Messages in this thread | | | From | Max Filippov <> | Date | Fri, 1 May 2020 02:50:27 -0700 | Subject | Re: xtensa question, was Re: [PATCH V1 00/10] Remove duplicated kmap code |
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On Fri, May 1, 2020 at 2:19 AM Christoph Hellwig <hch@infradead.org> wrote: > > 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 <hch@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.
Yeah, except it's the __access_remote_vm that does the kmap and then calls copy_to_user_page...
-- Thanks. -- Max
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