linux-kernel - Re: [PATCH 4/4] x86/efi: print size and base in binary units in efi_print

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Date:	Mon, 21 Dec 2015 16:16:29 +0000
From:	Matt Fleming <matt@...eblueprint.co.uk>
To:	Robert Elliott <elliott@....com>
Cc:	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	x86@...nel.org, linux-efi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] x86/efi: print size and base in binary units in
 efi_print_memmap

On Thu, 17 Dec, at 07:28:34PM, Robert Elliott wrote:
> Print the base address for each range in decimal alongside the size.
> Use a "(size @ base)" format similar to the fake_memmap kernel parameter.
> 
> Print the range and base in the best-fit B, KiB, MiB, etc. units rather
> than always MiB.  This avoids rounding, which can be misleading.
> 
> Use proper IEC binary units (KiB, MiB, etc.) rather than misuse SI
> decimal units (KB, MB, etc.).
> 
> old:
>     efi: mem61: [Persistent Memory  |   |  |  |  |  |  |   |WB|WT|WC|UC] range=[0x0000000880000000-0x0000000c7fffffff) (16384MB)
> 
> new:
>     efi: mem61: [Persistent Memory  |   |  |  |  |  |  |   |WB|WT|WC|UC] range=[0x0000000880000000-0x0000000c7fffffff] (16 GiB @ 34 GiB)
> 
> Signed-off-by: Robert Elliott <elliott@....com>
> ---
>  arch/x86/platform/efi/efi.c | 27 ++++++++++++++++++++++++---
>  1 file changed, 24 insertions(+), 3 deletions(-)
 
I'm not at all sure of the value of printing the physical address as a
size. I would have thought that you'd have to convert it back to an
address whenever you wanted to use it anyway.

> diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
> index 635a955..030ba91 100644
> --- a/arch/x86/platform/efi/efi.c
> +++ b/arch/x86/platform/efi/efi.c
> @@ -222,6 +222,25 @@ int __init efi_memblock_x86_reserve_range(void)
>  	return 0;
>  }
>  
> +char * __init efi_size_format(char *buf, size_t size, u64 bytes)
> +{
> +	if (!bytes || (bytes & 0x3ff))
> +		snprintf(buf, size, "%llu B", bytes);
> +	else if (bytes & 0xfffff)
> +		snprintf(buf, size, "%llu KiB", bytes >> 10);
> +	else if (bytes & 0x3fffffff)
> +		snprintf(buf, size, "%llu MiB", bytes >> 20);
> +	else if (bytes & 0xffffffffff)
> +		snprintf(buf, size, "%llu GiB", bytes >> 30);
> +	else if (bytes & 0x3ffffffffffff)
> +		snprintf(buf, size, "%llu TiB", bytes >> 40);
> +	else if (bytes & 0xfffffffffffffff)
> +		snprintf(buf, size, "%llu PiB", bytes >> 50);
> +	else
> +		snprintf(buf, size, "%llu EiB", bytes >> 60);
> +	return buf;
> +}
> +

Can we use string_get_size() instead of rolling our own function?
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