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    SubjectRe: [PATCH 2/9] arc: update comment about HIGHMEM implementation
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    On 02.06.21 12:53, Mike Rapoport wrote:
    > From: Mike Rapoport <rppt@linux.ibm.com>
    >
    > Arc does not use DISCONTIGMEM to implement high memory, update the comment
    > describing how high memory works to reflect this.
    >
    > Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
    > ---
    > arch/arc/mm/init.c | 13 +++++--------
    > 1 file changed, 5 insertions(+), 8 deletions(-)
    >
    > diff --git a/arch/arc/mm/init.c b/arch/arc/mm/init.c
    > index e2ed355438c9..397a201adfe3 100644
    > --- a/arch/arc/mm/init.c
    > +++ b/arch/arc/mm/init.c
    > @@ -139,16 +139,13 @@ void __init setup_arch_memory(void)
    >
    > #ifdef CONFIG_HIGHMEM
    > /*
    > - * Populate a new node with highmem
    > - *
    > * On ARC (w/o PAE) HIGHMEM addresses are actually smaller (0 based)
    > - * than addresses in normal ala low memory (0x8000_0000 based).
    > + * than addresses in normal aka low memory (0x8000_0000 based).
    > * Even with PAE, the huge peripheral space hole would waste a lot of
    > - * mem with single mem_map[]. This warrants a mem_map per region design.
    > - * Thus HIGHMEM on ARC is imlemented with DISCONTIGMEM.
    > - *
    > - * DISCONTIGMEM in turns requires multiple nodes. node 0 above is
    > - * populated with normal memory zone while node 1 only has highmem
    > + * mem with single contiguous mem_map[].
    > + * Thus when HIGHMEM on ARC is enabled the memory map corresponding
    > + * to the hole is freed and ARC specific version of pfn_valid()
    > + * handles the hole in the memory map.
    > */
    > #ifdef CONFIG_DISCONTIGMEM
    > node_set_online(1);
    >

    Reviewed-by: David Hildenbrand <david@redhat.com>

    --
    Thanks,

    David / dhildenb

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