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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 <ego@linux.vnet.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Squash the KVM changes in]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Nicholas Piggin 2019-04-13 00:30:52 +10:00 committed by Michael Ellerman
parent c1fe190c06
commit 10d91611f4
12 changed files with 977 additions and 1226 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
arch/powerpc/include/asm/cpuidle.h
View File

@ -27,10 +27,11 @@
* the THREAD_WINKLE_BITS are set, which indicate which threads have not
* yet woken from the winkle state.
*/
#define PNV_CORE_IDLE_LOCK_BIT 0x10000000
#define NR_PNV_CORE_IDLE_LOCK_BIT 28
#define PNV_CORE_IDLE_LOCK_BIT (1ULL << NR_PNV_CORE_IDLE_LOCK_BIT)
#define PNV_CORE_IDLE_WINKLE_COUNT_SHIFT 16
#define PNV_CORE_IDLE_WINKLE_COUNT 0x00010000
#define PNV_CORE_IDLE_WINKLE_COUNT_ALL_BIT 0x00080000
#define PNV_CORE_IDLE_WINKLE_COUNT_BITS 0x000F0000
#define PNV_CORE_IDLE_THREAD_WINKLE_BITS_SHIFT 8
#define PNV_CORE_IDLE_THREAD_WINKLE_BITS 0x0000FF00
@ -68,16 +69,6 @@
#define ERR_DEEP_STATE_ESL_MISMATCH -2
#ifndef __ASSEMBLY__
/* Additional SPRs that need to be saved/restored during stop */
struct stop_sprs {
u64 pid;
u64 ldbar;
u64 fscr;
u64 hfscr;
u64 mmcr1;
u64 mmcr2;
u64 mmcra;
};
#define PNV_IDLE_NAME_LEN 16
struct pnv_idle_states_t {
@ -92,10 +83,6 @@ struct pnv_idle_states_t {
extern struct pnv_idle_states_t *pnv_idle_states;
extern int nr_pnv_idle_states;
extern u32 pnv_fastsleep_workaround_at_entry[];
extern u32 pnv_fastsleep_workaround_at_exit[];
extern u64 pnv_first_deep_stop_state;
unsigned long pnv_cpu_offline(unsigned int cpu);
int validate_psscr_val_mask(u64 *psscr_val, u64 *psscr_mask, u32 flags);

38
arch/powerpc/include/asm/paca.h
View File

@ -173,7 +173,6 @@ struct paca_struct {
u8 irq_happened; /* irq happened while soft-disabled */
u8 io_sync; /* writel() needs spin_unlock sync */
u8 irq_work_pending; /* IRQ_WORK interrupt while soft-disable */
u8 nap_state_lost; /* NV GPR values lost in power7_idle */
#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
u8 pmcregs_in_use; /* pseries puts this in lppaca */
#endif
@ -183,23 +182,28 @@ struct paca_struct {
#endif
#ifdef CONFIG_PPC_POWERNV
/* Per-core mask tracking idle threads and a lock bit-[L][TTTTTTTT] */
u32 *core_idle_state_ptr;
u8 thread_idle_state; /* PNV_THREAD_RUNNING/NAP/SLEEP */
/* Mask to indicate thread id in core */
u8 thread_mask;
/* Mask to denote subcore sibling threads */
u8 subcore_sibling_mask;
/* Flag to request this thread not to stop */
atomic_t dont_stop;
/* The PSSCR value that the kernel requested before going to stop */
u64 requested_psscr;
/* PowerNV idle fields */
/* PNV_CORE_IDLE_* bits, all siblings work on thread 0 paca */
unsigned long idle_state;
union {
/* P7/P8 specific fields */
struct {
/* PNV_THREAD_RUNNING/NAP/SLEEP */
u8 thread_idle_state;
/* Mask to denote subcore sibling threads */
u8 subcore_sibling_mask;
};
/*
* Save area for additional SPRs that need to be
* saved/restored during cpuidle stop.
*/
struct stop_sprs stop_sprs;
/* P9 specific fields */
struct {
#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
/* The PSSCR value that the kernel requested before going to stop */
u64 requested_psscr;
/* Flag to request this thread not to stop */
atomic_t dont_stop;
#endif
};
};
#endif
#ifdef CONFIG_PPC_BOOK3S_64

9
arch/powerpc/include/asm/processor.h
View File

@ -411,14 +411,17 @@ static inline unsigned long get_clean_sp(unsigned long sp, int is_32)
}
#endif
/* asm stubs */
extern unsigned long isa300_idle_stop_noloss(unsigned long psscr_val);
extern unsigned long isa300_idle_stop_mayloss(unsigned long psscr_val);
extern unsigned long isa206_idle_insn_mayloss(unsigned long type);
extern unsigned long cpuidle_disable;
enum idle_boot_override {IDLE_NO_OVERRIDE = 0, IDLE_POWERSAVE_OFF};
extern int powersave_nap; /* set if nap mode can be used in idle loop */
extern unsigned long power7_idle_insn(unsigned long type); /* PNV_THREAD_NAP/etc*/
extern void power7_idle_type(unsigned long type);
extern unsigned long power9_idle_stop(unsigned long psscr_val);
extern unsigned long power9_offline_stop(unsigned long psscr_val);
extern void power9_idle_type(unsigned long stop_psscr_val,
unsigned long stop_psscr_mask);

8
arch/powerpc/include/asm/reg.h
View File

@ -168,6 +168,7 @@
#define PSSCR_ESL 0x00200000 /* Enable State Loss */
#define PSSCR_SD 0x00400000 /* Status Disable */
#define PSSCR_PLS 0xf000000000000000 /* Power-saving Level Status */
#define PSSCR_PLS_SHIFT 60
#define PSSCR_GUEST_VIS 0xf0000000000003ffUL /* Guest-visible PSSCR fields */
#define PSSCR_FAKE_SUSPEND 0x00000400 /* Fake-suspend bit (P9 DD2.2) */
#define PSSCR_FAKE_SUSPEND_LG 10 /* Fake-suspend bit position */
@ -758,10 +759,9 @@
#define SRR1_WAKERESET 0x00100000 /* System reset */
#define SRR1_WAKEHDBELL 0x000c0000 /* Hypervisor doorbell on P8 */
#define SRR1_WAKESTATE 0x00030000 /* Powersave exit mask [46:47] */
#define SRR1_WS_DEEPEST 0x00030000 /* Some resources not maintained,
* may not be recoverable */
#define SRR1_WS_DEEPER 0x00020000 /* Some resources not maintained */
#define SRR1_WS_DEEP 0x00010000 /* All resources maintained */
#define SRR1_WS_HVLOSS 0x00030000 /* HV resources not maintained */
#define SRR1_WS_GPRLOSS 0x00020000 /* GPRs not maintained */
#define SRR1_WS_NOLOSS 0x00010000 /* All resources maintained */
#define SRR1_PROGTM 0x00200000 /* TM Bad Thing */
#define SRR1_PROGFPE 0x00100000 /* Floating Point Enabled */
#define SRR1_PROGILL 0x00080000 /* Illegal instruction */

18
arch/powerpc/kernel/asm-offsets.c
View File

@ -268,7 +268,6 @@ int main(void)
OFFSET(ACCOUNT_USER_TIME, paca_struct, accounting.utime);
OFFSET(ACCOUNT_SYSTEM_TIME, paca_struct, accounting.stime);
OFFSET(PACA_TRAP_SAVE, paca_struct, trap_save);
OFFSET(PACA_NAPSTATELOST, paca_struct, nap_state_lost);
OFFSET(PACA_SPRG_VDSO, paca_struct, sprg_vdso);
#else /* CONFIG_PPC64 */
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
@ -766,23 +765,6 @@ int main(void)
OFFSET(VCPU_TIMING_LAST_ENTER_TBL, kvm_vcpu, arch.timing_last_enter.tv32.tbl);
#endif
#ifdef CONFIG_PPC_POWERNV
OFFSET(PACA_CORE_IDLE_STATE_PTR, paca_struct, core_idle_state_ptr);
OFFSET(PACA_THREAD_IDLE_STATE, paca_struct, thread_idle_state);
OFFSET(PACA_THREAD_MASK, paca_struct, thread_mask);
OFFSET(PACA_SUBCORE_SIBLING_MASK, paca_struct, subcore_sibling_mask);
OFFSET(PACA_REQ_PSSCR, paca_struct, requested_psscr);
OFFSET(PACA_DONT_STOP, paca_struct, dont_stop);
#define STOP_SPR(x, f) OFFSET(x, paca_struct, stop_sprs.f)
STOP_SPR(STOP_PID, pid);
STOP_SPR(STOP_LDBAR, ldbar);
STOP_SPR(STOP_FSCR, fscr);
STOP_SPR(STOP_HFSCR, hfscr);
STOP_SPR(STOP_MMCR1, mmcr1);
STOP_SPR(STOP_MMCR2, mmcr2);
STOP_SPR(STOP_MMCRA, mmcra);
#endif
DEFINE(PPC_DBELL_SERVER, PPC_DBELL_SERVER);
DEFINE(PPC_DBELL_MSGTYPE, PPC_DBELL_MSGTYPE);

23
arch/powerpc/kernel/exceptions-64s.S
View File

@ -120,7 +120,9 @@ EXC_VIRT_NONE(0x4000, 0x100)
mfspr r10,SPRN_SRR1 ; \
rlwinm. r10,r10,47-31,30,31 ; \
beq- 1f ; \
cmpwi cr3,r10,2 ; \
cmpwi cr1,r10,2 ; \
mfspr r3,SPRN_SRR1 ; \
bltlr cr1 ; /* no state loss, return to idle caller */ \
BRANCH_TO_C000(r10, system_reset_idle_common) ; \
1: \
KVMTEST_PR(n) ; \
@ -144,8 +146,11 @@ TRAMP_KVM(PACA_EXNMI, 0x100)
#ifdef CONFIG_PPC_P7_NAP
EXC_COMMON_BEGIN(system_reset_idle_common)
mfspr r12,SPRN_SRR1
b pnv_powersave_wakeup
/*
* This must be a direct branch (without linker branch stub) because
* we can not use TOC at this point as r2 may not be restored yet.
*/
b idle_return_gpr_loss
#endif
/*
@ -427,17 +432,17 @@ EXC_COMMON_BEGIN(machine_check_idle_common)
* Then decrement MCE nesting after finishing with the stack.
*/
ld r3,_MSR(r1)
ld r4,_LINK(r1)
lhz r11,PACA_IN_MCE(r13)
subi r11,r11,1
sth r11,PACA_IN_MCE(r13)
/* Turn off the RI bit because SRR1 is used by idle wakeup code. */
/* Recoverability could be improved by reducing the use of SRR1. */
li r11,0
mtmsrd r11,1
b pnv_powersave_wakeup_mce
mtlr r4
rlwinm r10,r3,47-31,30,31
cmpwi cr1,r10,2
bltlr cr1 /* no state loss, return to idle caller */
b idle_return_gpr_loss
#endif
/*
* Handle machine check early in real mode. We come here with

1068
arch/powerpc/kernel/idle_book3s.S
View File

File diff suppressed because it is too large Load Diff

4
arch/powerpc/kernel/setup-common.c
View File

@ -401,8 +401,8 @@ void __init check_for_initrd(void)
#ifdef CONFIG_SMP
int threads_per_core, threads_per_subcore, threads_shift;
cpumask_t threads_core_mask;
int threads_per_core, threads_per_subcore, threads_shift __read_mostly;
cpumask_t threads_core_mask __read_mostly;
EXPORT_SYMBOL_GPL(threads_per_core);
EXPORT_SYMBOL_GPL(threads_per_subcore);
EXPORT_SYMBOL_GPL(threads_shift);

118
arch/powerpc/kvm/book3s_hv_rmhandlers.S
View File

@ -35,6 +35,7 @@
#include <asm/thread_info.h>
#include <asm/asm-compat.h>
#include <asm/feature-fixups.h>
#include <asm/cpuidle.h>
/* 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
ld r1,PACAEMERGSP(r13)
subi r1,r1,STACK_FRAME_OVERHEAD
b 1f
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

872
arch/powerpc/platforms/powernv/idle.c
View File

File diff suppressed because it is too large Load Diff

2
arch/powerpc/platforms/powernv/subcore.c
View File

@ -183,7 +183,7 @@ static void unsplit_core(void)
cpu = smp_processor_id();
if (cpu_thread_in_core(cpu) != 0) {
while (mfspr(SPRN_HID0) & mask)
power7_idle_insn(PNV_THREAD_NAP);
power7_idle_type(PNV_THREAD_NAP);
per_cpu(split_state, cpu).step = SYNC_STEP_UNSPLIT;
return;

24
arch/powerpc/xmon/xmon.c
View File

@ -2431,7 +2431,6 @@ static void dump_one_paca(int cpu)
DUMP(p, irq_happened, "%#-*x");
DUMP(p, io_sync, "%#-*x");
DUMP(p, irq_work_pending, "%#-*x");
DUMP(p, nap_state_lost, "%#-*x");
DUMP(p, sprg_vdso, "%#-*llx");
#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
@ -2439,19 +2438,16 @@ static void dump_one_paca(int cpu)
#endif
#ifdef CONFIG_PPC_POWERNV
DUMP(p, core_idle_state_ptr, "%-*px");
DUMP(p, thread_idle_state, "%#-*x");
DUMP(p, thread_mask, "%#-*x");
DUMP(p, subcore_sibling_mask, "%#-*x");
DUMP(p, requested_psscr, "%#-*llx");
DUMP(p, stop_sprs.pid, "%#-*llx");
DUMP(p, stop_sprs.ldbar, "%#-*llx");
DUMP(p, stop_sprs.fscr, "%#-*llx");
DUMP(p, stop_sprs.hfscr, "%#-*llx");
DUMP(p, stop_sprs.mmcr1, "%#-*llx");
DUMP(p, stop_sprs.mmcr2, "%#-*llx");
DUMP(p, stop_sprs.mmcra, "%#-*llx");
DUMP(p, dont_stop.counter, "%#-*x");
DUMP(p, idle_state, "%#-*lx");
if (!early_cpu_has_feature(CPU_FTR_ARCH_300)) {
DUMP(p, thread_idle_state, "%#-*x");
DUMP(p, subcore_sibling_mask, "%#-*x");
} else {
#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
DUMP(p, requested_psscr, "%#-*llx");
DUMP(p, dont_stop.counter, "%#-*x");
#endif
}
#endif
DUMP(p, accounting.utime, "%#-*lx");