linux-kernel - Re: [PATCH v2 1/2] x86/of: split x86_dtb_init for early x86_flattree_get

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Date:   Thu, 14 Sep 2023 22:03:33 -0700
From:   Saurabh Singh Sengar <ssengar@...ux.microsoft.com>
To:     tglx@...utronix.de, 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 v2 1/2] x86/of: split x86_dtb_init for early
 x86_flattree_get_config call

On Fri, Aug 25, 2023 at 12:47:36AM -0700, Saurabh Sengar wrote:
> Fetching the device tree configuration before initmem_init is necessary
> to allow the parsing of NUMA node information. However moving entire
> x86_dtb_init before initmem_init is not correct as APIC/IO-APIC enumeration
> has to be after initmem_init. Thus, split the x86_dtb_init function to
> incorporate a call to x86_flattree_get_config before initmem_init, and
> leaving the ACPI/IOAPIC registration sequence as is.
> 
> Signed-off-by: Saurabh Sengar <ssengar@...ux.microsoft.com>
> ---
> [V2]
>  - split the x86_dtb_init to call x86_flattree_get_config early
> 
>  arch/x86/include/asm/prom.h  | 5 +++++
>  arch/x86/kernel/devicetree.c | 6 +-----
>  arch/x86/kernel/setup.c      | 2 ++
>  3 files changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/include/asm/prom.h b/arch/x86/include/asm/prom.h
> index b716d291d0d4..65dee2420624 100644
> --- a/arch/x86/include/asm/prom.h
> +++ b/arch/x86/include/asm/prom.h
> @@ -31,6 +31,11 @@ static inline void x86_dtb_init(void) { }
>  #define of_ioapic 0
>  #endif
>  
> +#ifdef CONFIG_OF_EARLY_FLATTREE
> +void x86_flattree_get_config(void);
> +#else
> +static inline void x86_flattree_get_config(void) { }
> +#endif
>  extern char cmd_line[COMMAND_LINE_SIZE];
>  
>  #endif /* __ASSEMBLY__ */
> diff --git a/arch/x86/kernel/devicetree.c b/arch/x86/kernel/devicetree.c
> index 87d38f17ff5c..afd09924094e 100644
> --- a/arch/x86/kernel/devicetree.c
> +++ b/arch/x86/kernel/devicetree.c
> @@ -278,7 +278,7 @@ static void __init dtb_apic_setup(void)
>  }
>  
>  #ifdef CONFIG_OF_EARLY_FLATTREE
> -static void __init x86_flattree_get_config(void)
> +void __init x86_flattree_get_config(void)
>  {
>  	u32 size, map_len;
>  	void *dt;
> @@ -300,14 +300,10 @@ static void __init x86_flattree_get_config(void)
>  	unflatten_and_copy_device_tree();
>  	early_memunmap(dt, map_len);
>  }
> -#else
> -static inline void x86_flattree_get_config(void) { }
>  #endif
>  
>  void __init x86_dtb_init(void)
>  {
> -	x86_flattree_get_config();
> -
>  	if (!of_have_populated_dt())
>  		return;
>  
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index b9145a63da77..ef73704fa27f 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -1221,6 +1221,8 @@ void __init setup_arch(char **cmdline_p)
>  
>  	early_acpi_boot_init();
>  
> +	x86_flattree_get_config();
> +
>  	initmem_init();
>  	dma_contiguous_reserve(max_pfn_mapped << PAGE_SHIFT);
>  
> -- 
> 2.34.1

Kind reminder to review this patch series.

- Saurabh