Re: [PATCH 1/2] hmat acpi: Do not add Memory Proximity Domain Attributes Structure targetting non existent memory.

[Gregory Price <gregory.price@memverge.com>]

On Thu, Feb 29, 2024 at 04:25:44PM +0000, Jonathan Cameron wrote:
> If qemu is started with a proximity node containing CPUs alone,
> it will provide one of these structures to say memory in this
> node is directly connected to itself.
> 
> This description is arguably pointless even if there is memory
> in the node.  If there is no memory present, and hence no SRAT
> entry it breaks Linux HMAT passing and the table is rejected.
> 
> https://elixir.bootlin.com/linux/latest/source/drivers/acpi/numa/hmat.c#L444
> 

Nit: This link becomes out of date pretty much immediately, consider
using a versioned link.

> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> ---
>  hw/acpi/hmat.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/hw/acpi/hmat.c b/hw/acpi/hmat.c
> index 3042d223c8..723ae28d32 100644
> --- a/hw/acpi/hmat.c
> +++ b/hw/acpi/hmat.c
> @@ -204,6 +204,13 @@ static void hmat_build_table_structs(GArray *table_data, NumaState *numa_state)
>      build_append_int_noprefix(table_data, 0, 4); /* Reserved */
>  
>      for (i = 0; i < numa_state->num_nodes; i++) {
> +        /*
> +         * Linux rejects whole HMAT table if a node with no memory
> +         * has one of these structures listing it as a target.
> +         */
> +        if (!numa_state->nodes[i].node_mem) {
> +            continue;
> +        }
>          flags = 0;
>  
>          if (numa_state->nodes[i].initiator < MAX_NODES) {
> -- 
> 2.39.2
> 
>