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Re: [PATCH 1/2] hw/386: Fix uninitialized memory with -device and CPU ho
From: |
Igor Mammedov |
Subject: |
Re: [PATCH 1/2] hw/386: Fix uninitialized memory with -device and CPU hotplug |
Date: |
Tue, 16 Jun 2020 12:59:01 +0200 |
On Mon, 08 Jun 2020 15:18:50 -0500
Babu Moger <babu.moger@amd.com> wrote:
> Noticed the following command failure while testing CPU hotplug.
>
> $ qemu-system-x86_64 -machine q35,accel=kvm -smp 1,maxcpus=2,
> cores=1, threads=1,sockets=2 -cpu EPYC -device EPYC-x86_64-
> cpu,core-id=0,socket-id=1,thread-id=0
>
> qemu-system-x86_64: -device EPYC-x86_64-cpu,core-id=0,socket-id=1,
> thread-id=0: Invalid CPU [socket: 21855, die: 0, core: 0, thread: 0]
> with APIC ID 21855, valid index range 0:1
>
> This happens because APIC ID is calculated using uninitialized memory.
> This is happening after the addition of new field node_id in X86CPUTopoIDs
> structure. The node_id field is uninitialized while calling
> apicid_from_topo_ids. The problem is discussed in the thread below.
> 20200602171838.GG577771@habkost.net/">https://lore.kernel.org/qemu-devel/20200602171838.GG577771@habkost.net/
>
> Fix the problem by initializing the node_id properly.
>
> Signed-off-by: Babu Moger <babu.moger@amd.com>
> ---
> hw/i386/pc.c | 2 ++
> include/hw/i386/topology.h | 11 +++++++++++
> 2 files changed, 13 insertions(+)
>
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index 2128f3d6fe..974cc30891 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -1585,6 +1585,8 @@ static void pc_cpu_pre_plug(HotplugHandler *hotplug_dev,
> topo_ids.die_id = cpu->die_id;
> topo_ids.core_id = cpu->core_id;
> topo_ids.smt_id = cpu->thread_id;
> + topo_ids.node_id = cpu_x86_use_epyc_apic_id_encoding(ms->cpu_type) ?
> + x86_node_id_for_epyc(&topo_info, &topo_ids) : 0;
I'd rather not calculate some default value here,
this is the branch where we check user provided topology info and error out
asking
to provide missing bits.
I also wonder if we should force user to specify numa nodes on CLI if EPYC cpu
is used.
(i.e. I'm assuming that EPYC always requires numa)
> cpu->apic_id = x86ms->apicid_from_topo_ids(&topo_info, &topo_ids);
> }
>
> diff --git a/include/hw/i386/topology.h b/include/hw/i386/topology.h
> index 07239f95f4..ee4deb84c4 100644
> --- a/include/hw/i386/topology.h
> +++ b/include/hw/i386/topology.h
> @@ -140,6 +140,17 @@ static inline unsigned
> apicid_pkg_offset_epyc(X86CPUTopoInfo *topo_info)
> apicid_node_width_epyc(topo_info);
> }
>
> +static inline unsigned x86_node_id_for_epyc(X86CPUTopoInfo *topo_info,
> + const X86CPUTopoIDs *topo_ids)
> +{
> + unsigned nr_nodes = MAX(topo_info->nodes_per_pkg, 1);
> + unsigned cores_per_node = DIV_ROUND_UP((topo_info->dies_per_pkg *
> + topo_info->cores_per_die *
> + topo_info->threads_per_core),
> + nr_nodes);
> +
> + return (topo_ids->core_id / cores_per_node) % nr_nodes;
what if nr_nodes == 0?
> +}
> /*
> * Make APIC ID for the CPU based on Pkg_ID, Core_ID, SMT_ID
> *
>
>
- [PATCH 0/2] Fix couple of issues with AMD topology, Babu Moger, 2020/06/08
- [PATCH 2/2] i386: Simplify CPUID_8000_001E for AMD, Babu Moger, 2020/06/08
- [PATCH 1/2] hw/386: Fix uninitialized memory with -device and CPU hotplug, Babu Moger, 2020/06/08
- Re: [PATCH 1/2] hw/386: Fix uninitialized memory with -device and CPU hotplug,
Igor Mammedov <=
- RE: [PATCH 1/2] hw/386: Fix uninitialized memory with -device and CPU hotplug, Babu Moger, 2020/06/16
- Re: [PATCH 1/2] hw/386: Fix uninitialized memory with -device and CPU hotplug, Igor Mammedov, 2020/06/24
- RE: [PATCH 1/2] hw/386: Fix uninitialized memory with -device and CPU hotplug, Babu Moger, 2020/06/24
- Re: [PATCH 1/2] hw/386: Fix uninitialized memory with -device and CPU hotplug, Igor Mammedov, 2020/06/25
- RE: [PATCH 1/2] hw/386: Fix uninitialized memory with -device and CPU hotplug, Babu Moger, 2020/06/25
- Re: [PATCH 1/2] hw/386: Fix uninitialized memory with -device and CPU hotplug, Igor Mammedov, 2020/06/25
- Re: [PATCH 1/2] hw/386: Fix uninitialized memory with -device and CPU hotplug, Babu Moger, 2020/06/25
- RE: [PATCH 1/2] hw/386: Fix uninitialized memory with -device and CPU hotplug, Babu Moger, 2020/06/26
- RE: [PATCH 1/2] hw/386: Fix uninitialized memory with -device and CPU hotplug, Babu Moger, 2020/06/29