Re: [PATCH] PCI: Remove warning about host bridge on unknown NUMA node

[Yunsheng Lin]

On 2026/3/5 8:21, Bjorn Helgaas wrote:
> ad5086108b9f ("PCI: Warn if no host bridge NUMA node info") added warnings
> like this when there are multiple NUMA nodes and we discover a PCI host
> bridge where no node is specified, e.g., there's no ACPI _PXM method or DT
> "numa-node-id" property:
> 
>   pci_bus 0000:ff: Unknown NUMA node; performance will be reduced
> 
> The hope was that the message would encourage vendors to add NUMA node
> information to their firmware or DTs, but that hasn't happened.  The
> message just leads to bug reports that we can't do anything about.
> 
> In some cases BIOS has _PXM methods for some bridges but not others, which
> suggests that the vendor thinks node information isn't useful to the OS,
> e.g., maybe there are no real devices below the bridge.
> 
> Remove the warning message when the NUMA node is unknown.  If it is known,
> include it in an existing message:
> 
>   PCI host bridge to bus 0000:00 NUMA node 0

LGTM.
Reviewed-by: Yunsheng Lin <linyunsheng@xxxxxxxxxx>

> 
> Reported-by: Paul Menzel <pmenzel@xxxxxxxxxxxxx>
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218951
> Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> ---
>  drivers/pci/probe.c | 18 +++++++++++-------
>  1 file changed, 11 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index bccc7a4bdd79..e3e81926a6f3 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -993,9 +993,9 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
>  	LIST_HEAD(resources);
>  	struct resource *res, *next_res;
>  	bool bus_registered = false;
> -	char addr[64], *fmt;
> +	char numa[32], addr[64], *fmt;
>  	const char *name;
> -	int err;
> +	int err, node;
>  
>  	bus = pci_alloc_bus(NULL);
>  	if (!bus)
> @@ -1071,13 +1071,17 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
>  	/* Create legacy_io and legacy_mem files for this bus */
>  	pci_create_legacy_files(bus);
>  
> +	numa[0] = '\0';
> +	if (nr_node_ids > 1) {
> +		node = pcibus_to_node(bus);
> +		if (node != NUMA_NO_NODE)
> +			snprintf(numa, sizeof(numa), " on NUMA node %u", node);
> +	}
> +
>  	if (parent)
> -		dev_info(parent, "PCI host bridge to bus %s\n", name);
> +		dev_info(parent, "PCI host bridge to bus %s%s\n", name, numa);
>  	else
> -		pr_info("PCI host bridge to bus %s\n", name);
> -
> -	if (nr_node_ids > 1 && pcibus_to_node(bus) == NUMA_NO_NODE)
> -		dev_warn(&bus->dev, "Unknown NUMA node; performance will be reduced\n");
> +		pr_info("PCI host bridge to bus %s%s\n", name, numa);
>  
>  	/* Check if the boot configuration by FW needs to be preserved */
>  	bridge->preserve_config = pci_preserve_config(bridge);