[PATCH 1/4] powerpc/64s: Add DEBUG_PAGEALLOC for radix

[Michael Ellerman]

Nicholas Miehlbradt <nicholas at linux.ibm.com> writes:
> There is support for DEBUG_PAGEALLOC on hash but not on radix.
> Add support on radix.
>
> Signed-off-by: Nicholas Miehlbradt <nicholas at linux.ibm.com>
> ---
>  arch/powerpc/mm/book3s64/radix_pgtable.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c
> index db2f3d193448..483c99bfbde5 100644
> --- a/arch/powerpc/mm/book3s64/radix_pgtable.c
> +++ b/arch/powerpc/mm/book3s64/radix_pgtable.c
> @@ -30,6 +30,7 @@
>  #include <asm/trace.h>
>  #include <asm/uaccess.h>
>  #include <asm/ultravisor.h>
> +#include <asm/set_memory.h>
>  
>  #include <trace/events/thp.h>
>  
> @@ -503,6 +504,9 @@ static unsigned long __init radix_memory_block_size(void)
>  {
>  	unsigned long mem_block_size = MIN_MEMORY_BLOCK_SIZE;
>  
> +	if (debug_pagealloc_enabled())
> +		return PAGE_SIZE;
> +
>  	/*
>  	 * OPAL firmware feature is set by now. Hence we are ok
>  	 * to test OPAL feature.
> @@ -519,6 +523,9 @@ static unsigned long __init radix_memory_block_size(void)
>  
>  static unsigned long __init radix_memory_block_size(void)
>  {
> +	if (debug_pagealloc_enabled())
> +		return PAGE_SIZE;
> +
>  	return 1UL * 1024 * 1024 * 1024;
>  }
  
This value ends up in radix_mem_block_size, which is returned by 
pnv_memory_block_size(), which is wired up as ppc_md.memory_block_size,
and that's called by memory_block_size_bytes().

And I thought that value had to be >= MIN_MEMORY_BLOCK_SIZE.

#define MIN_MEMORY_BLOCK_SIZE     (1UL << SECTION_SIZE_BITS)
#define SECTION_SIZE_BITS       24


I would expect us to hit the panic in memory_dev_init().

So that's odd.

I suspect you need to leave radix_memory_block_size() alone, or at least
make sure you return MIN_MEMORY_BLOCK_SIZE when debug page alloc is
enabled.

We probably need a separate variable that holds the max page size used
for the linear mapping, and that would then be 1G in the normal case or
PAGE_SIZE in the debug page alloc case.

cheers