Re: [PATCH v3 1/3] numa: Validate cluster and NUMA node boundary if required

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 25/2/23 07:35, Gavin Shan wrote:
> For some architectures like ARM64, multiple CPUs in one cluster can be
> associated with different NUMA nodes, which is irregular configuration
> because we shouldn't have this in baremetal environment. The irregular
> configuration causes Linux guest to misbehave, as the following warning
> messages indicate.
> 
>    -smp 6,maxcpus=6,sockets=2,clusters=1,cores=3,threads=1 \
>    -numa node,nodeid=0,cpus=0-1,memdev=ram0                \
>    -numa node,nodeid=1,cpus=2-3,memdev=ram1                \
>    -numa node,nodeid=2,cpus=4-5,memdev=ram2                \
> 
>    ------------[ cut here ]------------
>    WARNING: CPU: 0 PID: 1 at kernel/sched/topology.c:2271 build_sched_domains+0x284/0x910
>    Modules linked in:
>    CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.14.0-268.el9.aarch64 #1
>    pstate: 00400005 (nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>    pc : build_sched_domains+0x284/0x910
>    lr : build_sched_domains+0x184/0x910
>    sp : ffff80000804bd50
>    x29: ffff80000804bd50 x28: 0000000000000002 x27: 0000000000000000
>    x26: ffff800009cf9a80 x25: 0000000000000000 x24: ffff800009cbf840
>    x23: ffff000080325000 x22: ffff0000005df800 x21: ffff80000a4ce508
>    x20: 0000000000000000 x19: ffff000080324440 x18: 0000000000000014
>    x17: 00000000388925c0 x16: 000000005386a066 x15: 000000009c10cc2e
>    x14: 00000000000001c0 x13: 0000000000000001 x12: ffff00007fffb1a0
>    x11: ffff00007fffb180 x10: ffff80000a4ce508 x9 : 0000000000000041
>    x8 : ffff80000a4ce500 x7 : ffff80000a4cf920 x6 : 0000000000000001
>    x5 : 0000000000000001 x4 : 0000000000000007 x3 : 0000000000000002
>    x2 : 0000000000001000 x1 : ffff80000a4cf928 x0 : 0000000000000001
>    Call trace:
>     build_sched_domains+0x284/0x910
>     sched_init_domains+0xac/0xe0
>     sched_init_smp+0x48/0xc8
>     kernel_init_freeable+0x140/0x1ac
>     kernel_init+0x28/0x140
>     ret_from_fork+0x10/0x20
> 
> Improve the situation to warn when multiple CPUs in one cluster have
> been associated with different NUMA nodes. However, one NUMA node is
> allowed to be associated with different clusters.
> 
> Signed-off-by: Gavin Shan <gshan@redhat.com>
> ---
>   hw/core/machine.c   | 42 ++++++++++++++++++++++++++++++++++++++++++
>   include/hw/boards.h |  1 +
>   2 files changed, 43 insertions(+)
> 
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index f29e700ee4..3513df5a86 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -1252,6 +1252,45 @@ static void machine_numa_finish_cpu_init(MachineState *machine)
>       g_string_free(s, true);
>   }
>   
> +static void validate_cpu_cluster_to_numa_boundary(MachineState *ms)
> +{
> +    MachineClass *mc = MACHINE_GET_CLASS(ms);
> +    NumaState *state = ms->numa_state;
> +    const CPUArchIdList *possible_cpus = mc->possible_cpu_arch_ids(ms);
> +    const CPUArchId *cpus = possible_cpus->cpus;
> +    int len = possible_cpus->len, i, j;

(Nitpicking, 'len' variable is not very useful).

> +
> +    if (state->num_nodes <= 1 || len <= 1) {
> +        return;
> +    }
> +
> +    /*
> +     * The Linux scheduling domain can't be parsed when the multiple CPUs
> +     * in one cluster have been associated with different NUMA nodes. However,
> +     * it's fine to associate one NUMA node with CPUs in different clusters.
> +     */
> +    for (i = 0; i < len; i++) {
> +        for (j = i + 1; j < len; j++) {
> +            if (cpus[i].props.has_socket_id &&
> +                cpus[i].props.has_cluster_id &&
> +                cpus[i].props.has_node_id &&
> +                cpus[j].props.has_socket_id &&
> +                cpus[j].props.has_cluster_id &&
> +                cpus[j].props.has_node_id &&
> +                cpus[i].props.socket_id == cpus[j].props.socket_id &&
> +                cpus[i].props.cluster_id == cpus[j].props.cluster_id &&
> +                cpus[i].props.node_id != cpus[j].props.node_id) {
> +                warn_report("CPU-%d and CPU-%d in socket-%ld-cluster-%ld "
> +                             "have been associated with node-%ld and node-%ld "
> +                             "respectively. It can cause OSes like Linux to"
> +                             "misbehave", i, j, cpus[i].props.socket_id,
> +                             cpus[i].props.cluster_id, cpus[i].props.node_id,
> +                             cpus[j].props.node_id);

machine_run_board_init() takes an Error* argument, but is only called
once by qemu_init_board() with errp=&error_fatal. I suppose using
warn_report() here is OK.

Acked-by: Philippe Mathieu-Daudé <philmd@linaro.org>

> +            }
> +        }
> +    }
> +}
> +
>   MemoryRegion *machine_consume_memdev(MachineState *machine,
>                                        HostMemoryBackend *backend)
>   {
> @@ -1337,6 +1376,9 @@ void machine_run_board_init(MachineState *machine, const char *mem_path, Error *
>           numa_complete_configuration(machine);
>           if (machine->numa_state->num_nodes) {
>               machine_numa_finish_cpu_init(machine);
> +            if (machine_class->cpu_cluster_has_numa_boundary) {
> +                validate_cpu_cluster_to_numa_boundary(machine);
> +            }
>           }
>       }