powerpc/32s: Reorganise DSI handler.

The part decidated to handling hash_page() is fully unneeded for
processors not having real hash pages like the 603.

Lets enlarge the content of the feature fixup, and provide
an alternative which jumps directly instead of getting NIPs.

Also, in preparation of VMAP stacks, the end of DSI handler has moved
to later in the code as it won't fit anymore once VMAP stacks
are there.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/c31b22c91af8b011d0a4fd9e52ad6afb4b593f71.1576916812.git.christophe.leroy@c-s.fr

diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S
index 449625b..7ec7808 100644 (file)
--- a/arch/powerpc/kernel/head_32.S
+++ b/arch/powerpc/kernel/head_32.S
@@ -295,24 +295,20 @@ __secondary_hold_acknowledge:
        DO_KVM  0x300
 DataAccess:
        EXCEPTION_PROLOG
-       mfspr   r10,SPRN_DSISR
-       stw     r10,_DSISR(r11)
+       get_and_save_dar_dsisr_on_stack r4, r5, r11
+BEGIN_MMU_FTR_SECTION
 #ifdef CONFIG_PPC_KUAP
-       andis.  r0,r10,(DSISR_BAD_FAULT_32S | DSISR_DABRMATCH | DSISR_PROTFAULT)@h
+       andis.  r0, r5, (DSISR_BAD_FAULT_32S | DSISR_DABRMATCH | DSISR_PROTFAULT)@h
 #else
-       andis.  r0,r10,(DSISR_BAD_FAULT_32S|DSISR_DABRMATCH)@h
+       andis.  r0, r5, (DSISR_BAD_FAULT_32S | DSISR_DABRMATCH)@h
 #endif
-       bne     1f                      /* if not, try to put a PTE */
-       mfspr   r4,SPRN_DAR             /* into the hash table */
-       rlwinm  r3,r10,32-15,21,21      /* DSISR_STORE -> _PAGE_RW */
-BEGIN_MMU_FTR_SECTION
+       bne     handle_page_fault_tramp_2       /* if not, try to put a PTE */
+       rlwinm  r3, r5, 32 - 15, 21, 21         /* DSISR_STORE -> _PAGE_RW */
        bl      hash_page
-END_MMU_FTR_SECTION_IFSET(MMU_FTR_HPTE_TABLE)
-1:     lwz     r5,_DSISR(r11)          /* get DSISR value */
-       mfspr   r4,SPRN_DAR
-       stw     r4, _DAR(r11)
-       EXC_XFER_LITE(0x300, handle_page_fault)
-
+       b       handle_page_fault_tramp_1
+FTR_SECTION_ELSE
+       b       handle_page_fault_tramp_2
+ALT_MMU_FTR_SECTION_END_IFSET(MMU_FTR_HPTE_TABLE)
 
 /* Instruction access exception. */
        . = 0x400
@@ -642,6 +638,13 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_NEED_DTLB_SW_LRU)
 
        . = 0x3000
 
+handle_page_fault_tramp_1:
+       lwz     r4, _DAR(r11)
+       lwz     r5, _DSISR(r11)
+       /* fall through */
+handle_page_fault_tramp_2:
+       EXC_XFER_LITE(0x300, handle_page_fault)
+
 AltiVecUnavailable:
        EXCEPTION_PROLOG
 #ifdef CONFIG_ALTIVEC