linux-kernel - [Patch v3] PCI: hv: Fix NUMA node assignment when kernel boots with custom NUMA topology

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Date:   Wed, 19 Jan 2022 11:59:06 -0800
From:   longli@...uxonhyperv.com
To:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hyperv@...r.kernel.org, paekkaladevi@...rosoft.com
Cc:     Long Li <longli@...rosoft.com>
Subject: [Patch v3] PCI: hv: Fix NUMA node assignment when kernel boots with custom NUMA topology

From: Long Li <longli@...rosoft.com>

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@...rosoft.com>

Change log:
v2: use numa_map_to_online_node() to assign a node to device (suggested by
Michael Kelly <mikelley@...rosoft.com>)

v3: add "Fixes" and check for num_possible_nodes()
---
 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 6c9efeefae1b..b5276e81bb44 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -2129,8 +2129,17 @@ 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