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Commit 910a8643 authored by John David Anglin's avatar John David Anglin Committed by Helge Deller
Browse files

parisc: Update comment regarding implementation of copy_user_page_asm 



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: default avatarJohn David Anglin <dave.anglin@bell.net>
Signed-off-by: default avatarHelge Deller <deller@gmx.de>
parent c4351d98

arch/parisc/kernel/pacache.S

+11 −5
Original line number Original line Diff line number Diff line
@@ -573,11 +573,17 @@ ENDPROC(copy_page_asm) 
	.endm

	.endm





	/*

	/*

	 * We can't do this since copy_user_page is used to bring in

	 * copy_user_page_asm() performs a page copy using mappings

	 * file data that might have instructions. Since the data would

	 * equivalent to the user page mappings.  It can be used to

	 * then need to be flushed out so the i-fetch can see it, it

	 * implement copy_user_page() but unfortunately both the `from'

	 * makes more sense to just copy through the kernel translation

	 * and `to' pages need to be flushed through mappings equivalent

	 * and flush it.

	 * 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

	 * I'm still keeping this around because it may be possible to

	 * use it if more information is passed into copy_user_page().

	 * use it if more information is passed into copy_user_page().