linux-kernel - Re: [PATCH v2 3/7] x86/of: Unconditionally call unflatten_and_copy_device

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Date: Tue, 30 Jan 2024 05:30:39 -0800
From: Saurabh Singh Sengar <ssengar@...ux.microsoft.com>
To: Stephen Boyd <sboyd@...nel.org>
Cc: Rob Herring <robh+dt@...nel.org>, linux-kernel@...r.kernel.org,
	patches@...ts.linux.dev, linux-um@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, kunit-dev@...glegroups.com,
	linux-kselftest@...r.kernel.org, devicetree@...r.kernel.org,
	Frank Rowand <frowand.list@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v2 3/7] x86/of: Unconditionally call
 unflatten_and_copy_device_tree()

On Mon, Jan 29, 2024 at 04:45:02PM -0800, Stephen Boyd wrote:
> Call this function unconditionally so that we can populate an empty DTB
> on platforms that don't boot with a firmware provided or builtin DTB.
> 
> Cc: Rob Herring <robh+dt@...nel.org>
> Cc: Frank Rowand <frowand.list@...il.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: <x86@...nel.org>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: Saurabh Sengar <ssengar@...ux.microsoft.com>
> Signed-off-by: Stephen Boyd <sboyd@...nel.org>
> ---
>  arch/x86/kernel/devicetree.c | 24 +++++++++++++-----------
>  1 file changed, 13 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/x86/kernel/devicetree.c b/arch/x86/kernel/devicetree.c
> index afd09924094e..650752d112a6 100644
> --- a/arch/x86/kernel/devicetree.c
> +++ b/arch/x86/kernel/devicetree.c
> @@ -283,22 +283,24 @@ void __init x86_flattree_get_config(void)
>  	u32 size, map_len;
>  	void *dt;
>  
> -	if (!initial_dtb)
> -		return;
> +	if (initial_dtb) {
> +		map_len = max(PAGE_SIZE - (initial_dtb & ~PAGE_MASK), (u64)128);
>  
> -	map_len = max(PAGE_SIZE - (initial_dtb & ~PAGE_MASK), (u64)128);
> +		dt = early_memremap(initial_dtb, map_len);
> +		size = fdt_totalsize(dt);
> +		if (map_len < size) {
> +			early_memunmap(dt, map_len);
> +			dt = early_memremap(initial_dtb, size);
> +			map_len = size;
> +		}
>  
> -	dt = early_memremap(initial_dtb, map_len);
> -	size = fdt_totalsize(dt);
> -	if (map_len < size) {
> -		early_memunmap(dt, map_len);
> -		dt = early_memremap(initial_dtb, size);
> -		map_len = size;
> +		early_init_dt_verify(dt);
>  	}
>  
> -	early_init_dt_verify(dt);
>  	unflatten_and_copy_device_tree();
> -	early_memunmap(dt, map_len);
> +
> +	if (initial_dtb)
> +		early_memunmap(dt, map_len);
>  }
>  #endif
>  
> -- 
> https://git.kernel.org/pub/scm/linux/kernel/git/clk/linux.git/
> https://git.kernel.org/pub/scm/linux/kernel/git/sboyd/spmi.git


Tested the series in Hyper-V environment. Please feel free to add:
Tested-by: Saurabh Sengar <ssengar@...ux.microsoft.com>