From 7b3b1e5a87b2f5e35c52b5386d7c327be869454f Mon Sep 17 00:00:00 2001 From: Long Li Date: Mon, 16 Mar 2026 14:07:42 -0700 Subject: PCI: hv: Set default NUMA node to 0 for devices without affinity info When hv_pci_assign_numa_node() processes a device that does not have HV_PCI_DEVICE_FLAG_NUMA_AFFINITY set or has an out-of-range virtual_numa_node, the device NUMA node is left unset. On x86_64, the uninitialized default happens to be 0, but on ARM64 it is NUMA_NO_NODE (-1). Tests show that when no NUMA information is available from the Hyper-V host, devices perform best when assigned to node 0. With NUMA_NO_NODE the kernel may spread work across NUMA nodes, which degrades performance on Hyper-V, particularly for high-throughput devices like MANA. Always set the device NUMA node to 0 before the conditional NUMA affinity check, so that devices get a performant default when the host provides no NUMA information, and behavior is consistent on both x86_64 and ARM64. Fixes: 999dd956d838 ("PCI: hv: Add support for protocol 1.3 and support PCI_BUS_RELATIONS2") Signed-off-by: Long Li Reviewed-by: Michael Kelley Signed-off-by: Wei Liu --- drivers/pci/controller/pci-hyperv.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c index 2c7a406b4ba8..38a790f642a1 100644 --- a/drivers/pci/controller/pci-hyperv.c +++ b/drivers/pci/controller/pci-hyperv.c @@ -2485,6 +2485,14 @@ static void hv_pci_assign_numa_node(struct hv_pcibus_device *hbus) if (!hv_dev) continue; + /* + * If the Hyper-V host doesn't provide a NUMA node for the + * device, default to node 0. With NUMA_NO_NODE the kernel + * may spread work across NUMA nodes, which degrades + * performance on Hyper-V. + */ + set_dev_node(&dev->dev, 0); + if (hv_dev->desc.flags & HV_PCI_DEVICE_FLAG_NUMA_AFFINITY && hv_dev->desc.virtual_numa_node < num_possible_nodes()) /* -- cgit v1.2.3