linux-kernel - Re: [PATCH 1/2] arm64, kdump: enforce to take 4G as the crashkernel low memory end

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Date:   Mon, 5 Sep 2022 13:28:58 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     Baoquan He <bhe@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        catalin.marinas@....com, ardb@...nel.org,
        guanghuifeng@...ux.alibaba.com, mark.rutland@....com,
        will@...nel.org, linux-mm@...ck.org, thunder.leizhen@...wei.com,
        wangkefeng.wang@...wei.com, kexec@...ts.infradead.org
Subject: Re: [PATCH 1/2] arm64, kdump: enforce to take 4G as the crashkernel
 low memory end

On Thu, Sep 01, 2022 at 08:25:54PM +0800, Baoquan He wrote:
> On 09/01/22 at 10:24am, Mike Rapoport wrote:
> 
> max_zone_phys() only handles cases when CONFIG_ZONE_DMA/DMA32 enabled,
> the disabledCONFIG_ZONE_DMA/DMA32 case is not included. I can change
> it like:
> 
> static phys_addr_t __init crash_addr_low_max(void)
> {
>         phys_addr_t low_mem_mask = U32_MAX;
>         phys_addr_t phys_start = memblock_start_of_DRAM();
> 
>         if ((!IS_ENABLED(CONFIG_ZONE_DMA) && !IS_ENABLED(CONFIG_ZONE_DMA32)) ||
>              (phys_start > U32_MAX))
>                 low_mem_mask = PHYS_ADDR_MAX;
> 
>         return low_mem_mast + 1;
> }
> 
> or add the disabled CONFIG_ZONE_DMA/DMA32 case into crash_addr_low_max()
> as you suggested. Which one do you like better?
> 
> static phys_addr_t __init crash_addr_low_max(void)
> {
>         if (!IS_ENABLED(CONFIG_ZONE_DMA) && !IS_ENABLED(CONFIG_ZONE_DMA32))
> 		return PHYS_ADDR_MAX + 1;
> 
>         return max_zone_phys(32);
> }
 
I like the second variant better.

-- 
Sincerely yours,
Mike.