From 0df977eafc792a5365a7f81d8d5920132e03afad Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Thu, 21 Feb 2019 10:37:54 +0000 Subject: [PATCH] powerpc/6xx: Don't use SPRN_SPRG2 for storing stack pointer while in RTAS When calling RTAS, the stack pointer is stored in SPRN_SPRG2 in order to be able to restore it in case of machine check in RTAS. As machine check is not a perfomance critical path, this patch frees SPRN_SPRG2 by using a field in thread struct instead. Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman --- arch/powerpc/include/asm/processor.h | 3 +++ arch/powerpc/include/asm/reg.h | 1 - arch/powerpc/kernel/asm-offsets.c | 3 +++ arch/powerpc/kernel/entry_32.S | 5 +++-- arch/powerpc/kernel/head_32.S | 22 ++++++++++++---------- 5 files changed, 21 insertions(+), 13 deletions(-) diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h index ee58526cb6c2..e8682122ea3d 100644 --- a/arch/powerpc/include/asm/processor.h +++ b/arch/powerpc/include/asm/processor.h @@ -250,6 +250,9 @@ struct thread_struct { #ifdef CONFIG_PPC32 void *pgdir; /* root of page-table tree */ unsigned long ksp_limit; /* if ksp <= ksp_limit stack overflow */ +#ifdef CONFIG_PPC_RTAS + unsigned long rtas_sp; /* stack pointer for when in RTAS */ +#endif #endif /* Debug Registers */ struct debug_reg debug; diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h index 1c98ef1f2d5b..371ef6e8248e 100644 --- a/arch/powerpc/include/asm/reg.h +++ b/arch/powerpc/include/asm/reg.h @@ -1167,7 +1167,6 @@ #ifdef CONFIG_PPC_BOOK3S_32 #define SPRN_SPRG_SCRATCH0 SPRN_SPRG0 #define SPRN_SPRG_SCRATCH1 SPRN_SPRG1 -#define SPRN_SPRG_RTAS SPRN_SPRG2 #define SPRN_SPRG_603_LRU SPRN_SPRG4 #endif diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c index 9ffc72ded73a..d6f9bdb1eb2e 100644 --- a/arch/powerpc/kernel/asm-offsets.c +++ b/arch/powerpc/kernel/asm-offsets.c @@ -93,6 +93,9 @@ int main(void) OFFSET(THREAD_INFO, task_struct, stack); DEFINE(THREAD_INFO_GAP, _ALIGN_UP(sizeof(struct thread_info), 16)); OFFSET(KSP_LIMIT, thread_struct, ksp_limit); +#ifdef CONFIG_PPC_RTAS + OFFSET(RTAS_SP, thread_struct, rtas_sp); +#endif #endif /* CONFIG_PPC64 */ #ifdef CONFIG_LIVEPATCH diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S index c2b66fbbf7f0..6c671ceb5a06 100644 --- a/arch/powerpc/kernel/entry_32.S +++ b/arch/powerpc/kernel/entry_32.S @@ -1332,7 +1332,7 @@ _GLOBAL(enter_rtas) MTMSRD(r0) /* don't get trashed */ li r9,MSR_KERNEL & ~(MSR_IR|MSR_DR) mtlr r6 - mtspr SPRN_SPRG_RTAS,r7 + stw r7, THREAD + RTAS_SP(r2) mtspr SPRN_SRR0,r8 mtspr SPRN_SRR1,r9 RFI @@ -1341,7 +1341,8 @@ _GLOBAL(enter_rtas) lwz r9,8(r9) /* original msr value */ addi r1,r1,INT_FRAME_SIZE li r0,0 - mtspr SPRN_SPRG_RTAS,r0 + tophys(r7, r2) + stw r0, THREAD + RTAS_SP(r7) mtspr SPRN_SRR0,r8 mtspr SPRN_SRR1,r9 RFI /* return to caller */ diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S index c2f564690778..04128899a0a5 100644 --- a/arch/powerpc/kernel/head_32.S +++ b/arch/powerpc/kernel/head_32.S @@ -352,9 +352,8 @@ i##n: \ * registers that might have bad values includes all the GPRs * and all the BATs. We indicate that we are in RTAS by putting * a non-zero value, the address of the exception frame to use, - * in SPRG2. The machine check handler checks SPRG2 and uses its - * value if it is non-zero. If we ever needed to free up SPRG2, - * we could use a field in the thread_info or thread_struct instead. + * in thread.rtas_sp. The machine check handler checks thread.rtas_sp + * and uses its value if it is non-zero. * (Other exception handlers assume that r1 is a valid kernel stack * pointer when we take an exception from supervisor mode.) * -- paulus. @@ -365,16 +364,15 @@ i##n: \ mtspr SPRN_SPRG_SCRATCH1,r11 mfcr r10 #ifdef CONFIG_PPC_CHRP - mfspr r11,SPRN_SPRG_RTAS - cmpwi 0,r11,0 - bne 7f + mfspr r11, SPRN_SPRG_THREAD + lwz r11, RTAS_SP(r11) + cmpwi cr1, r11, 0 + bne cr1, 7f #endif /* CONFIG_PPC_CHRP */ EXCEPTION_PROLOG_1 7: EXCEPTION_PROLOG_2 addi r3,r1,STACK_FRAME_OVERHEAD #ifdef CONFIG_PPC_CHRP - mfspr r4,SPRN_SPRG_RTAS - cmpwi cr1,r4,0 bne cr1,1f #endif EXC_XFER_STD(0x200, machine_check_exception) @@ -865,8 +863,10 @@ __secondary_start: tophys(r4,r2) addi r4,r4,THREAD /* phys address of our thread_struct */ mtspr SPRN_SPRG_THREAD,r4 +#ifdef CONFIG_PPC_RTAS li r3,0 - mtspr SPRN_SPRG_RTAS,r3 /* 0 => not in RTAS */ + stw r3, RTAS_SP(r4) /* 0 => not in RTAS */ +#endif /* enable MMU and jump to start_secondary */ li r4,MSR_KERNEL @@ -950,8 +950,10 @@ start_here: tophys(r4,r2) addi r4,r4,THREAD /* init task's THREAD */ mtspr SPRN_SPRG_THREAD,r4 +#ifdef CONFIG_PPC_RTAS li r3,0 - mtspr SPRN_SPRG_RTAS,r3 /* 0 => not in RTAS */ + stw r3, RTAS_SP(r4) /* 0 => not in RTAS */ +#endif /* stack */ lis r1,init_thread_union@ha -- 2.30.2