linux-kernel - Re: [PATCH] mips: kernel: setup: fix crash kernel resource allocation

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Date:   Sun, 7 Feb 2021 11:18:42 +0200
From:   Mike Rapoport <rppt@...nel.org>
To:     Ivan Khoronzhuk <ikhoronz@...co.com>
Cc:     linux-mips@...r.kernel.org, tsbogend@...ha.franken.de,
        linux-kernel@...r.kernel.org, yangtiezhu@...ngson.cn,
        ivan.khoronzhuk@...il.com
Subject: Re: [PATCH] mips: kernel: setup: fix crash kernel resource allocation

On Sat, Feb 06, 2021 at 12:59:40PM +0000, Ivan Khoronzhuk wrote:
> In order to avoid crash kernel corruption, its memory is reserved
> early in memblock and as result, in time when resources are inited
> it's not present in memblock.memory, so crash kernel memory is out
> of ranges listed with for_each_mem_range(). To avoid it and still
> keep memory reserved lets reseve it out of loop by inserting it in
> iomem_resource.

Unless I misread the code, the crash kernel memory is actually allocated
from memblock (memblock_find_in_range + memblock_reserve), but for some
reason memblock_reserve(<crash kernel>) is called outside
mips_parse_crashkernel(). So the crash kernel memory is surely in both
memblock.memory and memblock.reserved and it will be covered by
for_each_mem_range().

The mips_parse_crashkernel() function and the following reservation of
crash kernel memory should be merged, IMO, and this can be further
simplified with memblock_alloc() helpers.

Is there a particular issue you are trying to fix?
 
> Fixes: a94e4f24ec83 ("MIPS: init: Drop boot_mem_map")
> Signed-off-by: Ivan Khoronzhuk <ikhoronz@...co.com>
> ---
> Based on linux-next/master
> 
>  arch/mips/kernel/setup.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
> index 3785c72bc3bc..25e376ef2f2a 100644
> --- a/arch/mips/kernel/setup.c
> +++ b/arch/mips/kernel/setup.c
> @@ -473,14 +473,15 @@ static void __init mips_parse_crashkernel(void)
>  	crashk_res.end	 = crash_base + crash_size - 1;
>  }
>  
> -static void __init request_crashkernel(struct resource *res)
> +static void __init request_crashkernel(void)
>  {
>  	int ret;
>  
>  	if (crashk_res.start == crashk_res.end)
>  		return;
>  
> -	ret = request_resource(res, &crashk_res);
> +	/* The crashk resource shoud be located in normal mem */
> +	ret = insert_resource(&iomem_resource, &crashk_res);
>  	if (!ret)
>  		pr_info("Reserving %ldMB of memory at %ldMB for crashkernel\n",
>  			(unsigned long)(resource_size(&crashk_res) >> 20),
> @@ -734,8 +735,9 @@ static void __init resource_init(void)
>  		request_resource(res, &code_resource);
>  		request_resource(res, &data_resource);
>  		request_resource(res, &bss_resource);
> -		request_crashkernel(res);
>  	}
> +
> +	request_crashkernel();
>  }
>  
>  #ifdef CONFIG_SMP
> -- 
> 2.23.1
> 

-- 
Sincerely yours,
Mike.