linux-kernel - Re: [PATCH 2/5] arm64: kdump: Support crashkernel=X fall back to reserve region above DMA zones

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Message-ID: <20220617041633.GD234358@MiWiFi-R3L-srv>
Date:   Fri, 17 Jun 2022 12:16:33 +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 2/5] arm64: kdump: Support crashkernel=X fall back to
 reserve region above DMA zones

On 06/13/22 at 04:09pm, Zhen Lei wrote:
> For crashkernel=X without '@...set', select a region within DMA zones
> first, and fall back to reserve region above DMA zones. This allows
> users to use the same configuration on multiple platforms.

LGTM,

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

> 
> Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
> ---
>  Documentation/admin-guide/kernel-parameters.txt |  2 +-
>  arch/arm64/mm/init.c                            | 16 +++++++++++++++-
>  2 files changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 61b179232b68001..fdac18beba5624e 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -823,7 +823,7 @@
>  			memory region [offset, offset + size] for that kernel
>  			image. If '@...set' is omitted, then a suitable offset
>  			is selected automatically.
> -			[KNL, X86-64] Select a region under 4G first, and
> +			[KNL, X86-64, ARM64] Select a region under 4G first, and
>  			fall back to reserve region above 4G when '@...set'
>  			hasn't been specified.
>  			See Documentation/admin-guide/kdump/kdump.rst for further details.
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 5390f361208ccf7..8539598f9e58b4d 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -138,6 +138,7 @@ static void __init reserve_crashkernel(void)
>  	unsigned long long crash_max = CRASH_ADDR_LOW_MAX;
>  	char *cmdline = boot_command_line;
>  	int ret;
> +	bool fixed_base;
>  
>  	if (!IS_ENABLED(CONFIG_KEXEC_CORE))
>  		return;
> @@ -166,15 +167,28 @@ static void __init reserve_crashkernel(void)
>  		return;
>  	}
>  
> +	fixed_base = !!crash_base;
>  	crash_size = PAGE_ALIGN(crash_size);
>  
>  	/* User specifies base address explicitly. */
> -	if (crash_base)
> +	if (fixed_base)
>  		crash_max = crash_base + crash_size;
>  
> +retry:
>  	crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN,
>  					       crash_base, crash_max);
>  	if (!crash_base) {
> +		/*
> +		 * Attempt to fully allocate low memory failed, fall back
> +		 * to high memory, the minimum required low memory will be
> +		 * reserved later.
> +		 */
> +		if (!fixed_base && (crash_max == CRASH_ADDR_LOW_MAX)) {
> +			crash_max = CRASH_ADDR_HIGH_MAX;
> +			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
> +			goto retry;
> +		}
> +
>  		pr_warn("cannot allocate crashkernel (size:0x%llx)\n",
>  			crash_size);
>  		return;
> -- 
> 2.25.1
>