linux-kernel - Re: [PATCH 20/32] x86/boot/e820: Clean up e820__setup_pci_gap()/e820_search

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Message-ID: <f77eaadc-b458-4d3d-bf31-0fef6d9d8ca3@suse.com>
Date: Mon, 2 Jun 2025 15:41:24 +0300
From: Nikolay Borisov <nik.borisov@...e.com>
To: Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org
Cc: 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>,
 Mike Rapoport <rppt@...nel.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 20/32] x86/boot/e820: Clean up
 e820__setup_pci_gap()/e820_search_gap() a bit



On 5/15/25 15:05, Ingo Molnar wrote:
> Apply misc cleanups:
> 
>   - Use a bit more readable variable names, we haven't run out of
>     underscore characters in the kernel yet.
> 
>   - s/0x400000/SZ_4M
> 
>   - s/1024*1024/SZ_1M
> 
> Suggested-by: Andy Shevchenko <andy@...nel.org>
> Signed-off-by: Ingo Molnar <mingo@...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 | 22 +++++++++++-----------
>   1 file changed, 11 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> index ee8b56605e4a..d00ca2dd20b7 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -680,7 +680,7 @@ static void __init e820__update_table_kexec(void)
>   /*
>    * Search for a gap in the E820 memory space from 0 to MAX_GAP_END (4GB).
>    */
> -static int __init e820_search_gap(unsigned long *gapstart, unsigned long *gapsize)
> +static int __init e820_search_gap(unsigned long *gap_start, unsigned long *gap_size)
>   {
>   	u64 last = MAX_GAP_END;
>   	int idx = e820_table->nr_entries;
> @@ -697,9 +697,9 @@ static int __init e820_search_gap(unsigned long *gapstart, unsigned long *gapsiz
>   		if (last > end) {
>   			unsigned long gap = last - end;
>   
> -			if (gap >= *gapsize) {
> -				*gapsize = gap;
> -				*gapstart = end;
> +			if (gap >= *gap_size) {
> +				*gap_size = gap;
> +				*gap_start = end;
>   				found = 1;
>   			}
>   		}
> @@ -719,29 +719,29 @@ static int __init e820_search_gap(unsigned long *gapstart, unsigned long *gapsiz
>    */
>   __init void e820__setup_pci_gap(void)
>   {
> -	unsigned long gapstart, gapsize;
> +	unsigned long gap_start, gap_size;
>   	int found;
>   
> -	gapsize = 0x400000;
> -	found  = e820_search_gap(&gapstart, &gapsize);
> +	gap_size = SZ_4M;
> +	found  = e820_search_gap(&gap_start, &gap_size);
>   
>   	if (!found) {
>   #ifdef CONFIG_X86_64
> -		gapstart = (max_pfn << PAGE_SHIFT) + 1024*1024;
> +		gap_start = (max_pfn << PAGE_SHIFT) + SZ_1M;
>   		pr_err("Cannot find an available gap in the 32-bit address range\n");
>   		pr_err("PCI devices with unassigned 32-bit BARs may not work!\n");
>   #else
> -		gapstart = 0x10000000;
> +		gap_start = 0x10000000;

nit: gap_start = SZ_256M;

>   #endif
>   	}
>   
>   	/*
>   	 * e820__reserve_resources_late() protects stolen RAM already:
>   	 */
> -	pci_mem_start = gapstart;
> +	pci_mem_start = gap_start;
>   
>   	pr_info("[gap %#010lx-%#010lx] available for PCI devices\n",
> -		gapstart, gapstart + gapsize - 1);
> +		gap_start, gap_start + gap_size - 1);
>   }
>   
>   /*