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powerpc/32s: Use SPRN_SPRG_SCRATCH2 in DSI prolog 

Use SPRN_SPRG_SCRATCH2 as an alternative scratch register in
the early part of DSI prolog in order to avoid clobbering
SPRN_SPRG_SCRATCH0/1 used by other prologs.

The 603 doesn't like a jump from DataLoadTLBMiss to the 10 nops
that are now in the beginning of DSI exception as a result of
the feature section. To workaround this, add a jump as alternative.
It also avoids fetching 10 nops for nothing.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/f9f8df2a2be93568768ef1ac793639f7914cf103.1606285014.git.christophe.leroy@csgroup.eu
This commit is contained in:
Christophe Leroy 2020-11-25 07:10:52 +00:00 committed by Michael Ellerman
parent 6285f9cff5
commit de1cd07906
2 changed files with 9 additions and 16 deletions
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1
arch/powerpc/include/asm/reg.h
View File

@ -1204,6 +1204,7 @@
#ifdef CONFIG_PPC_BOOK3S_32
#define SPRN_SPRG_SCRATCH0 SPRN_SPRG0
#define SPRN_SPRG_SCRATCH1 SPRN_SPRG1
#define SPRN_SPRG_SCRATCH2 SPRN_SPRG2
#define SPRN_SPRG_603_LRU SPRN_SPRG4
#endif

24
arch/powerpc/kernel/head_book3s_32.S
View File

@ -288,9 +288,9 @@ MachineCheck:
DO_KVM 0x300
DataAccess:
#ifdef CONFIG_VMAP_STACK
mtspr SPRN_SPRG_SCRATCH0,r10
mfspr r10, SPRN_SPRG_THREAD
BEGIN_MMU_FTR_SECTION
mtspr SPRN_SPRG_SCRATCH2,r10
mfspr r10, SPRN_SPRG_THREAD
stw r11, THR11(r10)
mfspr r10, SPRN_DSISR
mfcr r11
@ -304,19 +304,11 @@ BEGIN_MMU_FTR_SECTION
.Lhash_page_dsi_cont:
mtcr r11
lwz r11, THR11(r10)
END_MMU_FTR_SECTION_IFSET(MMU_FTR_HPTE_TABLE)
mtspr SPRN_SPRG_SCRATCH1,r11
mfspr r11, SPRN_DAR
stw r11, DAR(r10)
mfspr r11, SPRN_DSISR
stw r11, DSISR(r10)
mfspr r11, SPRN_SRR0
stw r11, SRR0(r10)
mfspr r11, SPRN_SRR1 /* check whether user or kernel */
stw r11, SRR1(r10)
mfcr r10
andi. r11, r11, MSR_PR
mfspr r10, SPRN_SPRG_SCRATCH2
MMU_FTR_SECTION_ELSE
b 1f
ALT_MMU_FTR_SECTION_END_IFSET(MMU_FTR_HPTE_TABLE)
1: EXCEPTION_PROLOG_0 handle_dar_dsisr=1
EXCEPTION_PROLOG_1
b handle_page_fault_tramp_1
#else /* CONFIG_VMAP_STACK */
@ -764,7 +756,7 @@ fast_hash_page_return:
/* DSI */
mtcr r11
lwz r11, THR11(r10)
mfspr r10, SPRN_SPRG_SCRATCH0
mfspr r10, SPRN_SPRG_SCRATCH2
rfi
1: /* ISI */