Re: [PATCH v5] hw/arm/virt: Don't create device-tree node for empty NUMA node

[Richard Henderson <richard.henderson@linaro.org>]

On 10/15/21 5:42 AM, 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. The memory hotplug through device-tree on ARM64 isn't existing
> so far and it's not necessary to require the user to provide a distance
> map. Furthermore, the default distance map Linux generates may even be
> sufficient. So this simply 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>
> ---
> v5: Improved commit log and comments as Drew suggested.

Queued to target-arm, thanks.


r~