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Message-Id: <c2b0dfd6066db54add31aa67e7291a5106bbad5b.1550745320.git.christophe.leroy@c-s.fr>
Date: Thu, 21 Feb 2019 10:37:54 +0000 (UTC)
From: Christophe Leroy <christophe.leroy@....fr>
To: Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Michael Ellerman <mpe@...erman.id.au>
Cc: linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v2 02/10] 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 <christophe.leroy@....fr>
---
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 0768dfd8a64e..394772b0a6e2 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -1335,7 +1335,7 @@ _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
@@ -1344,7 +1344,8 @@ _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
--
2.13.3
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