Re: [PATCH 2/2] powerpc: avoid adjusting memory_limit for capture kernel memory reservation

["Michal Suchánek" <msuchanek@suse.de>]

On Fri, 28 Jun 2019 00:51:19 +0530
Hari Bathini <hbathini@linux.ibm.com> wrote:

> Currently, if memory_limit is specified and it overlaps with memory to
> be reserved for capture kernel, memory_limit is adjusted to accommodate
> capture kernel. With memory reservation for capture kernel moved later
> (after enforcing memory limit), this adjustment no longer holds water.
> So, avoid adjusting memory_limit and error out instead.

Can you split out the memory limit adjustment out of memory reservation
so it can still be adjusted?

Thanks

Michal
> 
> Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
> ---
>  arch/powerpc/kernel/fadump.c        |   16 ----------------
>  arch/powerpc/kernel/machine_kexec.c |   22 +++++++++++-----------
>  2 files changed, 11 insertions(+), 27 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
> index 4eab972..a784695 100644
> --- a/arch/powerpc/kernel/fadump.c
> +++ b/arch/powerpc/kernel/fadump.c
> @@ -476,22 +476,6 @@ int __init fadump_reserve_mem(void)
>  #endif
>  	}
>  
> -	/*
> -	 * Calculate the memory boundary.
> -	 * If memory_limit is less than actual memory boundary then reserve
> -	 * the memory for fadump beyond the memory_limit and adjust the
> -	 * memory_limit accordingly, so that the running kernel can run with
> -	 * specified memory_limit.
> -	 */
> -	if (memory_limit && memory_limit < memblock_end_of_DRAM()) {
> -		size = get_fadump_area_size();
> -		if ((memory_limit + size) < memblock_end_of_DRAM())
> -			memory_limit += size;
> -		else
> -			memory_limit = memblock_end_of_DRAM();
> -		printk(KERN_INFO "Adjusted memory_limit for firmware-assisted"
> -				" dump, now %#016llx\n", memory_limit);
> -	}
>  	if (memory_limit)
>  		memory_boundary = memory_limit;
>  	else
> diff --git a/arch/powerpc/kernel/machine_kexec.c b/arch/powerpc/kernel/machine_kexec.c
> index c4ed328..fc5533b 100644
> --- a/arch/powerpc/kernel/machine_kexec.c
> +++ b/arch/powerpc/kernel/machine_kexec.c
> @@ -125,10 +125,8 @@ void __init reserve_crashkernel(void)
>  		crashk_res.end = crash_base + crash_size - 1;
>  	}
>  
> -	if (crashk_res.end == crashk_res.start) {
> -		crashk_res.start = crashk_res.end = 0;
> -		return;
> -	}
> +	if (crashk_res.end == crashk_res.start)
> +		goto error_out;
>  
>  	/* We might have got these values via the command line or the
>  	 * device tree, either way sanitise them now. */
> @@ -170,15 +168,13 @@ void __init reserve_crashkernel(void)
>  	if (overlaps_crashkernel(__pa(_stext), _end - _stext)) {
>  		printk(KERN_WARNING
>  			"Crash kernel can not overlap current kernel\n");
> -		crashk_res.start = crashk_res.end = 0;
> -		return;
> +		goto error_out;
>  	}
>  
>  	/* Crash kernel trumps memory limit */
>  	if (memory_limit && memory_limit <= crashk_res.end) {
> -		memory_limit = crashk_res.end + 1;
> -		printk("Adjusted memory limit for crashkernel, now 0x%llx\n",
> -		       memory_limit);
> +		pr_err("Crash kernel size can't exceed memory_limit\n");
> +		goto error_out;
>  	}
>  
>  	printk(KERN_INFO "Reserving %ldMB of memory at %ldMB "
> @@ -190,9 +186,13 @@ void __init reserve_crashkernel(void)
>  	if (!memblock_is_region_memory(crashk_res.start, crash_size) ||
>  	    memblock_reserve(crashk_res.start, crash_size)) {
>  		pr_err("Failed to reserve memory for crashkernel!\n");
> -		crashk_res.start = crashk_res.end = 0;
> -		return;
> +		goto error_out;
>  	}
> +
> +	return;
> +error_out:
> +	crashk_res.start = crashk_res.end = 0;
> +	return;
>  }
>  
>  int overlaps_crashkernel(unsigned long start, unsigned long size)
>