linux-kernel - Re: [PATCH 3/3] arm64: kdump: defer the crashkernel reservation for platforms with no DMA memory zones

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Date:   Sat, 25 Mar 2023 10:04:33 +0800
From:   "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
To:     Baoquan He <bhe@...hat.com>, <linux-kernel@...r.kernel.org>
CC:     <catalin.marinas@....com>, <horms@...nel.org>,
        <John.p.donnelly@...cle.com>, <will@...nel.org>,
        <kexec@...ts.infradead.org>, <ardb@...nel.org>, <rppt@...nel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 3/3] arm64: kdump: defer the crashkernel reservation for
 platforms with no DMA memory zones



On 2023/3/24 21:18, Baoquan He wrote:
> In commit 031495635b46 ("arm64: Do not defer reserve_crashkernel() for
> platforms with no DMA memory zones"), reserve_crashkernel() is called
> much earlier in arm64_memblock_init() to avoid causing base apge
> mapping on platforms with no DMA meomry zones.
> 
> With taking off protection on crashkernel memory region, no need to call
> reserve_crashkernel() specially in advance. The deferred invocation of
> reserve_crashkernel() in bootmem_init() can cover all cases.
> 
> Signed-off-by: Baoquan He <bhe@...hat.com>
> ---
>  arch/arm64/include/asm/memory.h | 5 -----
>  arch/arm64/mm/init.c            | 6 +-----
>  2 files changed, 1 insertion(+), 10 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
> index 78e5163836a0..efcd68154a3a 100644
> --- a/arch/arm64/include/asm/memory.h
> +++ b/arch/arm64/include/asm/memory.h
> @@ -374,11 +374,6 @@ static inline void *phys_to_virt(phys_addr_t x)
>  })
>  
>  void dump_mem_limit(void);
> -
> -static inline bool defer_reserve_crashkernel(void)
> -{
> -	return IS_ENABLED(CONFIG_ZONE_DMA) || IS_ENABLED(CONFIG_ZONE_DMA32);
> -}
>  #endif /* !ASSEMBLY */
>  
>  /*
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 58a0bb2c17f1..b888de59e0b7 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -408,9 +408,6 @@ void __init arm64_memblock_init(void)
>  
>  	early_init_fdt_scan_reserved_mem();
>  
> -	if (!defer_reserve_crashkernel())
> -		reserve_crashkernel();
> -
>  	high_memory = __va(memblock_end_of_DRAM() - 1) + 1;
>  }
>  
> @@ -457,8 +454,7 @@ void __init bootmem_init(void)
>  	 * request_standard_resources() depends on crashkernel's memory being
>  	 * reserved, so do it here.
>  	 */
> -	if (defer_reserve_crashkernel())
> -		reserve_crashkernel();
> +	reserve_crashkernel();
>  
>  	memblock_dump_all();
>  }

Some comments also need to be deleted, above the definition of arm64_dma_phys_limit
in arch/arm64/mm/init.c

> 

-- 
Regards,
  Zhen Lei