From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E785DA926 for ; Thu, 15 May 2025 11:00:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747306821; cv=none; b=LtRmtgrc6SQKOY7DUhr46QS1oI+il/SUexe3hPc+DJa5TBdGASPUBd5/CuR9EahS87/RAKi5VEsbRCFt0gIcdJbxmFOxAhu0vSHtqc8gB6HU26lLR+hN/+U5S9GmgHifqa52CUIPDpxqB6AZhOAMdOR7csLWaowws/VW2BLn2fI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747306821; c=relaxed/simple; bh=plJTIgnwLVBEUeN9TfSuX11pdlqOwA4bIN5xD+iMdg4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=hFKuCVbSuQt0XtI/qbDhAZzBnKaZm+k6M7VIc1hrE8xT+80GgAQ44JJ4NPMAv2o1cfiXs2JbImmEVXzy0lJpHDdZkzEWkwlrM2SXgXMoFWKnzw6m2vhK3tqyw2bhpW3sA8FVbOCd6GVYZCjQmnf4JpeZi/RYhXfWcagB3lFRMo8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=SRMSItB0; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="SRMSItB0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6AB18C4CEE7; Thu, 15 May 2025 11:00:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1747306819; bh=plJTIgnwLVBEUeN9TfSuX11pdlqOwA4bIN5xD+iMdg4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=SRMSItB0oRbFP5t/uJ3GQpJi7RwgFo+Ycu/8SKshQzM9doihPwuc7eJkpf36B8guo Dgj/PO5l5CGad1kveaElX2ZXggI4hUODk4oWFqXTpitpKKFYja+RCj430UUbgvXY/v YtB0guw4yhoPH7fs5NFdWTORXDlUtW6DrW1ub+OQQ5BiUJZWcKSoP4jCvbyvYRpRny AnORkdUvYXU7QsuiCYwDlq4KXvLBNcm+QyREE43mou8MY1brOyPpOp0Dk0Lsm6XXEm HjJ8fqYmj4Wj0uabLwULVaZN9mZUW/29ySVFJOwU+RlkfbXeQj3UDlZs0b9P+v/Zh1 6dI34TB7+C41Q== Date: Thu, 15 May 2025 13:00:13 +0200 From: Ingo Molnar To: Mike Rapoport Cc: linux-kernel@vger.kernel.org, Andy Shevchenko , Arnd Bergmann , Borislav Petkov , Juergen Gross , "H . Peter Anvin" , Kees Cook , Linus Torvalds , Paul Menzel , Peter Zijlstra , Thomas Gleixner , David Woodhouse Subject: Re: [PATCH 07/29] x86/boot/e820: Print out sizes of E820 memory ranges Message-ID: References: <20250421185210.3372306-1-mingo@kernel.org> <20250421185210.3372306-8-mingo@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: * Mike Rapoport wrote: > On Mon, Apr 21, 2025 at 08:51:47PM +0200, Ingo Molnar wrote: > > Before: > > > > BIOS-provided physical RAM map: > > BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable > > BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved > > BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved > > BIOS-e820: [mem 0x0000000000100000-0x000000007ffdbfff] usable > > BIOS-e820: [mem 0x000000007ffdc000-0x000000007fffffff] reserved > > BIOS-e820: [mem 0x00000000b0000000-0x00000000bfffffff] reserved > > BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed1ffff] reserved > > BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff] reserved > > BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved > > BIOS-e820: [mem 0x000000fd00000000-0x000000ffffffffff] reserved > > > > After: > > > > BIOS-provided physical RAM map: > > BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] 639 KB kernel usable RAM > > BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] 1 KB reserved > > BIOS-e820: [gap 0x00000000000a0000-0x00000000000effff] 320 KB ... > > BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] 64 KB reserved > > BIOS-e820: [mem 0x0000000000100000-0x000000007ffdbfff] 1.9 GB kernel usable RAM > > BIOS-e820: [mem 0x000000007ffdc000-0x000000007fffffff] 144 KB reserved > > BIOS-e820: [gap 0x0000000080000000-0x00000000afffffff] 768 MB ... > > BIOS-e820: [mem 0x00000000b0000000-0x00000000bfffffff] 256 MB reserved > > BIOS-e820: [gap 0x00000000c0000000-0x00000000fed1bfff] 1005.1 MB ... > > BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed1ffff] 16 KB reserved > > BIOS-e820: [gap 0x00000000fed20000-0x00000000feffbfff] 2.8 MB ... > > BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff] 16 KB reserved > > BIOS-e820: [gap 0x00000000ff000000-0x00000000fffbffff] 15.7 MB ... > > BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] 256 KB reserved > > BIOS-e820: [gap 0x0000000100000000-0x000000fcffffffff] 1008 GB ... > > BIOS-e820: [mem 0x000000fd00000000-0x000000ffffffffff] 12 GB reserved > > > > Note how a 1-digit precision field is printed out if a range is > > fractional in its largest-enclosing natural size unit. > > > > So the "256 MB" and "12 GB" fields above denote exactly 256 MB and > > 12 GB regions, while "1.9 GB" signals the region's fractional nature > > and it being just below 2GB. > > > > Printing E820 maps with such details visualizes 'weird' ranges > > at a glance, and gives users a better understanding of how > > large the various ranges are, without having to perform hexadecimal > > subtraction in their minds. > > > > Signed-off-by: Ingo Molnar > > Cc: Andy Shevchenko > > Cc: Arnd Bergmann > > Cc: David Woodhouse > > Cc: H. Peter Anvin > > Cc: Kees Cook > > Cc: Linus Torvalds > > Cc: Mike Rapoport (Microsoft) > > (cherry picked from commit d1ac6b8718575a7ea2f0a1ff347835a8879df673) > > --- > > arch/x86/kernel/e820.c | 47 +++++++++++++++++++++++++++++++++++++++++++++-- > > 1 file changed, 45 insertions(+), 2 deletions(-) > > > > diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c > > index 10bd10bd5672..8ee89962fcbf 100644 > > --- a/arch/x86/kernel/e820.c > > +++ b/arch/x86/kernel/e820.c > > @@ -199,6 +199,41 @@ static void __init e820_print_type(enum e820_type type) > > } > > } > > > > +/* > > + * Print out the size of a E820 region, in human-readable > > + * fashion, going from KB, MB, GB to TB units. > > + * > > + * Print out fractional sizes with a single digit of precision. > > + */ > > +static void e820_print_size(u64 size) > > +{ > > + if (size < SZ_1M) { > > + if (size & (SZ_1K-1)) > > + pr_cont(" %4llu.%01llu KB", size/SZ_1K, 10*(size & (SZ_1K-1))/SZ_1K); > > + else > > + pr_cont(" %4llu KB", size/SZ_1K); > > + return; > > + } > > I'd make this a helper, e.g > > static void __e820_print_size(u64 size, u64 unit, const char *unit_name) > { > if (size & (unit - 1)) { > u64 fraction = 10 * (size & (unit - 1))/unit; > > pr_cont(" %4llu.%01llu %s", size/unit, fraction, unit_name); > } else { > pr_cont(" %4llu %s", size/unit, unit_name); > } > } While I like the helper in principle, it doesn't work on 32-bit: it's an u64 with u64 division, while with the open coded literals the compiler figures it out. With div64_u64(), or a macro, it's not nearly as obvious a cleanup IMHO. Thanks, Ingo