linux-kernel - Re: [PATCH] crash: use macro to add crashk_res into iomem early for specific arch

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Date: Mon, 25 Mar 2024 09:42:20 +0800
From: Baoquan He <bhe@...hat.com>
To: Ingo Molnar <mingo@...nel.org>
Cc: kexec@...ts.infradead.org, linux-kernel@...r.kernel.org, x86@...nel.org,
	akpm@...ux-foundation.org, chenhuacai@...ngson.cn,
	dyoung@...hat.com, jbohac@...e.cz, lihuafei1@...wei.com,
	chenhaixiang3@...wei.com
Subject: Re: [PATCH] crash: use macro to add crashk_res into iomem early for
 specific arch

On 03/24/24 at 11:27am, Ingo Molnar wrote:
> 
> * Baoquan He <bhe@...hat.com> wrote:
> 
> > On 03/24/24 at 05:06am, Ingo Molnar wrote:
> > > 
> > > * Baoquan He <bhe@...hat.com> wrote:
> > > 
> > ......snip
> > > > ---
> > > >  arch/x86/include/asm/crash_reserve.h | 2 ++
> > > >  kernel/crash_reserve.c               | 7 +++++++
> > > >  2 files changed, 9 insertions(+)
> > > > 
> > > > diff --git a/arch/x86/include/asm/crash_reserve.h b/arch/x86/include/asm/crash_reserve.h
> > > > index 152239f95541..4681a543eba3 100644
> > > > --- a/arch/x86/include/asm/crash_reserve.h
> > > > +++ b/arch/x86/include/asm/crash_reserve.h
> > > > @@ -39,4 +39,6 @@ static inline unsigned long crash_low_size_default(void)
> > > >  #endif
> > > >  }
> > > >  
> > > > +# define HAVE_ARCH_ADD_CRASH_RES_TO_IOMEM_EARLY
> > > > +
> > > 
> > > Any reason for that stray space?
> > 
> > No clear reason. I saw stray space was added for macro definning when my
> > below patch was merged, not sure if this is preferred.
> 
> No, it's not preferred - and I don't see any stray spaces added in the 
> code added by:
> 
> > commit 85fcde402db1 ("kexec: split crashkernel reservation code out from crash_core.c")

Ah, the stray spaces are added in below macros defining, I thought they
are all the same. I didn't know nested/conditional defines and
standalone defines are different. Thanks for careful checking and telling.

arch/x86/include/asm/crash_reserve.h:
#ifdef CONFIG_X86_32
# define CRASH_ADDR_LOW_MAX     SZ_512M
# define CRASH_ADDR_HIGH_MAX    SZ_512M
#else
# define CRASH_ADDR_LOW_MAX     SZ_4G
# define CRASH_ADDR_HIGH_MAX    SZ_64T
#endif

> 
> Anyway, please just remove it.

Sure, will update and v2.

> 
> > And there are a lot of "# define " when searching with 'git grep "# 
> > define " arch/x86/include/'.
> 
> The overwhelming majority of those are not standalone defines like 
> yours, but nested/conditional defines where the space is justified:
> 
> #ifdef CONFIG_X86_32
> # define MAX_IO_APICS 64
> # define MAX_LOCAL_APIC 256
> #else
> # define MAX_IO_APICS 128
> # define MAX_LOCAL_APIC 32768
> #endif
> 
> Thanks,
> 
> 	Ingo
>