On Fri, May 01, 2020 at 02:02:19AM -0700, Max Filippov wrote: > Hi Christoph, > > On Fri, May 1, 2020 at 1:46 AM Christoph Hellwig <h...@infradead.org> wrote: > > any idea why xtensa uses PAGE_KERNEL_EXEC instead of PAGE_KERNEL > > for kmap_prot? Mapping all mapped highmem as executable seems rather > > dangerous. > > I sure do: to allow instruction cache flushing when writing to high user > pages temporarily mapped with kmap. Instruction cache management > opcodes that operate on virtual addresses would raise an exception if > the address is not executable.
Seems like this should use kmap_atomic_prot with PAGE_KERNEL_EXEC just for that case. Which of course didn't exist on xtensa so far, but with this series will.
