linux-kernel - Re: [PATCH v9 11/12] target/arm: add an experimental mpidr arm cpu property object

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Message-ID: <CAFEAcA-OaQ1ypa7LXz5nOs+6+fjmYNHzNL0VVgapoXEHU=rHnQ@mail.gmail.com>
Date: Sun, 25 Aug 2024 12:34:14 +0100
From: Peter Maydell <peter.maydell@...aro.org>
To: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Cc: linux-kernel@...r.kernel.org, qemu-arm@...gnu.org, qemu-devel@...gnu.org
Subject: Re: [PATCH v9 11/12] target/arm: add an experimental mpidr arm cpu
 property object

On Sun, 25 Aug 2024 at 04:46, Mauro Carvalho Chehab
<mchehab+huawei@...nel.org> wrote:
>
> Accurately injecting an ARM Processor error ACPI/APEI GHES
> error record requires the value of the ARM Multiprocessor
> Affinity Register (mpidr).
>
> While ARM implements it, this is currently not visible.
>
> Add a field at CPU storing it, and place it at arm_cpu_properties
> as experimental, thus allowing it to be queried via QMP using
> qom-get function.

>  static Property arm_cpu_properties[] = {
>      DEFINE_PROP_UINT64("midr", ARMCPU, midr, 0),
> +    DEFINE_PROP_UINT64("x-mpidr", ARMCPU, mpidr, 0),
>      DEFINE_PROP_UINT64("mp-affinity", ARMCPU,
>                          mp_affinity, ARM64_AFFINITY_INVALID),
>      DEFINE_PROP_INT32("node-id", ARMCPU, node_id, CPU_UNSET_NUMA_NODE_ID),

Why do we need this? Why is it experimental? The later patch
seems to use it via QMP, which I'm not super enthusiastic
about -- the preexisting mpidr and mp-affinity properties are
there for code that is creating CPU objects to configure
the CPU object, not as a query interface for QOM.

thanks
-- PMM