + return false; + + return (cap & cap_mask) == cap_mask; +} + +bool __weak pcibios_connects_to_atomicops_capable_rc(struct pci_dev *dev, u32 cap_mask) +{ + return true; +} + /** * pci_enable_atomic_ops_to_root - enable AtomicOp requests to root port * @dev: the PCI device @@ -3676,8 +3689,9 @@ 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 = dev->bus; - struct pci_dev *bridge; - u32 cap, ctl2; + struct pci_dev *bridge = NULL; + u32 cap = 0; + u32 ctl2; /* * Per PCIe r5.0, sec 9.3.5.10, the AtomicOp Requester Enable bit @@ -3714,29 +3728,29 @@ int pci_enable_atomic_ops_to_root(struct pci_dev *dev, 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) != cap_mask) - return -EINVAL; - break; - } - - /* Ensure upstream ports don't block AtomicOps on egress */ - if (pci_pcie_type(bridge) == 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 = bus->parent; } + /* + * Finally, last bridge must be root port and support requested sizes + * or firmware asserts support + */ + if (!(pci_is_atomicops_capable_rp(bridge, cap, cap_mask) || + pcibios_connects_to_atomicops_capable_rc(dev, cap_mask))) + return -EINVAL; + pcie_capability_set_word(dev, PCI_EXP_DEVCTL2, PCI_EXP_DEVCTL2_ATOMIC_REQ); return 0; diff --git a/include/linux/pci.h b/include/linux/pci.h index 1c270f1d512301de4d462fe7e5097c32af5c6f8d..ef90604c39859ea8e61e5392d0bdaa1b0e43874b 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -692,6 +692,7 @@ void pci_set_host_bridge_release(struct pci_host_bridge *bridge, void *release_data); int pcibios_root_bridge_prepare(struct pci_host_bridge *bridge); +bool pcibios_connects_to_atomicops_capable_rc(struct pci_dev *dev, u32 cap_mask); #define PCI_REGION_FLAG_MASK 0x0fU /* These bits of resource flags tell us the PCI region flags */ -- 2.51.0