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Re: [PATCH v3 2/4] hw/arm/virt: Fix CPU's default NUMA node ID
From: |
Igor Mammedov |
Subject: |
Re: [PATCH v3 2/4] hw/arm/virt: Fix CPU's default NUMA node ID |
Date: |
Fri, 25 Mar 2022 14:25:17 +0100 |
On Wed, 23 Mar 2022 15:24:36 +0800
Gavin Shan <gshan@redhat.com> wrote:
> When CPU-to-NUMA association isn't explicitly provided by users,
> the default on is given by mc->get_default_cpu_node_id(). However,
> the CPU topology isn't fully considered in the default association
> and this causes CPU topology broken warnings on booting Linux guest.
>
> For example, the following warning messages are observed when the
> Linux guest is booted with the following command lines.
>
> /home/gavin/sandbox/qemu.main/build/qemu-system-aarch64 \
> -accel kvm -machine virt,gic-version=host \
> -cpu host \
> -smp 6,sockets=2,cores=3,threads=1 \
> -m 1024M,slots=16,maxmem=64G \
> -object memory-backend-ram,id=mem0,size=128M \
> -object memory-backend-ram,id=mem1,size=128M \
> -object memory-backend-ram,id=mem2,size=128M \
> -object memory-backend-ram,id=mem3,size=128M \
> -object memory-backend-ram,id=mem4,size=128M \
> -object memory-backend-ram,id=mem4,size=384M \
> -numa node,nodeid=0,memdev=mem0 \
> -numa node,nodeid=1,memdev=mem1 \
> -numa node,nodeid=2,memdev=mem2 \
> -numa node,nodeid=3,memdev=mem3 \
> -numa node,nodeid=4,memdev=mem4 \
> -numa node,nodeid=5,memdev=mem5
> :
> alternatives: patching kernel code
> BUG: arch topology borken
> the CLS domain not a subset of the MC domain
> <the above error log repeats>
> BUG: arch topology borken
> the DIE domain not a subset of the NODE domain
>
> With current implementation of mc->get_default_cpu_node_id(),
> CPU#0 to CPU#5 are associated with NODE#0 to NODE#5 separately.
> That's incorrect because CPU#0/1/2 should be associated with same
> NUMA node because they're seated in same socket.
>
> This fixes the issue by considering the socket ID when the default
> CPU-to-NUMA association is provided in virt_possible_cpu_arch_ids().
> With this applied, no more CPU topology broken warnings are seen
> from the Linux guest. The 6 CPUs are associated with NODE#0/1, but
> there are no CPUs associated with NODE#2/3/4/5.
>
> Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
> ---
> hw/arm/virt.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index 064eac42f7..3286915229 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -2497,7 +2497,9 @@ virt_cpu_index_to_props(MachineState *ms, unsigned
> cpu_index)
>
> static int64_t virt_get_default_cpu_node_id(const MachineState *ms, int idx)
> {
> - return idx % ms->numa_state->num_nodes;
> + int64_t socket_id = ms->possible_cpus->cpus[idx].props.socket_id;
> +
> + return socket_id % ms->numa_state->num_nodes;
> }
>
> static const CPUArchIdList *virt_possible_cpu_arch_ids(MachineState *ms)