powerpc/603: Avoid a pile of NOPs when not using SW LRU in TLB exceptions

The SW LRU is in an MMU feature section. When not used, that's a
dozen of NOPs to fetch for nothing.

Define an ALT section that does the few remaining operations.

That also avoids a double read on SRR1 in the SW LRU case.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/603725297466959419628ef7964aaf3417fb647d.1620363691.git.christophe.leroy@csgroup.eu

diff --git a/arch/powerpc/kernel/head_book3s_32.S b/arch/powerpc/kernel/head_book3s_32.S
index adf64fe..3262620 100644 (file)
--- a/arch/powerpc/kernel/head_book3s_32.S
+++ b/arch/powerpc/kernel/head_book3s_32.S
@@ -518,8 +518,6 @@ BEGIN_FTR_SECTION
        rlwinm  r1,r1,0,~_PAGE_COHERENT /* clear M (coherence not required) */
 END_FTR_SECTION_IFCLR(CPU_FTR_NEED_COHERENT)
        mtspr   SPRN_RPA,r1
-       mfspr   r2,SPRN_SRR1            /* Need to restore CR0 */
-       mtcrf   0x80,r2
 BEGIN_MMU_FTR_SECTION
        li      r0,1
        mfspr   r1,SPRN_SPRG_603_LRU
@@ -531,9 +529,15 @@ BEGIN_MMU_FTR_SECTION
        mfspr   r2,SPRN_SRR1
        rlwimi  r2,r0,31-14,14,14
        mtspr   SPRN_SRR1,r2
-END_MMU_FTR_SECTION_IFSET(MMU_FTR_NEED_DTLB_SW_LRU)
+       mtcrf   0x80,r2
+       tlbld   r3
+       rfi
+MMU_FTR_SECTION_ELSE
+       mfspr   r2,SPRN_SRR1            /* Need to restore CR0 */
+       mtcrf   0x80,r2
        tlbld   r3
        rfi
+ALT_MMU_FTR_SECTION_END_IFSET(MMU_FTR_NEED_DTLB_SW_LRU)
 DataAddressInvalid:
        mfspr   r3,SPRN_SRR1
        rlwinm  r1,r3,9,6,6     /* Get load/store bit */
@@ -607,9 +611,15 @@ BEGIN_MMU_FTR_SECTION
        mfspr   r2,SPRN_SRR1
        rlwimi  r2,r0,31-14,14,14
        mtspr   SPRN_SRR1,r2
-END_MMU_FTR_SECTION_IFSET(MMU_FTR_NEED_DTLB_SW_LRU)
+       mtcrf   0x80,r2
+       tlbld   r3
+       rfi
+MMU_FTR_SECTION_ELSE
+       mfspr   r2,SPRN_SRR1            /* Need to restore CR0 */
+       mtcrf   0x80,r2
        tlbld   r3
        rfi
+ALT_MMU_FTR_SECTION_END_IFSET(MMU_FTR_NEED_DTLB_SW_LRU)
 
 #ifndef CONFIG_ALTIVEC
 #define altivec_assist_exception       unknown_exception