linux-kernel - Re: [PATCH 3/5] arm64: kdump: Remove some redundant checks in map

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Date:   Mon, 20 Jun 2022 15:42:58 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Zhen Lei <thunder.leizhen@...wei.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H . Peter Anvin" <hpa@...or.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        devicetree@...r.kernel.org, Dave Young <dyoung@...hat.com>,
        Vivek Goyal <vgoyal@...hat.com>, kexec@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
        Randy Dunlap <rdunlap@...radead.org>,
        Feng Zhou <zhoufeng.zf@...edance.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Chen Zhou <dingguo.cz@...group.com>,
        John Donnelly <John.p.donnelly@...cle.com>,
        Dave Kleikamp <dave.kleikamp@...cle.com>
Subject: Re: [PATCH 3/5] arm64: kdump: Remove some redundant checks in
 map_mem()

On 06/13/22 at 04:09pm, Zhen Lei wrote:
> arm64_memblock_init()
> 	if (!IS_ENABLED(CONFIG_ZONE_DMA/DMA32))
> 		reserve_crashkernel()
> 			//initialize crashk_res when
> 			//"crashkernel=" is correctly specified
> paging_init()
> 	map_mem()
> 
> As shown in the above pseudo code, the crashk_res.end can only be
> initialized to non-zero when both "!IS_ENABLED(CONFIG_ZONE_DMA/DMA32)"
> and crash_mem_map are true. So some checks in map_mem() can be adjusted
> or optimized.

LGTM,

Acked-by: Baoquan He <bhe@...hat.com>

> 
> Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
> ---
>  arch/arm64/mm/mmu.c | 25 +++++++++++--------------
>  1 file changed, 11 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 626ec32873c6c36..6028a5757e4eae2 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -529,12 +529,12 @@ static void __init map_mem(pgd_t *pgdp)
>  
>  #ifdef CONFIG_KEXEC_CORE
>  	if (crash_mem_map) {
> -		if (IS_ENABLED(CONFIG_ZONE_DMA) ||
> -		    IS_ENABLED(CONFIG_ZONE_DMA32))
> -			flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
> -		else if (crashk_res.end)
> +		if (crashk_res.end)
>  			memblock_mark_nomap(crashk_res.start,
>  			    resource_size(&crashk_res));
> +		else if (IS_ENABLED(CONFIG_ZONE_DMA) ||
> +			 IS_ENABLED(CONFIG_ZONE_DMA32))
> +			flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
>  	}
>  #endif
>  
> @@ -571,16 +571,13 @@ static void __init map_mem(pgd_t *pgdp)
>  	 * through /sys/kernel/kexec_crash_size interface.
>  	 */
>  #ifdef CONFIG_KEXEC_CORE
> -	if (crash_mem_map &&
> -	    !IS_ENABLED(CONFIG_ZONE_DMA) && !IS_ENABLED(CONFIG_ZONE_DMA32)) {
> -		if (crashk_res.end) {
> -			__map_memblock(pgdp, crashk_res.start,
> -				       crashk_res.end + 1,
> -				       PAGE_KERNEL,
> -				       NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS);
> -			memblock_clear_nomap(crashk_res.start,
> -					     resource_size(&crashk_res));
> -		}
> +	if (crashk_res.end) {
> +		__map_memblock(pgdp, crashk_res.start,
> +			       crashk_res.end + 1,
> +			       PAGE_KERNEL,
> +			       NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS);
> +		memblock_clear_nomap(crashk_res.start,
> +				     resource_size(&crashk_res));
>  	}
>  #endif
>  }
> -- 
> 2.25.1
>