[PATCH] ARM: kexec: fix crashkernel= handling

[Dave Young]

On 04/01/16 at 02:25pm, Russell King - ARM Linux wrote:

[snip]

> Well, if we want to remove it, we then need to sort out a method of
> specifying a limit on the address - where platforms physical memory
> bridges the 4GB CPU-accessible limit, the crashkernel region must be
> allocated below that so that it is boot-time accessible.
> 
> Some patches also have boot-time only aliases of RAM, with the normal
> alias above 4GB (eg, TI Keystone2) where the running view of RAM is
> at 0x800000000, but it has a non-coherent boot alias at 0x80000000.
> 
> I've patches which resolve some of the issues there, and making that
> change would make this patch dependent on those changes.  So, I
> recommend that this patch remains as-is for the time being, and this
> issue is addressed in a later patch after the Keystone2 idmap_to_phys()
> patches, similar to:
> 
> diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
> index 0a12fcf1aff6..74781e6d4e87 100644
> --- a/arch/arm/kernel/setup.c
> +++ b/arch/arm/kernel/setup.c
> @@ -962,7 +962,6 @@ late_initcall(init_machine_late);
>   * zImage relocating below the reserved region.
>   */
>  #define CRASH_ALIGN	(128 << 20)
> -#define CRASH_ADDR_MAX	(PHYS_OFFSET + (512 << 20))
>  
>  static inline unsigned long long get_total_mem(void)
>  {
> @@ -992,7 +991,8 @@ static void __init reserve_crashkernel(void)
>  		return;
>  
>  	if (crash_base <= 0) {
> -		crash_base = memblock_find_in_range(CRASH_ALIGN, CRASH_ADDR_MAX,
> +		unsigned long long crash_max = idmap_to_phys((u32)~0);
> +		crash_base = memblock_find_in_range(CRASH_ALIGN, crash_max,
>  						    crash_size, CRASH_ALIGN);
>  		if (!crash_base) {
>  			pr_err("crashkernel reservation failed - No suitable area found.\n");
> 
> Right now, I don't want to tie this facility to TI Keystone2 support
> as what this patch is doing is something that the ARM kexec support
> should have been doing since it was first introduced, so folk may
> want to backport this change to stable trees.

Is it possible for PHYS_OFFSET + (512 << 20) be larger than 4G assume that phys_addr_t is 32bit, if so it can be trunked to a small value then
the max will be wrong?

Otherwise I think use it temprarily is fine.

Thanks
Dave