From: leroy christophe
> Le 06/01/2015 13:08, David Laight a écrit :
> >> On Tue, 2014-12-16 at 16:03 +0100, Christophe Leroy wrote:
> >>> All accessed to PGD entries are done via 0(r11).
> >>> By using lower part of swapper_pg_dir as load index to r11, we can remove
> >>> the
> >>> ori instruction.
> >>>
> >>> Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr>
> >> Nice :)
> >> Acked-by: Joakim Tjernlund <joakim.tjernl...@transmode.se>
> >>
> >>> ---
> >>> arch/powerpc/kernel/head_8xx.S | 22 ++++++++++------------
> >>> 1 file changed, 10 insertions(+), 12 deletions(-)
> >>>
> >>> diff --git a/arch/powerpc/kernel/head_8xx.S
> >>> b/arch/powerpc/kernel/head_8xx.S
> >>> index ae05f28..aa45225 100644
> >>> --- a/arch/powerpc/kernel/head_8xx.S
> >>> +++ b/arch/powerpc/kernel/head_8xx.S
> >>> @@ -322,13 +322,12 @@ InstructionTLBMiss:
> >>> mfspr r11, SPRN_M_TW/* Get level 1 table base address */
> >>> #ifdef CONFIG_MODULES
> >>> beq 3f
> >>> - lis r11, (swapper_pg_dir-PAGE_OFFSET)@h
> >>> - ori r11, r11, (swapper_pg_dir-PAGE_OFFSET)@l
> >>> + lis r11, (swapper_pg_dir-PAGE_OFFSET)@ha
> >>> 3:
> >>> #endif
> >>> /* Insert level 1 index */
> >>> rlwimi r11, r10, 32 - ((PAGE_SHIFT - 2) << 1), (PAGE_SHIFT - 2)
> >>> << 1, 29
> >>> - lwz r11, 0(r11)/* Get the level 1 entry */
> >>> + lwz r11, (swapper_pg_dir-PAGE_OFFSET)@l(r11)/* Get the level
> >>> 1 entry */
> >>>
> > On the face of it that fragment doesn't look right when CONFIG_MODULES is
> > undefined.
> >
> > David
> >
> I'm not sure I understand what you mean.
>
> The other part of the patch adds the following:
> + li r5, (swapper_pg_dir-PAGE_OFFSET)@l
> + sub r4, r4, r5
>
> r4 is the value put into SPRN_M_TW, so I don't see what may be wrong.
Ok, but it is completely non-obvious.
You probably need to change some comments somewhere about what is held
in SPRN_M_TW - since it is no longer the L1 base address, but that value
offset by some 'random' amount.
David
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