[PATCH v2 10/35] powerpc/64s/exception: move real->virt switch into the common handler

From: Michal Suchanek
Date: Tue Nov 26 2019 - 15:15:53 EST

From: Nicholas Piggin <npiggin@xxxxxxxxx>

The real mode interrupt entry points currently use rfid to branch to
the common handler in virtual mode. This is a significant amount of
code, and forces other code (notably the KVM test) to live in the
real mode handler.

In the interest of minimising the amount of code that runs unrelocated
move the switch to virt mode into the common code, and do it with
mtmsrd, which avoids clobbering SRRs (although the post-KVMTEST
performance of real-mode interrupt handlers is not a big concern these
days).

This requires CTR to always be saved (real-mode needs to reach 0xc...)
but that's not a huge impact these days. It could be optimized away in
future.

Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
---
arch/powerpc/include/asm/exception-64s.h | 4 -
arch/powerpc/kernel/exceptions-64s.S | 251 ++++++++++-------------
2 files changed, 109 insertions(+), 146 deletions(-)

diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
index 33f4f72eb035..47bd4ea0837d 100644
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -33,11 +33,7 @@
#include <asm/feature-fixups.h>

/* PACA save area size in u64 units (exgen, exmc, etc) */
-#if defined(CONFIG_RELOCATABLE)
#define EX_SIZE 10
-#else
-#define EX_SIZE 9
-#endif

/*
* maximum recursive depth of MCE exceptions
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index b8588618cdc3..5803ce3b9404 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -32,16 +32,10 @@
#define EX_CCR 52
#define EX_CFAR 56
#define EX_PPR 64
-#if defined(CONFIG_RELOCATABLE)
#define EX_CTR 72
.if EX_SIZE != 10
.error "EX_SIZE is wrong"
.endif
-#else
-.if EX_SIZE != 9
- .error "EX_SIZE is wrong"
-.endif
-#endif

/*
* Following are fixed section helper macros.
@@ -124,22 +118,6 @@ name:
#define EXC_HV 1
#define EXC_STD 0

-#if defined(CONFIG_RELOCATABLE)
-/*
- * If we support interrupts with relocation on AND we're a relocatable kernel,
- * we need to use CTR to get to the 2nd level handler. So, save/restore it
- * when required.
- */
-#define SAVE_CTR(reg, area) mfctr reg ; std reg,area+EX_CTR(r13)
-#define GET_CTR(reg, area) ld reg,area+EX_CTR(r13)
-#define RESTORE_CTR(reg, area) ld reg,area+EX_CTR(r13) ; mtctr reg
-#else
-/* ...else CTR is unused and in register. */
-#define SAVE_CTR(reg, area)
-#define GET_CTR(reg, area) mfctr reg
-#define RESTORE_CTR(reg, area)
-#endif
-
/*
* PPR save/restore macros used in exceptions-64s.S
* Used for P7 or later processors
@@ -199,6 +177,7 @@ END_FTR_SECTION_NESTED(ftr,ftr,943)
#define IVEC .L_IVEC_\name\()
#define IHSRR .L_IHSRR_\name\()
#define IAREA .L_IAREA_\name\()
+#define IVIRT .L_IVIRT_\name\()
#define IISIDE .L_IISIDE_\name\()
#define IDAR .L_IDAR_\name\()
#define IDSISR .L_IDSISR_\name\()
@@ -232,6 +211,9 @@ do_define_int n
.ifndef IAREA
IAREA=PACA_EXGEN
.endif
+ .ifndef IVIRT
+ IVIRT=1
+ .endif
.ifndef IISIDE
IISIDE=0
.endif
@@ -325,7 +307,7 @@ END_FTR_SECTION_NESTED(CPU_FTR_HAS_PPR,CPU_FTR_HAS_PPR,948)
* outside the head section. CONFIG_RELOCATABLE KVM expects CTR
* to be saved in HSTATE_SCRATCH1.
*/
- mfctr r9
+ ld r9,IAREA+EX_CTR(r13)
std r9,HSTATE_SCRATCH1(r13)
__LOAD_FAR_HANDLER(r9, kvmppc_interrupt)
mtctr r9
@@ -362,101 +344,6 @@ END_FTR_SECTION_NESTED(CPU_FTR_HAS_PPR,CPU_FTR_HAS_PPR,948)
.endm
#endif

-.macro INT_SAVE_SRR_AND_JUMP label, hsrr, set_ri
- ld r10,PACAKMSR(r13) /* get MSR value for kernel */
- .if ! \set_ri
- xori r10,r10,MSR_RI /* Clear MSR_RI */
- .endif
- .if \hsrr == EXC_HV_OR_STD
- BEGIN_FTR_SECTION
- mfspr r11,SPRN_HSRR0 /* save HSRR0 */
- mfspr r12,SPRN_HSRR1 /* and HSRR1 */
- mtspr SPRN_HSRR1,r10
- FTR_SECTION_ELSE
- mfspr r11,SPRN_SRR0 /* save SRR0 */
- mfspr r12,SPRN_SRR1 /* and SRR1 */
- mtspr SPRN_SRR1,r10
- ALT_FTR_SECTION_END_IFSET(CPU_FTR_HVMODE | CPU_FTR_ARCH_206)
- .elseif \hsrr
- mfspr r11,SPRN_HSRR0 /* save HSRR0 */
- mfspr r12,SPRN_HSRR1 /* and HSRR1 */
- mtspr SPRN_HSRR1,r10
- .else
- mfspr r11,SPRN_SRR0 /* save SRR0 */
- mfspr r12,SPRN_SRR1 /* and SRR1 */
- mtspr SPRN_SRR1,r10
- .endif
- LOAD_HANDLER(r10, \label\())
- .if \hsrr == EXC_HV_OR_STD
- BEGIN_FTR_SECTION
- mtspr SPRN_HSRR0,r10
- HRFI_TO_KERNEL
- FTR_SECTION_ELSE
- mtspr SPRN_SRR0,r10
- RFI_TO_KERNEL
- ALT_FTR_SECTION_END_IFSET(CPU_FTR_HVMODE | CPU_FTR_ARCH_206)
- .elseif \hsrr
- mtspr SPRN_HSRR0,r10
- HRFI_TO_KERNEL
- .else
- mtspr SPRN_SRR0,r10
- RFI_TO_KERNEL
- .endif
- b . /* prevent speculative execution */
-.endm
-
-/* INT_SAVE_SRR_AND_JUMP works for real or virt, this is faster but virt only */
-.macro INT_VIRT_SAVE_SRR_AND_JUMP label, hsrr
-#ifdef CONFIG_RELOCATABLE
- .if \hsrr == EXC_HV_OR_STD
- BEGIN_FTR_SECTION
- mfspr r11,SPRN_HSRR0 /* save HSRR0 */
- FTR_SECTION_ELSE
- mfspr r11,SPRN_SRR0 /* save SRR0 */
- ALT_FTR_SECTION_END_IFSET(CPU_FTR_HVMODE | CPU_FTR_ARCH_206)
- .elseif \hsrr
- mfspr r11,SPRN_HSRR0 /* save HSRR0 */
- .else
- mfspr r11,SPRN_SRR0 /* save SRR0 */
- .endif
- LOAD_HANDLER(r12, \label\())
- mtctr r12
- .if \hsrr == EXC_HV_OR_STD
- BEGIN_FTR_SECTION
- mfspr r12,SPRN_HSRR1 /* and HSRR1 */
- FTR_SECTION_ELSE
- mfspr r12,SPRN_SRR1 /* and HSRR1 */
- ALT_FTR_SECTION_END_IFSET(CPU_FTR_HVMODE | CPU_FTR_ARCH_206)
- .elseif \hsrr
- mfspr r12,SPRN_HSRR1 /* and HSRR1 */
- .else
- mfspr r12,SPRN_SRR1 /* and HSRR1 */
- .endif
- li r10,MSR_RI
- mtmsrd r10,1 /* Set RI (EE=0) */
- bctr
-#else
- .if \hsrr == EXC_HV_OR_STD
- BEGIN_FTR_SECTION
- mfspr r11,SPRN_HSRR0 /* save HSRR0 */
- mfspr r12,SPRN_HSRR1 /* and HSRR1 */
- FTR_SECTION_ELSE
- mfspr r11,SPRN_SRR0 /* save SRR0 */
- mfspr r12,SPRN_SRR1 /* and SRR1 */
- ALT_FTR_SECTION_END_IFSET(CPU_FTR_HVMODE | CPU_FTR_ARCH_206)
- .elseif \hsrr
- mfspr r11,SPRN_HSRR0 /* save HSRR0 */
- mfspr r12,SPRN_HSRR1 /* and HSRR1 */
- .else
- mfspr r11,SPRN_SRR0 /* save SRR0 */
- mfspr r12,SPRN_SRR1 /* and SRR1 */
- .endif
- li r10,MSR_RI
- mtmsrd r10,1 /* Set RI (EE=0) */
- b \label
-#endif
-.endm
-
/*
* This is the BOOK3S interrupt entry code macro.
*
@@ -477,6 +364,23 @@ END_FTR_SECTION_NESTED(CPU_FTR_HAS_PPR,CPU_FTR_HAS_PPR,948)
* - Fall through and continue executing in real, unrelocated mode.
* This is done if early=2.
*/
+
+.macro GEN_BRANCH_TO_COMMON name, virt
+ .if \virt
+#ifndef CONFIG_RELOCATABLE
+ b \name\()_common_virt
+#else
+ LOAD_HANDLER(r10, \name\()_common_virt)
+ mtctr r10
+ bctr
+#endif
+ .else
+ LOAD_HANDLER(r10, \name\()_common_real)
+ mtctr r10
+ bctr
+ .endif
+.endm
+
.macro GEN_INT_ENTRY name, virt, ool=0
SET_SCRATCH0(r13) /* save r13 */
GET_PACA(r13)
@@ -500,8 +404,10 @@ END_FTR_SECTION_NESTED(CPU_FTR_HAS_PPR,CPU_FTR_HAS_PPR,948)
OPT_SAVE_REG_TO_PACA(IAREA+EX_PPR, r9, CPU_FTR_HAS_PPR)
OPT_SAVE_REG_TO_PACA(IAREA+EX_CFAR, r10, CPU_FTR_CFAR)
INTERRUPT_TO_KERNEL
- SAVE_CTR(r10, IAREA)
+ mfctr r10
+ std r10,IAREA+EX_CTR(r13)
mfcr r9
+
.if (!\virt && IKVM_REAL) || (\virt && IKVM_VIRT)
KVMTEST \name IHSRR IVEC
.endif
@@ -566,27 +472,58 @@ END_FTR_SECTION_NESTED(CPU_FTR_HAS_PPR,CPU_FTR_HAS_PPR,948)
.if IEARLY == 2
/* nothing more */
.elseif IEARLY
- mfctr r10 /* save ctr, even for !RELOCATABLE */
BRANCH_TO_C000(r11, \name\()_common)
- .elseif !\virt
- INT_SAVE_SRR_AND_JUMP \name\()_common, IHSRR, ISET_RI
.else
- INT_VIRT_SAVE_SRR_AND_JUMP \name\()_common, IHSRR
+ .if IHSRR == EXC_HV_OR_STD
+ BEGIN_FTR_SECTION
+ mfspr r11,SPRN_HSRR0 /* save HSRR0 */
+ mfspr r12,SPRN_HSRR1 /* and HSRR1 */
+ FTR_SECTION_ELSE
+ mfspr r11,SPRN_SRR0 /* save SRR0 */
+ mfspr r12,SPRN_SRR1 /* and SRR1 */
+ ALT_FTR_SECTION_END_IFSET(CPU_FTR_HVMODE | CPU_FTR_ARCH_206)
+ .elseif IHSRR
+ mfspr r11,SPRN_HSRR0 /* save HSRR0 */
+ mfspr r12,SPRN_HSRR1 /* and HSRR1 */
+ .else
+ mfspr r11,SPRN_SRR0 /* save SRR0 */
+ mfspr r12,SPRN_SRR1 /* and SRR1 */
.endif
+ GEN_BRANCH_TO_COMMON \name \virt
+ .endif
+
.if \ool
.popsection
.endif
.endm

/*
- * On entry r13 points to the paca, r9-r13 are saved in the paca,
- * r9 contains the saved CR, r11 and r12 contain the saved SRR0 and
- * SRR1, and relocation is on.
- *
- * If stack=0, then the stack is already set in r1, and r1 is saved in r10.
- * PPR save and CPU accounting is not done for the !stack case (XXX why not?)
+ * __GEN_COMMON_ENTRY is required to receive the branch from interrupt
+ * entry, except in the case of the IEARLY handlers.
+ * This switches to virtual mode and sets MSR[RI].
*/
-.macro GEN_COMMON name
+.macro __GEN_COMMON_ENTRY name
+DEFINE_FIXED_SYMBOL(\name\()_common_real)
+\name\()_common_real:
+ ld r10,PACAKMSR(r13) /* get MSR value for kernel */
+ /* MSR[RI] is clear iff using SRR regs */
+ .if IHSRR == EXC_HV_OR_STD
+ BEGIN_FTR_SECTION
+ xori r10,r10,MSR_RI
+ END_FTR_SECTION_IFCLR(CPU_FTR_HVMODE)
+ .elseif ! IHSRR
+ xori r10,r10,MSR_RI
+ .endif
+ mtmsrd r10
+
+ .if IVIRT
+ .balign IFETCH_ALIGN_BYTES
+DEFINE_FIXED_SYMBOL(\name\()_common_virt)
+\name\()_common_virt:
+ .endif /* IVIRT */
+.endm
+
+.macro __GEN_COMMON_BODY name
.if ISTACK
andi. r10,r12,MSR_PR /* See if coming from user */
mr r10,r1 /* Save r1 */
@@ -604,6 +541,11 @@ END_FTR_SECTION_NESTED(CPU_FTR_HAS_PPR,CPU_FTR_HAS_PPR,948)
std r0,GPR0(r1) /* save r0 in stackframe */
std r10,GPR1(r1) /* save r1 in stackframe */

+ .if ISET_RI
+ li r10,MSR_RI
+ mtmsrd r10,1 /* Set MSR_RI */
+ .endif
+
.if ISTACK
.if IKUAP
kuap_save_amr_and_lock r9, r10, cr1, cr0
@@ -654,7 +596,7 @@ BEGIN_FTR_SECTION_NESTED(66)
ld r10,IAREA+EX_CFAR(r13)
std r10,ORIG_GPR3(r1)
END_FTR_SECTION_NESTED(CPU_FTR_CFAR, CPU_FTR_CFAR, 66)
- GET_CTR(r10, IAREA)
+ ld r10,IAREA+EX_CTR(r13)
std r10,_CTR(r1)
std r2,GPR2(r1) /* save r2 in stackframe */
SAVE_4GPRS(3, r1) /* save r3 - r6 in stackframe */
@@ -682,6 +624,19 @@ END_FTR_SECTION_NESTED(CPU_FTR_CFAR, CPU_FTR_CFAR, 66)
.endif
.endm

+/*
+ * On entry r13 points to the paca, r9-r13 are saved in the paca,
+ * r9 contains the saved CR, r11 and r12 contain the saved SRR0 and
+ * SRR1, and relocation is on.
+ *
+ * If stack=0, then the stack is already set in r1, and r1 is saved in r10.
+ * PPR save and CPU accounting is not done for the !stack case (XXX why not?)
+ */
+.macro GEN_COMMON name
+ __GEN_COMMON_ENTRY \name
+ __GEN_COMMON_BODY \name
+.endm
+
/*
* Restore all registers including H/SRR0/1 saved in a stack frame of a
* standard exception.
@@ -834,6 +789,7 @@ EXC_VIRT_NONE(0x4000, 0x100)
INT_DEFINE_BEGIN(system_reset)
IVEC=0x100
IAREA=PACA_EXNMI
+ IVIRT=0 /* no virt entry point */
/*
* MSR_RI is not enabled, because PACA_EXNMI and nmi stack is
* being used, so a nested NMI exception would corrupt it.
@@ -913,6 +869,7 @@ TRAMP_REAL_BEGIN(system_reset_fwnmi)
#endif /* CONFIG_PPC_PSERIES */

EXC_COMMON_BEGIN(system_reset_common)
+ __GEN_COMMON_ENTRY system_reset
/*
* Increment paca->in_nmi then enable MSR_RI. SLB or MCE will be able
* to recover, but nested NMI will notice in_nmi and not recover
@@ -928,7 +885,7 @@ EXC_COMMON_BEGIN(system_reset_common)
mr r10,r1
ld r1,PACA_NMI_EMERG_SP(r13)
subi r1,r1,INT_FRAME_SIZE
- GEN_COMMON system_reset
+ __GEN_COMMON_BODY system_reset
bl save_nvgprs
/*
* Set IRQS_ALL_DISABLED unconditionally so arch_irqs_disabled does
@@ -973,6 +930,7 @@ EXC_COMMON_BEGIN(system_reset_common)
INT_DEFINE_BEGIN(machine_check_early)
IVEC=0x200
IAREA=PACA_EXMC
+ IVIRT=0 /* no virt entry point */
/*
* MSR_RI is not enabled, because PACA_EXMC is being used, so a
* nested machine check corrupts it. machine_check_common enables
@@ -990,6 +948,7 @@ INT_DEFINE_END(machine_check_early)
INT_DEFINE_BEGIN(machine_check)
IVEC=0x200
IAREA=PACA_EXMC
+ IVIRT=0 /* no virt entry point */
ISET_RI=0
IDAR=1
IDSISR=1
@@ -1022,7 +981,6 @@ TRAMP_KVM_BEGIN(machine_check_kvm)
EXCEPTION_RESTORE_REGS EXC_STD

EXC_COMMON_BEGIN(machine_check_early_common)
- mtctr r10 /* Restore ctr */
mfspr r11,SPRN_SRR0
mfspr r12,SPRN_SRR1

@@ -1061,7 +1019,7 @@ EXC_COMMON_BEGIN(machine_check_early_common)
bgt cr1,unrecoverable_mce /* Check if we hit limit of 4 */
subi r1,r1,INT_FRAME_SIZE /* alloc stack frame */

- GEN_COMMON machine_check_early
+ __GEN_COMMON_BODY machine_check_early

BEGIN_FTR_SECTION
bl enable_machine_check
@@ -1448,6 +1406,8 @@ EXC_VIRT_END(program_check, 0x4700, 0x100)
TRAMP_KVM_BEGIN(program_check_kvm)
GEN_KVM program_check
EXC_COMMON_BEGIN(program_check_common)
+ __GEN_COMMON_ENTRY program_check
+
/*
* It's possible to receive a TM Bad Thing type program check with
* userspace register values (in particular r1), but with SRR1 reporting
@@ -1473,11 +1433,11 @@ EXC_COMMON_BEGIN(program_check_common)
ld r1,PACAEMERGSP(r13) /* Use emergency stack */
subi r1,r1,INT_FRAME_SIZE /* alloc stack frame */
__ISTACK(program_check)=0
- GEN_COMMON program_check
+ __GEN_COMMON_BODY program_check
b 3f
2:
__ISTACK(program_check)=1
- GEN_COMMON program_check
+ __GEN_COMMON_BODY program_check
3:
bl save_nvgprs
addi r3,r1,STACK_FRAME_OVERHEAD
@@ -1874,14 +1834,13 @@ TRAMP_KVM_BEGIN(hmi_exception_kvm)
GEN_KVM hmi_exception

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 */

- GEN_COMMON hmi_exception_early
+ __GEN_COMMON_BODY hmi_exception_early

addi r3,r1,STACK_FRAME_OVERHEAD
bl hmi_exception_realmode
@@ -2208,7 +2167,9 @@ EXC_REAL_BEGIN(denorm_exception, 0x1500, 0x100)
bne+ denorm_assist
#endif
KVMTEST denorm_exception, EXC_HV, 0x1500
- INT_SAVE_SRR_AND_JUMP denorm_exception_common, EXC_HV, 1
+ mfspr r11,SPRN_HSRR0
+ mfspr r12,SPRN_HSRR1
+ GEN_BRANCH_TO_COMMON denorm_exception, virt=0
EXC_REAL_END(denorm_exception, 0x1500, 0x100)
#ifdef CONFIG_PPC_DENORMALISATION
EXC_VIRT_BEGIN(denorm_exception, 0x5500, 0x100)
@@ -2216,7 +2177,9 @@ EXC_VIRT_BEGIN(denorm_exception, 0x5500, 0x100)
mfspr r10,SPRN_HSRR1
andis. r10,r10,(HSRR1_DENORM)@h /* denorm? */
bne+ denorm_assist
- INT_VIRT_SAVE_SRR_AND_JUMP denorm_exception_common, EXC_HV
+ mfspr r11,SPRN_HSRR0
+ mfspr r12,SPRN_HSRR1
+ GEN_BRANCH_TO_COMMON denorm_exception, virt=1
EXC_VIRT_END(denorm_exception, 0x5500, 0x100)
#else
EXC_VIRT_NONE(0x5500, 0x100)
@@ -2387,7 +2350,11 @@ EXC_VIRT_NONE(0x5800, 0x100)
std r12,PACA_EXGEN+EX_R12(r13); \
GET_SCRATCH0(r10); \
std r10,PACA_EXGEN+EX_R13(r13); \
- INT_SAVE_SRR_AND_JUMP soft_nmi_common, _H, 1
+ mfspr r11,SPRN_SRR0; /* save SRR0 */ \
+ mfspr r12,SPRN_SRR1; /* and SRR1 */ \
+ LOAD_HANDLER(r10, soft_nmi_common); \
+ mtctr r10; \
+ bctr

/*
* Branch to soft_nmi_interrupt using the emergency stack. The emergency
@@ -2403,7 +2370,7 @@ EXC_COMMON_BEGIN(soft_nmi_common)
ld r1,PACAEMERGSP(r13)
subi r1,r1,INT_FRAME_SIZE
__ISTACK(decrementer)=0
- GEN_COMMON decrementer
+ __GEN_COMMON_BODY decrementer
bl save_nvgprs
addi r3,r1,STACK_FRAME_OVERHEAD
bl soft_nmi_interrupt
--
2.23.0