linux-kernel - Re: [PATCH v17 03/10] x86: kdump: use macro CRASH_ADDR_LOW_MAX in functions reserve

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Date:   Mon, 13 Dec 2021 08:28:14 -0600
From:   john.p.donnelly@...cle.com
To:     Zhen Lei <thunder.leizhen@...wei.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H . Peter Anvin" <hpa@...or.com>,
        linux-kernel@...r.kernel.org, Dave Young <dyoung@...hat.com>,
        Baoquan He <bhe@...hat.com>, Vivek Goyal <vgoyal@...hat.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        kexec@...ts.infradead.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        devicetree@...r.kernel.org, Jonathan Corbet <corbet@....net>,
        linux-doc@...r.kernel.org
Cc:     Randy Dunlap <rdunlap@...radead.org>,
        Feng Zhou <zhoufeng.zf@...edance.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Chen Zhou <dingguo.cz@...group.com>
Subject: Re: [PATCH v17 03/10] x86: kdump: use macro CRASH_ADDR_LOW_MAX in
 functions reserve_crashkernel()

On 12/10/21 12:55 AM, Zhen Lei wrote:
> From: Chen Zhou <chenzhou10@...wei.com>
> 
> To make the functions reserve_crashkernel() as generic,
> replace some hard-coded numbers with macro CRASH_ADDR_LOW_MAX.
> 
> Signed-off-by: Chen Zhou <chenzhou10@...wei.com>
> Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
> Tested-by: John Donnelly <John.p.donnelly@...cle.com>
> Tested-by: Dave Kleikamp <dave.kleikamp@...cle.com>
> Acked-by: Baoquan He <bhe@...hat.com>

  Acked-by: John Donnelly <john.p.donnelly@...cle.com>

> ---
>   arch/x86/kernel/setup.c | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 6424ee4f23da2cf..bb2a0973b98059e 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -489,8 +489,9 @@ static void __init reserve_crashkernel(void)
>   	if (!crash_base) {
>   		/*
>   		 * Set CRASH_ADDR_LOW_MAX upper bound for crash memory,
> -		 * crashkernel=x,high reserves memory over 4G, also allocates
> -		 * 256M extra low memory for DMA buffers and swiotlb.
> +		 * crashkernel=x,high reserves memory over CRASH_ADDR_LOW_MAX,
> +		 * also allocates 256M extra low memory for DMA buffers
> +		 * and swiotlb.
>   		 * But the extra memory is not required for all machines.
>   		 * So try low memory first and fall back to high memory
>   		 * unless "crashkernel=size[KMG],high" is specified.
> @@ -518,7 +519,7 @@ static void __init reserve_crashkernel(void)
>   		}
>   	}
>   
> -	if (crash_base >= (1ULL << 32) && reserve_crashkernel_low()) {
> +	if (crash_base >= CRASH_ADDR_LOW_MAX && reserve_crashkernel_low()) {
>   		memblock_phys_free(crash_base, crash_size);
>   		return;
>   	}