| Message ID | 20210426101004.42695-1-isaev@synopsys.com |
|---|---|
| State | New |
| Headers | show |
| Series | ARC: Use max_high_pfn as a HIGHMEM zone border | expand |
Hi, On Mon, Apr 26, 2021 at 01:10:04PM +0300, Vladimir Isaev wrote: > Commit 4af22ded0ecf ("arc: fix memory initialization for systems with two > memory banks") fixed highmem, but not for PAE case when highmem is > actually bigger than lowmem. > > Signed-off-by: Vladimir Isaev <isaev@synopsys.com> > Cc: Mike Rapoport <rppt@linux.ibm.com> > --- > 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 ce07e697916c..59bad6f94105 100644 > --- a/arch/arc/mm/init.c > +++ b/arch/arc/mm/init.c > @@ -157,7 +157,7 @@ void __init setup_arch_memory(void) > min_high_pfn = PFN_DOWN(high_mem_start); > max_high_pfn = PFN_DOWN(high_mem_start + high_mem_sz); > > - max_zone_pfn[ZONE_HIGHMEM] = min_low_pfn; > + max_zone_pfn[ZONE_HIGHMEM] = max_high_pfn; This is correct with PAE40, but it will break !PAE40 when "highmem" has lower addresses than lowmem. It rather should be something like: if (IS_ENABLED(CONFIG_ARC_HAS_PAE40)) max_zone_pfn[ZONE_HIGHMEM] = max_high_pfn; else max_zone_pfn[ZONE_HIGHMEM] = min_low_pfn; > > high_memory = (void *)(min_high_pfn << PAGE_SHIFT); > > -- > 2.16.2 >
Hi Mike, On Mon, April 26, 2021 2:29 PM, Mike Rapoport wrote: > On Mon, Apr 26, 2021 at 01:10:04PM +0300, Vladimir Isaev wrote: > > - max_zone_pfn[ZONE_HIGHMEM] = min_low_pfn; > > + max_zone_pfn[ZONE_HIGHMEM] = max_high_pfn; > > This is correct with PAE40, but it will break !PAE40 when "highmem" has lower > addresses than lowmem. > > It rather should be something like: > > if (IS_ENABLED(CONFIG_ARC_HAS_PAE40)) > max_zone_pfn[ZONE_HIGHMEM] = max_high_pfn; > else > max_zone_pfn[ZONE_HIGHMEM] = min_low_pfn; > Not sure if I understand why we should have min_low_pfn here. In !PAE40 case max_high_pfn just will be smaller than min_low_pfn. Thank you, Vladimir Isaev
On Mon, Apr 26, 2021 at 11:55:00AM +0000, Vladimir Isaev wrote: > Hi Mike, > > On Mon, April 26, 2021 2:29 PM, Mike Rapoport wrote: > > On Mon, Apr 26, 2021 at 01:10:04PM +0300, Vladimir Isaev wrote: > > > - max_zone_pfn[ZONE_HIGHMEM] = min_low_pfn; > > > + max_zone_pfn[ZONE_HIGHMEM] = max_high_pfn; > > > > This is correct with PAE40, but it will break !PAE40 when "highmem" has lower > > addresses than lowmem. > > > > It rather should be something like: > > > > if (IS_ENABLED(CONFIG_ARC_HAS_PAE40)) > > max_zone_pfn[ZONE_HIGHMEM] = max_high_pfn; > > else > > max_zone_pfn[ZONE_HIGHMEM] = min_low_pfn; > > > > Not sure if I understand why we should have min_low_pfn here. In !PAE40 > case max_high_pfn just will be smaller than min_low_pfn. Hmm, actually, you are right. This should be fine.
On 4/26/21 9:15 AM, Mike Rapoport wrote: > On Mon, Apr 26, 2021 at 11:55:00AM +0000, Vladimir Isaev wrote: >> Hi Mike, >> >> On Mon, April 26, 2021 2:29 PM, Mike Rapoport wrote: >>> On Mon, Apr 26, 2021 at 01:10:04PM +0300, Vladimir Isaev wrote: >>>> - max_zone_pfn[ZONE_HIGHMEM] = min_low_pfn; >>>> + max_zone_pfn[ZONE_HIGHMEM] = max_high_pfn; >>> This is correct with PAE40, but it will break !PAE40 when "highmem" has lower >>> addresses than lowmem. >>> >>> It rather should be something like: >>> >>> if (IS_ENABLED(CONFIG_ARC_HAS_PAE40)) >>> max_zone_pfn[ZONE_HIGHMEM] = max_high_pfn; >>> else >>> max_zone_pfn[ZONE_HIGHMEM] = min_low_pfn; >>> >> Not sure if I understand why we should have min_low_pfn here. In !PAE40 >> case max_high_pfn just will be smaller than min_low_pfn. > Hmm, actually, you are right. This should be fine. But still worth adding a comment. If this could trip the person who did the massive cross-arch rework then I don't know what mere mortals would run into ;-) -Vineet
diff --git a/arch/arc/mm/init.c b/arch/arc/mm/init.c index ce07e697916c..59bad6f94105 100644 --- a/arch/arc/mm/init.c +++ b/arch/arc/mm/init.c @@ -157,7 +157,7 @@ void __init setup_arch_memory(void) min_high_pfn = PFN_DOWN(high_mem_start); max_high_pfn = PFN_DOWN(high_mem_start + high_mem_sz); - max_zone_pfn[ZONE_HIGHMEM] = min_low_pfn; + max_zone_pfn[ZONE_HIGHMEM] = max_high_pfn; high_memory = (void *)(min_high_pfn << PAGE_SHIFT);
Commit 4af22ded0ecf ("arc: fix memory initialization for systems with two memory banks") fixed highmem, but not for PAE case when highmem is actually bigger than lowmem. Signed-off-by: Vladimir Isaev <isaev@synopsys.com> Cc: Mike Rapoport <rppt@linux.ibm.com> --- arch/arc/mm/init.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)