Re: [PATCH v2 0/4] NUMA: Apply socket-NUMA-node boundary for aarch64 and RiscV machines

[Daniel Henrique Barboza]

On 2/23/23 05:13, Gavin Shan wrote:
> For arm64 and RiscV architecture, the driver (/base/arch_topology.c) is
> used to populate the CPU topology in the Linux guest. It's required that
> the CPUs in one socket can't span mutiple NUMA nodes. Otherwise, the Linux
> scheduling domain can't be sorted out, as the following warning message
> indicates. To avoid the unexpected confusion, this series attempts to
> rejects such kind of insane configurations.
>
>     -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                \


And why is this a QEMU problem? This doesn't hurt ACPI.

Also, this restriction impacts breaks ARM guests in the wild that are running
non-Linux OSes. I don't see why we should impact use cases that has nothing to
do with Linux Kernel feelings about sockets - NUMA nodes exclusivity.


Thanks,


Daniel


>   
>     ------------[ 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
>
> PATCH[1] Improves numa/test for aarch64 to follow socket-to-NUMA-node boundary
> PATCH[2] Validate the configuration if required in the NUMA subsystem
> PATCH[3] Enable the validation for aarch64 machines
> PATCH[4] Enable the validation for RiscV machines
>
> v1: https://lists.nongnu.org/archive/html/qemu-arm/2023-02/msg00886.html
>
> Changelog
> =========
> v2:
>    * Fix socket-NUMA-node boundary issues in qtests/numa-test  (Gavin)
>    * Add helper set_numa_socket_boundary() and validate the
>      boundary in the generic path                              (Philippe)
>
> Gavin Shan (4):
>    qtest/numa-test: Follow socket-NUMA-node boundary for aarch64
>    numa: Validate socket and NUMA node boundary if required
>    hw/arm: Validate socket and NUMA node boundary
>    hw/riscv: Validate socket and NUMA node boundary
>
>   hw/arm/sbsa-ref.c       |  2 ++
>   hw/arm/virt.c           |  2 ++
>   hw/core/machine.c       | 34 ++++++++++++++++++++++++++++++++++
>   hw/core/numa.c          |  7 +++++++
>   hw/riscv/spike.c        |  1 +
>   hw/riscv/virt.c         |  1 +
>   include/sysemu/numa.h   |  4 ++++
>   tests/qtest/numa-test.c | 13 ++++++++++---
>   8 files changed, 61 insertions(+), 3 deletions(-)