[PATCH 08/14] powerpc/64s: idle avoid SRR usage in idle sleep/wake paths
Nicholas Piggin
npiggin at gmail.com
Fri Jun 9 01:51:07 AEST 2017
Idle code now always runs at the 0xc... effective address whether
in real or virtual mode. This means rfid can be ditched, along
with a lot of SRR manipulations.
In the wakeup path, carry SRR1 around in r12. Use mtmsrd to change
MSR states as required.
This also balances the return prediction for the idle call, by
doing blr rather than rfid to return to the idle caller.
On POWER9, 2-process context switch on different cores, with snooze
disabled, increases performance by 2%.
---
arch/powerpc/kernel/exceptions-64s.S | 1 +
arch/powerpc/kernel/idle_book3s.S | 57 +++++++++++++++------------------
arch/powerpc/kvm/book3s_hv_rmhandlers.S | 8 ++++-
3 files changed, 33 insertions(+), 33 deletions(-)
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 153cd967554a..eb703c20f4ad 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -130,6 +130,7 @@ EXC_VIRT_NONE(0x4100, 0x100)
#ifdef CONFIG_PPC_P7_NAP
EXC_COMMON_BEGIN(system_reset_idle_common)
+ mfspr r12,SPRN_SRR1
b pnv_powersave_wakeup
#endif
diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
index c7edb374d1aa..2efb88da8ba3 100644
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -108,7 +108,7 @@ core_idle_lock_held:
* r3 - PNV_THREAD_NAP/SLEEP/WINKLE in POWER8
* - Requested PSSCR value in POWER9
*
- * Address of idle handler to 'rfid' to in r4
+ * Address of idle handler to branch to in realmode in r4
*/
pnv_powersave_common:
/* Use r3 to pass state nap/sleep/winkle */
@@ -118,14 +118,14 @@ pnv_powersave_common:
* need to save PC, some CR bits and the NV GPRs,
* but for now an interrupt frame will do.
*/
+ mtctr r4
+
mflr r0
std r0,16(r1)
stdu r1,-INT_FRAME_SIZE(r1)
std r0,_LINK(r1)
std r0,_NIP(r1)
- mfmsr r9
-
/* We haven't lost state ... yet */
li r0,0
stb r0,PACA_NAPSTATELOST(r13)
@@ -135,7 +135,6 @@ pnv_powersave_common:
SAVE_NVGPRS(r1)
mfcr r5
std r5,_CCR(r1)
- std r9,_MSR(r1)
std r1,PACAR1(r13)
/*
@@ -145,12 +144,8 @@ pnv_powersave_common:
* the MMU context to the guest.
*/
LOAD_REG_IMMEDIATE(r7, MSR_IDLE)
- li r6, MSR_RI
- andc r6, r9, r6
- mtmsrd r6, 1 /* clear RI before setting SRR0/1 */
- mtspr SPRN_SRR0, r4
- mtspr SPRN_SRR1, r7
- rfid
+ mtmsrd r7,0
+ bctr
.globl pnv_enter_arch207_idle_mode
pnv_enter_arch207_idle_mode:
@@ -302,11 +297,10 @@ _GLOBAL(power7_idle_insn)
b pnv_powersave_common
#define CHECK_HMI_INTERRUPT \
- mfspr r0,SPRN_SRR1; \
BEGIN_FTR_SECTION_NESTED(66); \
- rlwinm r0,r0,45-31,0xf; /* extract wake reason field (P8) */ \
+ rlwinm r0,r12,45-31,0xf; /* extract wake reason field (P8) */ \
FTR_SECTION_ELSE_NESTED(66); \
- rlwinm r0,r0,45-31,0xe; /* P7 wake reason field is 3 bits */ \
+ rlwinm r0,r12,45-31,0xe; /* P7 wake reason field is 3 bits */ \
ALT_FTR_SECTION_END_NESTED_IFSET(CPU_FTR_ARCH_207S, 66); \
cmpwi r0,0xa; /* Hypervisor maintenance ? */ \
bne 20f; \
@@ -384,17 +378,17 @@ pnv_powersave_wakeup_mce:
/*
* Now put the original SRR1 with SRR1_WAKEMCE_RESVD as the wake
- * reason into SRR1, which allows reuse of the system reset wakeup
+ * reason into r12, which allows reuse of the system reset wakeup
* code without being mistaken for another type of wakeup.
*/
- oris r3,r3,SRR1_WAKEMCE_RESVD at h
- mtspr SPRN_SRR1,r3
+ oris r12,r3,SRR1_WAKEMCE_RESVD at h
b pnv_powersave_wakeup
/*
* Called from reset vector for powersave wakeups.
* cr3 - set to gt if waking up with partial/complete hypervisor state loss
+ * r12 - SRR1
*/
.global pnv_powersave_wakeup
pnv_powersave_wakeup:
@@ -404,8 +398,10 @@ BEGIN_FTR_SECTION
BEGIN_FTR_SECTION_NESTED(70)
bl power9_dd1_recover_paca
END_FTR_SECTION_NESTED_IFSET(CPU_FTR_POWER9_DD1, 70)
+ ld r1,PACAR1(r13)
bl pnv_restore_hyp_resource_arch300
FTR_SECTION_ELSE
+ ld r1,PACAR1(r13)
bl pnv_restore_hyp_resource_arch207
ALT_FTR_SECTION_END_IFSET(CPU_FTR_ARCH_300)
@@ -425,7 +421,7 @@ ALT_FTR_SECTION_END_IFSET(CPU_FTR_ARCH_300)
#endif
/* Return SRR1 from power7_nap() */
- mfspr r3,SPRN_SRR1
+ mr r3,r12
blt cr3,pnv_wakeup_noloss
b pnv_wakeup_loss
@@ -489,7 +485,6 @@ pnv_restore_hyp_resource_arch207:
* r4 - PACA_THREAD_IDLE_STATE
*/
pnv_wakeup_tb_loss:
- ld r1,PACAR1(r13)
/*
* Before entering any idle state, the NVGPRs are saved in the stack.
* If there was a state loss, or PACA_NAPSTATELOST was set, then the
@@ -515,9 +510,9 @@ pnv_wakeup_tb_loss:
* is required to return back to reset vector after hypervisor state
* restore is complete.
*/
+ mr r19,r12
mr r18,r4
mflr r17
- mfspr r16,SPRN_SRR1
BEGIN_FTR_SECTION
CHECK_HMI_INTERRUPT
END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
@@ -762,7 +757,7 @@ no_segments:
hypervisor_state_restored:
- mtspr SPRN_SRR1,r16
+ mr r12,r19
mtlr r17
blr /* return to pnv_powersave_wakeup */
@@ -778,20 +773,19 @@ fastsleep_workaround_at_exit:
*/
.global pnv_wakeup_loss
pnv_wakeup_loss:
- ld r1,PACAR1(r13)
BEGIN_FTR_SECTION
CHECK_HMI_INTERRUPT
END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
REST_NVGPRS(r1)
REST_GPR(2, r1)
+ ld r4,PACAKMSR(r13)
+ ld r5,_LINK(r1)
ld r6,_CCR(r1)
- ld r4,_MSR(r1)
- ld r5,_NIP(r1)
addi r1,r1,INT_FRAME_SIZE
+ mtlr r5
mtcr r6
- mtspr SPRN_SRR1,r4
- mtspr SPRN_SRR0,r5
- rfid
+ mtmsrd r4
+ blr
/*
* R3 here contains the value that will be returned to the caller
@@ -804,12 +798,11 @@ pnv_wakeup_noloss:
BEGIN_FTR_SECTION
CHECK_HMI_INTERRUPT
END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
- ld r1,PACAR1(r13)
- ld r6,_CCR(r1)
- ld r4,_MSR(r1)
+ ld r4,PACAKMSR(r13)
ld r5,_NIP(r1)
+ ld r6,_CCR(r1)
addi r1,r1,INT_FRAME_SIZE
+ mtlr r5
mtcr r6
- mtspr SPRN_SRR1,r4
- mtspr SPRN_SRR0,r5
- rfid
+ mtmsrd r4
+ blr
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index bdb3f76ceb6b..eb5b78b6bacf 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -329,15 +329,21 @@ kvm_novcpu_exit:
* We come in here when wakened from nap mode.
* Relocation is off and most register values are lost.
* r13 points to the PACA.
+ * r3 contains the SRR1 wakeup value, SRR1 is trashed.
*/
.globl kvm_start_guest
kvm_start_guest:
-
/* Set runlatch bit the minute you wake up from nap */
mfspr r0, SPRN_CTRLF
ori r0, r0, 1
mtspr SPRN_CTRLT, r0
+ /*
+ * Could avoid this and pass it through in r3. For now,
+ * code expects it to be in SRR1.
+ */
+ mtspr r3,SPRN_SRR1
+
ld r2,PACATOC(r13)
li r0,KVM_HWTHREAD_IN_KVM
--
2.11.0
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