RE: [EXTERNAL] [Patch v4] PCI: hv: Fix NUMA node assignment when kernel boots with custom NUMA topology

[Purna Pavan Chandra Aekkaladevi]

-----Original Message-----
From: longli@xxxxxxxxxxxxxxxxx <longli@xxxxxxxxxxxxxxxxx> 
Sent: Thursday, January 27, 2022 7:14 AM
To: linux-pci@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-hyperv@xxxxxxxxxxxxxxx; Purna Pavan Chandra Aekkaladevi <paekkaladevi@xxxxxxxxxxxxx>
Cc: Long Li <longli@xxxxxxxxxxxxx>
Subject: [EXTERNAL] [Patch v4] PCI: hv: Fix NUMA node assignment when kernel boots with custom NUMA topology

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From: Long Li <longli@xxxxxxxxxxxxx>

When kernel boots with a NUMA topology with some NUMA nodes offline, the PCI driver should only set an online NUMA node on the device. This can happen during KDUMP where some NUMA nodes are not made online by the KDUMP kernel.

This patch also fixes the case where kernel is booting with "numa=off".

Fixes: 999dd956d838 ("PCI: hv: Add support for protocol 1.3 and support PCI_BUS_RELATIONS2")
Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>
Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
Tested-by: Purna Pavan Chandra Aekkaladevi <paekkaladevi@xxxxxxxxxxxxx>
---
Change log:
v2: use numa_map_to_online_node() to assign a node to device (suggested by Michael Kelly <mikelley@xxxxxxxxxxxxx>)
v3: add "Fixes" and check for num_possible_nodes()
v4: fix commit message format

 drivers/pci/controller/pci-hyperv.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index 20ea2ee330b8..ae0bc2fee4ca 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -2155,8 +2155,17 @@ static void hv_pci_assign_numa_node(struct hv_pcibus_device *hbus)
                if (!hv_dev)
                        continue;

-               if (hv_dev->desc.flags & HV_PCI_DEVICE_FLAG_NUMA_AFFINITY)
-                       set_dev_node(&dev->dev, hv_dev->desc.virtual_numa_node);
+               if (hv_dev->desc.flags & HV_PCI_DEVICE_FLAG_NUMA_AFFINITY &&
+                   hv_dev->desc.virtual_numa_node < num_possible_nodes())
+                       /*
+                        * The kernel may boot with some NUMA nodes offline
+                        * (e.g. in a KDUMP kernel) or with NUMA disabled via
+                        * "numa=off". In those cases, adjust the host provided
+                        * NUMA node to a valid NUMA node used by the kernel.
+                        */
+                       set_dev_node(&dev->dev,
+                                    numa_map_to_online_node(
+                                            
+ hv_dev->desc.virtual_numa_node));

                put_pcichild(hv_dev);
        }
--
2.25.1