powerpc/32: Only restore non volatile registers when required

Until now, non volatile registers were restored everytime they
were saved, ie using EXC_XFER_STD meant saving and restoring
them while EXC_XFER_LITE meant neither saving not restoring them.

Now that they are always saved, EXC_XFER_STD means to restore
them and EXC_XFER_LITE means to not restore them.

Most of the users of EXC_XFER_STD only need to retrieve the
non volatile registers. For them there is no need to restore
the non volatile registers as they have not been modified.

Only very few exceptions require non volatile registers restore.

Opencode the few places which require saving of non volatile
registers.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/d1cb12d8023cc6afc1f07150565571373c04945c.1615552867.git.christophe.leroy@csgroup.eu

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 237b753..e6adb68 100644 (file)
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -358,7 +358,6 @@ _ASM_NOKPROBE_SYMBOL(fast_exception_return)
 
        .globl  ret_from_except_full
 ret_from_except_full:
-       REST_NVGPRS(r1)
        /* fall through */
 
        .globl  ret_from_except

diff --git a/arch/powerpc/kernel/head_40x.S b/arch/powerpc/kernel/head_40x.S
index 7270caf..f3e5b46 100644 (file)
--- a/arch/powerpc/kernel/head_40x.S
+++ b/arch/powerpc/kernel/head_40x.S
@@ -228,12 +228,18 @@ _ASM_NOKPROBE_SYMBOL(\name\()_virt)
 /* 0x0600 - Alignment Exception */
        START_EXCEPTION(0x0600, Alignment)
        EXCEPTION_PROLOG 0x600 Alignment handle_dar_dsisr=1
-       EXC_XFER_STD(0x600, alignment_exception)
+       prepare_transfer_to_handler
+       bl      alignment_exception
+       REST_NVGPRS(r1)
+       b       interrupt_return
 
 /* 0x0700 - Program Exception */
        START_EXCEPTION(0x0700, ProgramCheck)
        EXCEPTION_PROLOG 0x700 ProgramCheck handle_dar_dsisr=1
-       EXC_XFER_STD(0x700, program_check_exception)
+       prepare_transfer_to_handler
+       bl      program_check_exception
+       REST_NVGPRS(r1)
+       b       interrupt_return
 
        EXCEPTION(0x0800, Trap_08, unknown_exception, EXC_XFER_STD)
        EXCEPTION(0x0900, Trap_09, unknown_exception, EXC_XFER_STD)

diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index c48de97..86f844e 100644 (file)
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -131,10 +131,18 @@ instruction_counter:
 /* Alignment exception */
        START_EXCEPTION(0x600, Alignment)
        EXCEPTION_PROLOG 0x600 Alignment handle_dar_dsisr=1
-       EXC_XFER_STD(0x600, alignment_exception)
+       prepare_transfer_to_handler
+       bl      alignment_exception
+       REST_NVGPRS(r1)
+       b       interrupt_return
 
 /* Program check exception */
-       EXCEPTION(0x700, ProgramCheck, program_check_exception, EXC_XFER_STD)
+       START_EXCEPTION(0x700, ProgramCheck)
+       EXCEPTION_PROLOG 0x700 ProgramCheck
+       prepare_transfer_to_handler
+       bl      program_check_exception
+       REST_NVGPRS(r1)
+       b       interrupt_return
 
 /* Decrementer */
        EXCEPTION(0x900, Decrementer, timer_interrupt, EXC_XFER_LITE)
@@ -149,7 +157,12 @@ instruction_counter:
 /* On the MPC8xx, this is a software emulation interrupt.  It occurs
  * for all unimplemented and illegal instructions.
  */
-       EXCEPTION(0x1000, SoftEmu, emulation_assist_interrupt, EXC_XFER_STD)
+       START_EXCEPTION(0x1000, SoftEmu)
+       EXCEPTION_PROLOG 0x1000 SoftEmu
+       prepare_transfer_to_handler
+       bl      emulation_assist_interrupt
+       REST_NVGPRS(r1)
+       b       interrupt_return
 
 /*
  * For the MPC8xx, this is a software tablewalk to load the instruction
@@ -348,7 +361,10 @@ DARFixed:/* Return from dcbx instruction bug workaround */
        EXCEPTION_PROLOG_2 0x1c00 DataBreakpoint handle_dar_dsisr=1
        mfspr   r4,SPRN_BAR
        stw     r4,_DAR(r11)
-       EXC_XFER_STD(0x1c00, do_break)
+       prepare_transfer_to_handler
+       bl      do_break
+       REST_NVGPRS(r1)
+       b       interrupt_return
 
 #ifdef CONFIG_PERF_EVENTS
        START_EXCEPTION(0x1d00, InstructionBreakpoint)

diff --git a/arch/powerpc/kernel/head_book3s_32.S b/arch/powerpc/kernel/head_book3s_32.S
index 2b4875c..425a4f2 100644 (file)
--- a/arch/powerpc/kernel/head_book3s_32.S
+++ b/arch/powerpc/kernel/head_book3s_32.S
@@ -300,7 +300,10 @@ ALT_MMU_FTR_SECTION_END_IFSET(MMU_FTR_HPTE_TABLE)
        andis.  r0, r5, DSISR_DABRMATCH@h
        bne-    1f
        EXC_XFER_LITE(0x300, do_page_fault)
-1:     EXC_XFER_STD(0x300, do_break)
+1:     prepare_transfer_to_handler
+       bl      do_break
+       REST_NVGPRS(r1)
+       b       interrupt_return
 
 
 /* Instruction access exception. */
@@ -336,10 +339,18 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_HPTE_TABLE)
 /* Alignment exception */
        START_EXCEPTION(0x600, Alignment)
        EXCEPTION_PROLOG 0x600 Alignment handle_dar_dsisr=1
-       EXC_XFER_STD(0x600, alignment_exception)
+       prepare_transfer_to_handler
+       bl      alignment_exception
+       REST_NVGPRS(r1)
+       b       interrupt_return
 
 /* Program check exception */
-       EXCEPTION(0x700, ProgramCheck, program_check_exception, EXC_XFER_STD)
+       START_EXCEPTION(0x700, ProgramCheck)
+       EXCEPTION_PROLOG 0x700 ProgramCheck
+       prepare_transfer_to_handler
+       bl      program_check_exception
+       REST_NVGPRS(r1)
+       b       interrupt_return
 
 /* Floating-point unavailable */
        START_EXCEPTION(0x800, FPUnavailable)

diff --git a/arch/powerpc/kernel/head_booke.h b/arch/powerpc/kernel/head_booke.h
index 0f02b97..baf1055 100644 (file)
--- a/arch/powerpc/kernel/head_booke.h
+++ b/arch/powerpc/kernel/head_booke.h
@@ -483,14 +483,20 @@ label:
        NORMAL_EXCEPTION_PROLOG(0x600, ALIGNMENT);                    \
        mfspr   r4,SPRN_DEAR;           /* Grab the DEAR and save it */       \
        stw     r4,_DEAR(r11);                                                \
-       EXC_XFER_STD(0x0600, alignment_exception)
+       prepare_transfer_to_handler;                                          \
+       bl      alignment_exception;                                          \
+       REST_NVGPRS(r1);                                                      \
+       b       interrupt_return
 
 #define PROGRAM_EXCEPTION                                                    \
        START_EXCEPTION(Program)                                              \
        NORMAL_EXCEPTION_PROLOG(0x700, PROGRAM);                      \
        mfspr   r4,SPRN_ESR;            /* Grab the ESR and save it */        \
        stw     r4,_ESR(r11);                                                 \
-       EXC_XFER_STD(0x0700, program_check_exception)
+       prepare_transfer_to_handler;                                          \
+       bl      program_check_exception;                                      \
+       REST_NVGPRS(r1);                                                      \
+       b       interrupt_return
 
 #define DECREMENTER_EXCEPTION                                                \
        START_EXCEPTION(Decrementer)                                          \

diff --git a/arch/powerpc/kernel/head_fsl_booke.S b/arch/powerpc/kernel/head_fsl_booke.S
index bf2730b..210871b 100644 (file)
--- a/arch/powerpc/kernel/head_fsl_booke.S
+++ b/arch/powerpc/kernel/head_fsl_booke.S
@@ -625,12 +625,20 @@ END_BTB_FLUSH_SECTION
 
        /* SPE Floating Point Data */
 #ifdef CONFIG_SPE
-       EXCEPTION(0x2030, SPE_FP_DATA, SPEFloatingPointData,
-                 SPEFloatingPointException, EXC_XFER_STD)
+       START_EXCEPTION(SPEFloatingPointData)
+       NORMAL_EXCEPTION_PROLOG(0x2030, SPE_FP_DATA)
+       prepare_transfer_to_handler
+       bl      SPEFloatingPointException
+       REST_NVGPRS(r1)
+       b       interrupt_return
 
        /* SPE Floating Point Round */
-       EXCEPTION(0x2050, SPE_FP_ROUND, SPEFloatingPointRound, \
-                 SPEFloatingPointRoundException, EXC_XFER_STD)
+       START_EXCEPTION(SPEFloatingPointRound)
+       NORMAL_EXCEPTION_PROLOG(0x2050, SPE_FP_ROUND)
+       prepare_transfer_to_handler
+       bl      SPEFloatingPointRoundException
+       REST_NVGPRS(r1)
+       b       interrupt_return
 #elif defined(CONFIG_SPE_POSSIBLE)
        EXCEPTION(0x2040, SPE_FP_DATA, SPEFloatingPointData,
                  unknown_exception, EXC_XFER_STD)