linux-kernel - Re: [PATCH] x86/numa: Add Devicetree support

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Date:   Thu, 24 Aug 2023 17:28:37 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Saurabh Sengar <ssengar@...ux.microsoft.com>, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org,
        hpa@...or.com, luto@...nel.org, peterz@...radead.org,
        mikelley@...rosoft.com, linux-kernel@...r.kernel.org
Cc:     ssengar@...ux.microsoft.com
Subject: Re: [PATCH] x86/numa: Add Devicetree support

On Tue, Jun 27 2023 at 00:28, Saurabh Sengar wrote:
> Hyper-V has usecases where it need to fetch NUMA information from
> Devicetree. Currently, it is not possible to extract the NUMA
> information from Devicetree for x86 arch.
>
> Add support for Devicetree in the x86_numa_init function, allowing
> the retrieval of NUMA node information from the Devicetree.
>
> Additionally, relocate the x86_dtb_init function before initmem_init
> to ensure the Devicetree initialization prior to its utilization in
> x86_numa_init.

Moving dtb_init() is not really a good idea. The APIC/IO-APIC
enumeration is post initmem_init() on purpose and the ongoing rework of
the topology evaluation relies on that.

What you really want is to split dtb_init() into two parts:

   1) x86_flattree_get_config() which can be invoked before initmem init
      like ACPI has an early init part so SRAT parsing can be done in
      the numa initialization.

   2) The APIC/IOAPIC registration part, which stays where it is.

This split wants to be a seperate change.

Thanks,

        tglx