Public bug reported: Team,
This bug is created to understand Ubuntu Kernel team on pull & merge plans in resolute ? Patch: https://patchwork.ozlabs.org/project/linux-pci/patch/[email protected]/ We see this already up streamed to v7.3 version *** commit details** which explains the issue it is getting addressed commit 40cce45b921f7930886bcba43069edc579725457 Author: Nikola Prica <[email protected]> Date: Mon Sep 21 13:19:03 2026 +0200 PCI: Accept AtomicOps already enabled by the hypervisor pci_enable_atomic_ops_to_root() currently fails when no Root Port is visible. That is common in passthrough guests (ESXi, Hyper-V): the Endpoint is assigned to the VM, but the Root Port above it is not visible in the guest topology. In those setups the hypervisor may already have enabled AtomicOp Requester Enable on the device. If PCI_EXP_DEVCTL2_ATOMIC_REQ is set, treat AtomicOps as already enabled and return success instead of failing the Root Port walk. After 1ae8c4ce1570 ("PCI: Enable AtomicOps only if Root Port supports them"), pci_enable_atomic_ops_to_root() always returns failure if the Root Port is not visible, so drivers don't use atomics when they could. On systems where the Root Port is not visible but *does* support AtomicOps, this is a regression: prior to 1ae8c4ce1570, it enabled AtomicOps in the endpoint and returned success. Fixes: 1ae8c4ce1570 ("PCI: Enable AtomicOps only if Root Port supports them") Signed-off-by: Nikola Prica <[email protected]> [bhelgaas: commit log, code comment] Signed-off-by: Bjorn Helgaas <[email protected]> Tested-by: Gerd Bayer <[email protected]> Reviewed-by: Christian König <[email protected]> Reviewed-by: Gerd Bayer <[email protected]> Link: https://patch.msgid.link/[email protected] diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index b2879a6be5f8..8cc6a89130b5 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -3769,8 +3769,21 @@ int pci_enable_atomic_ops_to_root(struct pci_dev *dev, u32 cap_mask) } root = pcie_find_root_port(dev); - if (!root) + if (!root) { + + /* + * A hypervisor may expose a topology with the root port + * not visible to the guest. If the hypervisor has already + * set AtomicOp Requester Enable in the endpoint, we assume + * it has verified support in the root port, so it is safe + * for the driver to use AtomicOps. + */ + pcie_capability_read_dword(dev, PCI_EXP_DEVCTL2, &ctl2); + if (ctl2 & PCI_EXP_DEVCTL2_ATOMIC_REQ) + return 0; + return -EINVAL; + } pcie_capability_read_dword(root, PCI_EXP_DEVCAP2, &cap); if ((cap & cap_mask) != cap_mask) ~ ~ ** ** Affects: linux (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2172445 Title: Query and Ubuntu merge plans for PCI: Accept AtomicOps already enabled by the hypervisor To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2172445/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
