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

[Michael Kelley (LINUX)]

From: longli@xxxxxxxxxxxxxxxxx <longli@xxxxxxxxxxxxxxxxx> Sent: Wednesday, January 19, 2022 11:59 AM
> 
> 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>
> 
> 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()
> ---
>  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

Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>