From: leroy christophe

Le 06/01/2015 13:08, David Laight a =E9crit :

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On Tue, 2014-12-16 at 16:03 +0100, Christophe Leroy wrote:

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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 re=

move the

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ori instruction.

Signed-off-by: Christophe Leroy <redacted>

Nice :)
Acked-by: Joakim Tjernlund <redacted>

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---
  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/hea=

d_8xx.S

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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

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-       lwz     r11, 0(r11)/* Get the level 1 entry */
+       lwz     r11, (swapper_pg_dir-PAGE_OFFSET)@l(r11)/* Get the le=

vel 1 entry */

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On the face of it that fragment doesn't look right when CONFIG_MODULES =

is undefined.

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	David

I'm not sure I understand what you mean.
=20
The other part of the patch adds the following:
+    li    r5, (swapper_pg_dir-PAGE_OFFSET)@l
+    sub    r4, r4, r5
=20
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