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support to clear contiguous extents in a single >> operation (ex. via FEAT_MOPS on arm64, string instructions on x86) >> which excludes any possibility of interspersing kmap()/kunmap(). > > I'm feeling dumb. What does the use of a string instruction have to do > with kmap/kunmap? Sorry, that might have been unnecessarily inscrutable. How about something like this: This is only enabled with !CONFIG_HIGHMEM because the intent is to use architecture support to clear contiguous extents in a single interruptible operation (ex. via FEAT_MOPS on arm64, string instructions on x86). Given that we might be zeroing the whole extent with a single instruction, this excludes any possibility of constructing intermediate HIGHMEM maps. -- ankur