linux-kernel - Re: [PATCH 02/29] x86/boot/e820: Simplify e820__print

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Message-ID: <aCW-qKOYJWRLYgpx@gmail.com>
Date: Thu, 15 May 2025 12:15:04 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Mike Rapoport <rppt@...nel.org>
Cc: linux-kernel@...r.kernel.org, Andy Shevchenko <andy@...nel.org>,
	Arnd Bergmann <arnd@...nel.org>, Borislav Petkov <bp@...en8.de>,
	Juergen Gross <jgross@...e.com>, "H . Peter Anvin" <hpa@...or.com>,
	Kees Cook <keescook@...omium.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Paul Menzel <pmenzel@...gen.mpg.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	David Woodhouse <dwmw@...zon.co.uk>
Subject: Re: [PATCH 02/29] x86/boot/e820: Simplify e820__print_table() a bit


* Mike Rapoport <rppt@...nel.org> wrote:

> On Mon, Apr 21, 2025 at 08:51:42PM +0200, Ingo Molnar wrote:
> > Introduce 'entry' for the current table entry and shorten
> > repetitious use of e820_table->entries[i].
> > 
> > Signed-off-by: Ingo Molnar <mingo@...nel.org>
> > Cc: Andy Shevchenko <andy@...nel.org>
> > Cc: Arnd Bergmann <arnd@...nel.org>
> > Cc: David Woodhouse <dwmw@...zon.co.uk>
> > Cc: H. Peter Anvin <hpa@...or.com>
> > Cc: Kees Cook <keescook@...omium.org>
> > Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> > Cc: Mike Rapoport (Microsoft) <rppt@...nel.org>
> > ---
> >  arch/x86/kernel/e820.c | 8 +++++---
> >  1 file changed, 5 insertions(+), 3 deletions(-)
> > 
> > diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> > index 4a81f9e94137..b1a30bca56cd 100644
> > --- a/arch/x86/kernel/e820.c
> > +++ b/arch/x86/kernel/e820.c
> > @@ -204,12 +204,14 @@ void __init e820__print_table(char *who)
> >  	int i;
> >  
> >  	for (i = 0; i < e820_table->nr_entries; i++) {
> > +		struct e820_entry *entry = e820_table->entries + i;
> > +
> >  		pr_info("%s: [mem %#018Lx-%#018Lx] ",
> >  			who,
> > -			e820_table->entries[i].addr,
> > -			e820_table->entries[i].addr + e820_table->entries[i].size - 1);
> > +			entry->addr,
> > +			entry->addr + entry->size-1);
> 
> nit: entry->size - 1

So it's a judgement call, and here IMHO it's easier on the eyes and 
more straightforward when entry->size-1 is grouped together visually, 
which is the offset of the last byte in this E820 region.

I don't agree with the mindless conversion patches that do this 
indiscriminately:

  s/x-1
   /x - 1

Typographically and stylistically there's nothing wrong with 'x-1'.

In fact the grouping has advantages, for example this hypothethical 
buggy piece of code:

	addr_next - size-1

is much more obviously incorrect 'at a glance' during review than this 
one:

	addr_next - size - 1

Thanks,

	Ingo