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

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Date:   Thu, 24 Aug 2023 08:59:23 -0700
From:   Saurabh Singh Sengar <ssengar@...ux.microsoft.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     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
Subject: Re: [PATCH] x86/numa: Add Devicetree support

On Thu, Aug 24, 2023 at 05:28:37PM +0200, Thomas Gleixner wrote:
> 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 for the review, I will send the v2 with suggested modifications.

- Saurabh

> 
> Thanks,
> 
>         tglx
> 
> 
> 
>