linux-kernel - [Patch v2] PCI: hv: Fix NUMA node assignment when kernel boots with custom NUMA topology

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Message-Id: <1642560329-5012-1-git-send-email-longli@linuxonhyperv.com>
Date:   Tue, 18 Jan 2022 18:45:29 -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 v2] 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".

Signed-off-by: Long Li <longli@...rosoft.com>

Change from v1:
Use numa_map_to_online_node() to assign a node to device (suggested by
Michael Kelly <mikelley@...rosoft.com>)

---
 drivers/pci/controller/pci-hyperv.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index 6c9efeefae1b..c7519add6f13 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -2130,7 +2130,15 @@ static void hv_pci_assign_numa_node(struct hv_pcibus_device *hbus)
 			continue;
 
 		if (hv_dev->desc.flags & HV_PCI_DEVICE_FLAG_NUMA_AFFINITY)
-			set_dev_node(&dev->dev, hv_dev->desc.virtual_numa_node);
+			/*
+			 * 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