[PATCH rebased 1/2] powerpc: reserve memory for capture kernel after hugepages init

[Michal Suchánek]

Hello,

This seems to cause crash with kdump reservation 1GB quite reliably.

Thanks

Michal

On Tue, Feb 18, 2020 at 05:28:34PM +0100, Michal Suchanek wrote:
> From: Hari Bathini <hbathini at linux.ibm.com>
> 
> Sometimes, memory reservation for KDump/FADump can overlap with memory
> marked for hugepages. This overlap leads to error, hang in KDump case
> and copy error reported by f/w in case of FADump, while trying to
> capture dump. Report error while setting up memory for the capture
> kernel instead of running into issues while capturing dump, by moving
> KDump/FADump reservation below MMU early init and failing gracefully
> when hugepages memory overlaps with capture kernel memory.
> 
> Signed-off-by: Hari Bathini <hbathini at linux.ibm.com>
> ---
>  arch/powerpc/kernel/prom.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
> index 6620f37abe73..0f14dc9c4dab 100644
> --- a/arch/powerpc/kernel/prom.c
> +++ b/arch/powerpc/kernel/prom.c
> @@ -735,14 +735,6 @@ void __init early_init_devtree(void *params)
>  	if (PHYSICAL_START > MEMORY_START)
>  		memblock_reserve(MEMORY_START, 0x8000);
>  	reserve_kdump_trampoline();
> -#if defined(CONFIG_FA_DUMP) || defined(CONFIG_PRESERVE_FA_DUMP)
> -	/*
> -	 * If we fail to reserve memory for firmware-assisted dump then
> -	 * fallback to kexec based kdump.
> -	 */
> -	if (fadump_reserve_mem() == 0)
> -#endif
> -		reserve_crashkernel();
>  	early_reserve_mem();
>  
>  	/* Ensure that total memory size is page-aligned. */
> @@ -781,6 +773,14 @@ void __init early_init_devtree(void *params)
>  #endif
>  
>  	mmu_early_init_devtree();
> +#if defined(CONFIG_FA_DUMP) || defined(CONFIG_PRESERVE_FA_DUMP)
> +	/*
> +	 * If we fail to reserve memory for firmware-assisted dump then
> +	 * fallback to kexec based kdump.
> +	 */
> +	if (fadump_reserve_mem() == 0)
> +#endif
> +		reserve_crashkernel();
>  
>  #ifdef CONFIG_PPC_POWERNV
>  	/* Scan and build the list of machine check recoverable ranges */
> -- 
> 2.23.0
>