From 10d91611f426d4bafd2a83d966c36da811b2f7ad Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Sat, 13 Apr 2019 00:30:52 +1000 Subject: powerpc/64s: Reimplement book3s idle code in C Reimplement Book3S idle code in C, moving POWER7/8/9 implementation speific HV idle code to the powernv platform code. Book3S assembly stubs are kept in common code and used only to save the stack frame and non-volatile GPRs before executing architected idle instructions, and restoring the stack and reloading GPRs then returning to C after waking from idle. The complex logic dealing with threads and subcores, locking, SPRs, HMIs, timebase resync, etc., is all done in C which makes it more maintainable. This is not a strict translation to C code, there are some significant differences: - Idle wakeup no longer uses the ->cpu_restore call to reinit SPRs, but saves and restores them itself. - The optimisation where EC=ESL=0 idle modes did not have to save GPRs or change MSR is restored, because it's now simple to do. ESL=1 sleeps that do not lose GPRs can use this optimization too. - KVM secondary entry and cede is now more of a call/return style rather than branchy. nap_state_lost is not required because KVM always returns via NVGPR restoring path. - KVM secondary wakeup from offline sequence is moved entirely into the offline wakeup, which avoids a hwsync in the normal idle wakeup path. Performance measured with context switch ping-pong on different threads or cores, is possibly improved a small amount, 1-3% depending on stop state and core vs thread test for shallow states. Deep states it's in the noise compared with other latencies. KVM improvements: - Idle sleepers now always return to caller rather than branch out to KVM first. - This allows optimisations like very fast return to caller when no state has been lost. - KVM no longer requires nap_state_lost because it controls NVGPR save/restore itself on the way in and out. - The heavy idle wakeup KVM request check can be moved out of the normal host idle code and into the not-performance-critical offline code. - KVM nap code now returns from where it is called, which makes the flow a bit easier to follow. Reviewed-by: Gautham R. Shenoy Signed-off-by: Nicholas Piggin [mpe: Squash the KVM changes in] Signed-off-by: Michael Ellerman --- arch/powerpc/kvm/book3s_hv_rmhandlers.S | 118 +++++++++++++++++++------------- 1 file changed, 72 insertions(+), 46 deletions(-) (limited to 'arch/powerpc/kvm') diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S index 139027c62dc2..dd014308f065 100644 --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S @@ -35,6 +35,7 @@ #include #include #include +#include /* Sign-extend HDEC if not on POWER9 */ #define EXTEND_HDEC(reg) \ @@ -45,6 +46,7 @@ END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_300) /* Values in HSTATE_NAPPING(r13) */ #define NAPPING_CEDE 1 #define NAPPING_NOVCPU 2 +#define NAPPING_UNSPLIT 3 /* Stack frame offsets for kvmppc_hv_entry */ #define SFS 208 @@ -290,17 +292,19 @@ kvm_novcpu_exit: b kvmhv_switch_to_host /* - * We come in here when wakened from nap mode. - * Relocation is off and most register values are lost. - * r13 points to the PACA. + * We come in here when wakened from Linux offline idle code. + * Relocation is off * 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 +_GLOBAL(idle_kvm_start_guest) + ld r4,PACAEMERGSP(r13) + mfcr r5 + mflr r0 + std r1,0(r4) + std r5,8(r4) + std r0,16(r4) + subi r1,r4,STACK_FRAME_OVERHEAD + SAVE_NVGPRS(r1) /* * Could avoid this and pass it through in r3. For now, @@ -308,27 +312,23 @@ kvm_start_guest: */ mtspr SPRN_SRR1,r3 - ld r2,PACATOC(r13) - li r0,0 stb r0,PACA_FTRACE_ENABLED(r13) li r0,KVM_HWTHREAD_IN_KVM stb r0,HSTATE_HWTHREAD_STATE(r13) - /* NV GPR values from power7_idle() will no longer be valid */ - li r0,1 - stb r0,PACA_NAPSTATELOST(r13) - - /* were we napping due to cede? */ + /* kvm cede / napping does not come through here */ lbz r0,HSTATE_NAPPING(r13) - cmpwi r0,NAPPING_CEDE - beq kvm_end_cede - cmpwi r0,NAPPING_NOVCPU - beq kvm_novcpu_wakeup + twnei r0,0 + + b 1f - ld r1,PACAEMERGSP(r13) - subi r1,r1,STACK_FRAME_OVERHEAD +kvm_unsplit_wakeup: + li r0, 0 + stb r0, HSTATE_NAPPING(r13) + +1: /* * We weren't napping due to cede, so this must be a secondary @@ -437,19 +437,25 @@ kvm_no_guest: lbz r3, HSTATE_HWTHREAD_REQ(r13) cmpwi r3, 0 bne 54f -/* - * We jump to pnv_wakeup_loss, which will return to the caller - * of power7_nap in the powernv cpu offline loop. The value we - * put in r3 becomes the return value for power7_nap. pnv_wakeup_loss - * requires SRR1 in r12. - */ + + /* + * Jump to idle_return_gpr_loss, which returns to the + * idle_kvm_start_guest caller. + */ li r3, LPCR_PECE0 mfspr r4, SPRN_LPCR rlwimi r4, r3, 0, LPCR_PECE0 | LPCR_PECE1 mtspr SPRN_LPCR, r4 - li r3, 0 - mfspr r12,SPRN_SRR1 - b pnv_wakeup_loss + /* set up r3 for return */ + mfspr r3,SPRN_SRR1 + REST_NVGPRS(r1) + addi r1, r1, STACK_FRAME_OVERHEAD + ld r0, 16(r1) + ld r5, 8(r1) + ld r1, 0(r1) + mtlr r0 + mtcr r5 + blr 53: HMT_LOW ld r5, HSTATE_KVM_VCORE(r13) @@ -534,6 +540,8 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S) lbz r0, KVM_SPLIT_DO_NAP(r3) cmpwi r0, 0 beq 57f + li r3, NAPPING_UNSPLIT + stb r3, HSTATE_NAPPING(r13) li r3, (LPCR_PECEDH | LPCR_PECE0) >> 4 mfspr r5, SPRN_LPCR rlwimi r5, r3, 4, (LPCR_PECEDP | LPCR_PECEDH | LPCR_PECE0 | LPCR_PECE1) @@ -2657,6 +2665,9 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300) lis r3, LPCR_PECEDP@h /* Do wake on privileged doorbell */ + /* Go back to host stack */ + ld r1, HSTATE_HOST_R1(r13) + /* * Take a nap until a decrementer or external or doobell interrupt * occurs, with PECE1 and PECE0 set in LPCR. @@ -2685,26 +2696,42 @@ BEGIN_FTR_SECTION * requested level = 0 (just stop dispatching) */ lis r3, (PSSCR_EC | PSSCR_ESL)@h - mtspr SPRN_PSSCR, r3 /* Set LPCR_PECE_HVEE bit to enable wakeup by HV interrupts */ li r4, LPCR_PECE_HVEE@higher sldi r4, r4, 32 or r5, r5, r4 -END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300) +FTR_SECTION_ELSE + li r3, PNV_THREAD_NAP +ALT_FTR_SECTION_END_IFSET(CPU_FTR_ARCH_300) mtspr SPRN_LPCR,r5 isync - li r0, 0 - std r0, HSTATE_SCRATCH0(r13) - ptesync - ld r0, HSTATE_SCRATCH0(r13) -1: cmpd r0, r0 - bne 1b + BEGIN_FTR_SECTION - nap + bl isa300_idle_stop_mayloss FTR_SECTION_ELSE - PPC_STOP -ALT_FTR_SECTION_END_IFCLR(CPU_FTR_ARCH_300) - b . + bl isa206_idle_insn_mayloss +ALT_FTR_SECTION_END_IFSET(CPU_FTR_ARCH_300) + + mfspr r0, SPRN_CTRLF + ori r0, r0, 1 + mtspr SPRN_CTRLT, r0 + + mtspr SPRN_SRR1, r3 + + li r0, 0 + stb r0, PACA_FTRACE_ENABLED(r13) + + li r0, KVM_HWTHREAD_IN_KVM + stb r0, HSTATE_HWTHREAD_STATE(r13) + + lbz r0, HSTATE_NAPPING(r13) + cmpwi r0, NAPPING_CEDE + beq kvm_end_cede + cmpwi r0, NAPPING_NOVCPU + beq kvm_novcpu_wakeup + cmpwi r0, NAPPING_UNSPLIT + beq kvm_unsplit_wakeup + twi 31,0,0 /* Nap state must not be zero */ 33: mr r4, r3 li r3, 0 @@ -2712,12 +2739,11 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_ARCH_300) b 34f kvm_end_cede: + /* Woken by external or decrementer interrupt */ + /* get vcpu pointer */ ld r4, HSTATE_KVM_VCPU(r13) - /* Woken by external or decrementer interrupt */ - ld r1, HSTATE_HOST_R1(r13) - #ifdef CONFIG_KVM_BOOK3S_HV_EXIT_TIMING addi r3, r4, VCPU_TB_RMINTR bl kvmhv_accumulate_time -- cgit v1.2.3