powerpc/64s/exception: simplify hmi control flow

Branch to the relocated 0xc000 address early (still in real mode), to
simplify subsequent branches. Have the virt mode handler avoid just
'windup' and redo the exception from scratch, rather than branching
back to the trampoline.

Rearrange the stack setup instruction location to match the system
reset handler (e.g., right before EXCEPTION_PROLOG_COMMON).

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index c6e1d1a..eee5bef 100644 (file)
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -260,17 +260,6 @@ END_FTR_SECTION_NESTED(ftr,ftr,943)
        mtctr   reg;                                                    \
        bctr
 
-#ifdef CONFIG_RELOCATABLE
-#define BRANCH_LINK_TO_FAR(label)                                      \
-       __LOAD_FAR_HANDLER(r12, label);                                 \
-       mtctr   r12;                                                    \
-       bctrl
-
-#else
-#define BRANCH_LINK_TO_FAR(label)                                      \
-       bl      label
-#endif
-
 #ifdef CONFIG_KVM_BOOK3S_64_HANDLER
 #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
 /*
@@ -1713,22 +1702,26 @@ EXC_REAL_BEGIN(hmi_exception, 0xe60, 0x20)
        EXCEPTION_PROLOG_0 PACA_EXGEN
        b       hmi_exception_early
 EXC_REAL_END(hmi_exception, 0xe60, 0x20)
-__TRAMP_REAL_OOL_MASKABLE_HV(hmi_exception, 0xe60, IRQS_DISABLED)
 EXC_VIRT_NONE(0x4e60, 0x20)
 TRAMP_KVM_HV(PACA_EXGEN, 0xe60)
 TRAMP_REAL_BEGIN(hmi_exception_early)
        EXCEPTION_PROLOG_1 EXC_HV, PACA_EXGEN, 1, 0xe60, 0, 0, 0
+       mfctr   r10                     /* save ctr, even for !RELOCATABLE */
+       BRANCH_TO_C000(r11, hmi_exception_early_common)
+
+EXC_COMMON_BEGIN(hmi_exception_early_common)
+       mtctr   r10                     /* Restore ctr */
+       mfspr   r11,SPRN_HSRR0          /* Save HSRR0 */
+       mfspr   r12,SPRN_HSRR1          /* Save HSRR1 */
        mr      r10,r1                  /* Save r1 */
        ld      r1,PACAEMERGSP(r13)     /* Use emergency stack for realmode */
        subi    r1,r1,INT_FRAME_SIZE    /* alloc stack frame            */
-       mfspr   r11,SPRN_HSRR0          /* Save HSRR0 */
-       mfspr   r12,SPRN_HSRR1          /* Save HSRR1 */
        EXCEPTION_PROLOG_COMMON_1()
        /* We don't touch AMR here, we never go to virtual mode */
        EXCEPTION_PROLOG_COMMON_2(PACA_EXGEN)
        EXCEPTION_PROLOG_COMMON_3(0xe60)
        addi    r3,r1,STACK_FRAME_OVERHEAD
-       BRANCH_LINK_TO_FAR(DOTSYM(hmi_exception_realmode)) /* Function call ABI */
+       bl      hmi_exception_realmode
        cmpdi   cr0,r3,0
        bne     1f
 
@@ -1742,7 +1735,8 @@ TRAMP_REAL_BEGIN(hmi_exception_early)
         */
        EXCEPTION_RESTORE_REGS EXC_HV
        EXCEPTION_PROLOG_0 PACA_EXGEN
-       b       tramp_real_hmi_exception
+       EXCEPTION_PROLOG_1 EXC_HV, PACA_EXGEN, 1, 0xe60, 0, 0, IRQS_DISABLED
+       EXCEPTION_PROLOG_2_REAL hmi_exception_common, EXC_HV, 1
 
 EXC_COMMON_BEGIN(hmi_exception_common)
        EXCEPTION_COMMON(PACA_EXGEN, 0xe60)