The attached patch describes the current implementation of copy_user_page_asm. It is possible to implement this routine using either the kernel page mappings or equivalent aliases. I tested both and decided the former was more efficient. Signed-off-by: John David Anglin <dave.anglin@xxxxxxxx>
diff --git a/arch/parisc/kernel/pacache.S b/arch/parisc/kernel/pacache.S index b743a80..1250c02 100644 --- a/arch/parisc/kernel/pacache.S +++ b/arch/parisc/kernel/pacache.S @@ -573,11 +573,17 @@ ENDPROC(copy_page_asm) .endm /* - * We can't do this since copy_user_page is used to bring in - * file data that might have instructions. Since the data would - * then need to be flushed out so the i-fetch can see it, it - * makes more sense to just copy through the kernel translation - * and flush it. + * copy_user_page_asm() performs a page copy using mappings + * equivalent to the user page mappings. It can be used to + * implement copy_user_page() but unfortunately both the `from' + * and `to' pages need to be flushed through mappings equivalent + * to the user mappings after the copy because the kernel accesses + * the `from' page through the kmap kernel mapping and the `to' + * page needs to be flushed since code can be copied. As a + * result, this implementation is less efficient than the simpler + * copy using the kernel mapping. It only needs the `from' page + * to flushed via the user mapping. The kunmap routines handle + * the flushes needed for the kernel mapping. * * I'm still keeping this around because it may be possible to * use it if more information is passed into copy_user_page().
-- John David Anglin dave.anglin@xxxxxxxx
