Commit 276d5aff authored by Christophe Leroy's avatar Christophe Leroy Committed by Andrew Morton
Browse files

powerpc/e500: don't pre-check write access on data TLB error 

Don't pre-check write access on read-only pages on data TLB error.

Load the TLB anyway and take a DSI exception when it happens.  This avoids
reading SPRN_ESR at every data TLB error exception.

Link: https://lkml.kernel.org/r/8525518e1657d6032b7e980c1888102828d66950.1719928057.git.christophe.leroy@csgroup.eu


Signed-off-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 84319905

arch/powerpc/kernel/head_85xx.S

+0 −15
Original line number Diff line number Diff line
@@ -472,27 +472,12 @@ END_BTB_FLUSH_SECTION 
#endif



4:

	/* Mask of required permission bits. Note that while we

	 * do copy ESR:ST to _PAGE_WRITE position as trying to write

	 * to an RO page is pretty common, we don't do it with

	 * _PAGE_DIRTY. We could do it, but it's a fairly rare

	 * event so I'd rather take the overhead when it happens

	 * rather than adding an instruction here. We should measure

	 * whether the whole thing is worth it in the first place

	 * as we could avoid loading SPRN_ESR completely in the first

	 * place...

	 *

	 * TODO: Is it worth doing that mfspr & rlwimi in the first

	 *       place or can we save a couple of instructions here ?

	 */

	mfspr	r12,SPRN_ESR

#ifdef CONFIG_PTE_64BIT

	li	r13,_PAGE_PRESENT|_PAGE_BAP_SR

	oris	r13,r13,_PAGE_ACCESSED@h

#else

	li	r13,_PAGE_PRESENT|_PAGE_READ|_PAGE_ACCESSED

#endif

	rlwimi	r13,r12,11,29,29



	FIND_PTE

	andc.	r13,r13,r11		/* Check permission */