• Russell King's avatar
    [ARM] mm 3: separate out supersection mappings, avoid for <4GB · 4a56c1e4
    Russell King authored
    Catalin Marinas at ARM Ltd says:
    > The CPU architects in ARM intended supersections only as a way to map
    > addresses >= 4GB. Supersections are not mandated by the architecture
    > and there is no easy way to detect their hardware support at run-time
    > (other than checking for a specific core). From the analysis done in
    > ARM, there wasn't a clear performance gain by using supersections
    > rather than sections (no significant improvement in the TLB misses).
    
    Therefore, we should avoid using supersections unless there's a real
    need (iow, we're mapping addresses >= 4GB).
    
    This means that we can simplify create_mapping() a bit since we will
    only use supersection mappings for addresses >= 4GB, which means that
    the physical, virtual and length must be multiples of the supersection
    mapping size.
    Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
    4a56c1e4
mmu.c 20 KB