Re: [PATCH 2/2] hw/arm/virt: Don't create device-tree node for empty NUMA node

[Andrew Jones]

On Wed, Oct 06, 2021 at 06:22:09PM +0800, Gavin Shan wrote:
> The empty NUMA node, where no memory resides, are allowed. For
> example, the following command line specifies two empty NUMA nodes.
> With this, QEMU fails to boot because of the conflicting device-tree
> node names, as the following error message indicates.
> 
>   /home/gavin/sandbox/qemu.main/build/qemu-system-aarch64 \
>   -accel kvm -machine virt,gic-version=host               \
>   -cpu host -smp 4,sockets=2,cores=2,threads=1            \
>   -m 1024M,slots=16,maxmem=64G                            \
>   -object memory-backend-ram,id=mem0,size=512M            \
>   -object memory-backend-ram,id=mem1,size=512M            \
>   -numa node,nodeid=0,cpus=0-1,memdev=mem0                \
>   -numa node,nodeid=1,cpus=2-3,memdev=mem1                \
>   -numa node,nodeid=2                                     \
>   -numa node,nodeid=3
>     :
>   qemu-system-aarch64: FDT: Failed to create subnode /memory@80000000: 
> FDT_ERR_EXISTS
> 
> As specified by linux device-tree binding document, the device-tree
> nodes for these empty NUMA nodes shouldn't be generated. However,
> the corresponding NUMA node IDs should be included in the distance
> map device-tree node. This skips populating the device-tree nodes
> for these empty NUMA nodes to avoid the error, so that QEMU can be
> started successfully.
> 
> Signed-off-by: Gavin Shan <gshan@redhat.com>
> ---
>  hw/arm/boot.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/hw/arm/boot.c b/hw/arm/boot.c
> index 57efb61ee4..4e5898fcdc 100644
> --- a/hw/arm/boot.c
> +++ b/hw/arm/boot.c
> @@ -603,6 +603,10 @@ int arm_load_dtb(hwaddr addr, const struct arm_boot_info 
> *binfo,
>          mem_base = binfo->loader_start;
>          for (i = 0; i < ms->numa_state->num_nodes; i++) {
>              mem_len = ms->numa_state->nodes[i].node_mem;
> +            if (!mem_len) {
> +                continue;
> +            }
> +
>              rc = fdt_add_memory_node(fdt, acells, mem_base,
>                                       scells, mem_len, i);
>              if (rc < 0) {
> -- 
> 2.23.0
>

Reviewed-by: Andrew Jones <drjones@redhat.com>