Re: [PATCH v2 17/20] mm: free_area_init: allow defining max_zone_pfn in descending order

[Mike Rapoport <rppt@xxxxxxxxxxxxx>]

On Tue, May 05, 2020 at 11:15:22PM +0300, Mike Rapoport wrote:
> On Tue, May 05, 2020 at 06:07:46PM +0000, Vineet Gupta wrote:
> > On 5/5/20 2:19 AM, Mike Rapoport wrote:
> 
> >  - Is it not better to have the core retain the flexibility just in case
> 
> If the requirement to have support for 3-banks is a theoretical
> possibility, I would prefer to adjust ARC's version of
> arch_has_descending_max_zone_pfns() to cope with either of 2-banks
> configuration (PAE40 and non-PAE40) and deal with the third bank when/if
> it actually materializes.
> 
> > Thx,
> > -Vineet
> 

The fix below should take care of any 2-bank configurations. 
This is vs. current mmotm.

>From eb8124fb3584607d1036b7ae00c8092ae43e480d Mon Sep 17 00:00:00 2001
From: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Date: Thu, 7 May 2020 23:44:15 +0300
Subject: [PATCH] arc: free_area_init(): take into account PAE40 mode

The arch_has_descending_max_zone_pfns() does not take into account physical
memory layout for PAE40 configuration.
With PAE40 enabled, the HIGHMEM is actually higher than NORMAL and
arch_has_descending_max_zone_pfns() should return false in this case.

Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
---
 arch/arc/mm/init.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arc/mm/init.c b/arch/arc/mm/init.c
index 386959bac3d2..e7bdc2ac1c87 100644
--- a/arch/arc/mm/init.c
+++ b/arch/arc/mm/init.c
@@ -79,7 +79,7 @@ void __init early_init_dt_add_memory_arch(u64 base, u64 size)
 
 bool arch_has_descending_max_zone_pfns(void)
 {
-	return true;
+	return !IS_ENABLED(CONFIG_ARC_HAS_PAE40);
 }
 
 /*
-- 
2.26.1


-- 
Sincerely yours,
Mike.