powerpc/64: Rearrange 64-bit _switch to prepare for 32/64 merge

More some 64-bit specifics out from the function epilogue and rearrange
this to be a bit neater, use 32-bit mem ops for CR save/restore, and
change some register numbers.

This is preparation to consolidate 32-bit and 64-bit switch code.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230606132447.315714-3-npiggin@gmail.com

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 2e02834..7430bd0 100644 (file)
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -190,12 +190,13 @@ _GLOBAL(_switch)
        mflr    r0
        std     r0,16(r1)
        stdu    r1,-SWITCH_FRAME_SIZE(r1)
+       std     r1,KSP(r3)      /* Set old stack pointer */
        /* r3-r13 are caller saved -- Cort */
        SAVE_NVGPRS(r1)
        std     r0,_NIP(r1)     /* Return to switch caller */
-       mfcr    r23
-       std     r23,_CCR(r1)
-       std     r1,KSP(r3)      /* Set old stack pointer */
+       mfcr    r0
+       stw     r0,_CCR(r1)
+       ld      r8,KSP(r4)      /* Load new stack pointer */
 
        kuap_check_amr r9, r10
 
@@ -232,14 +233,20 @@ _GLOBAL(_switch)
        DCBT_BOOK3S_STOP_ALL_STREAM_IDS(r6)
 #endif
 
-       addi    r6,r4,-THREAD   /* Convert THREAD to 'current' */
-       std     r6,PACACURRENT(r13)     /* Set new 'current' */
+       addi    r3,r3,-THREAD   /* old thread -> task_struct for return value */
+       addi    r6,r4,-THREAD   /* new thread -> task_struct */
+       std     r6,PACACURRENT(r13)     /* Set new task_struct to 'current' */
 #if defined(CONFIG_STACKPROTECTOR)
        ld      r6, TASK_CANARY(r6)
        std     r6, PACA_CANARY(r13)
 #endif
-
-       ld      r8,KSP(r4)      /* new stack pointer */
+       /* Set the new PACAKSAVE */
+       clrrdi  r7, r8, THREAD_SHIFT    /* base of new stack */
+       /* Note: this uses SWITCH_FRAME_SIZE rather than INT_FRAME_SIZE
+          because we don't need to leave the 288-byte ABI gap at the
+          top of the kernel stack. */
+       addi    r7,r7,THREAD_SIZE-SWITCH_FRAME_SIZE
+       std     r7,PACAKSAVE(r13)
 
 #ifdef CONFIG_PPC_64S_HASH_MMU
 BEGIN_MMU_FTR_SECTION
@@ -247,12 +254,6 @@ BEGIN_MMU_FTR_SECTION
 END_MMU_FTR_SECTION_IFCLR(MMU_FTR_TYPE_RADIX)
 #endif
 
-       clrrdi  r7, r8, THREAD_SHIFT    /* base of new stack */
-       /* Note: this uses SWITCH_FRAME_SIZE rather than INT_FRAME_SIZE
-          because we don't need to leave the 288-byte ABI gap at the
-          top of the kernel stack. */
-       addi    r7,r7,THREAD_SIZE-SWITCH_FRAME_SIZE
-
        /*
         * PMU interrupts in radix may come in here. They will use r1, not
         * PACAKSAVE, so this stack switch will not cause a problem. They
@@ -262,18 +263,15 @@ END_MMU_FTR_SECTION_IFCLR(MMU_FTR_TYPE_RADIX)
         * active on the new CPU, will order those stores.
         */
        mr      r1,r8           /* start using new stack pointer */
-       std     r7,PACAKSAVE(r13)
 
-       ld      r6,_CCR(r1)
-       mtcrf   0xFF,r6
+       lwz     r0,_CCR(r1)
+       mtcrf   0xFF,r0
 
        /* r3-r13 are destroyed -- Cort */
        REST_NVGPRS(r1)
 
-       /* convert old thread to its task_struct for return value */
-       addi    r3,r3,-THREAD
-       ld      r7,_NIP(r1)     /* Return to _switch caller in new task */
-       mtlr    r7
+       ld      r0,_NIP(r1)     /* Return to _switch caller in new task */
+       mtlr    r0
        addi    r1,r1,SWITCH_FRAME_SIZE
        blr