KVM: PPC: Book3S HV P9: Optimise timebase reads

Reduce the number of mfTB executed by passing the current timebase
around entry and exit code rather than read it multiple times.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211123095231.1036501-25-npiggin@gmail.com

diff --git a/arch/powerpc/include/asm/kvm_book3s_64.h b/arch/powerpc/include/asm/kvm_book3s_64.h
index fff391b..0a319ed 100644 (file)
--- a/arch/powerpc/include/asm/kvm_book3s_64.h
+++ b/arch/powerpc/include/asm/kvm_book3s_64.h
@@ -154,7 +154,7 @@ static inline bool kvmhv_vcpu_is_radix(struct kvm_vcpu *vcpu)
        return radix;
 }
 
-int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpcr);
+int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpcr, u64 *tb);
 
 #define KVM_DEFAULT_HPT_ORDER  24      /* 16MB HPT by default */
 #endif

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index bc4afec..3a9447f 100644 (file)
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -276,22 +276,22 @@ static void kvmppc_fast_vcpu_kick_hv(struct kvm_vcpu *vcpu)
  * they should never fail.)
  */
 
-static void kvmppc_core_start_stolen(struct kvmppc_vcore *vc)
+static void kvmppc_core_start_stolen(struct kvmppc_vcore *vc, u64 tb)
 {
        unsigned long flags;
 
        spin_lock_irqsave(&vc->stoltb_lock, flags);
-       vc->preempt_tb = mftb();
+       vc->preempt_tb = tb;
        spin_unlock_irqrestore(&vc->stoltb_lock, flags);
 }
 
-static void kvmppc_core_end_stolen(struct kvmppc_vcore *vc)
+static void kvmppc_core_end_stolen(struct kvmppc_vcore *vc, u64 tb)
 {
        unsigned long flags;
 
        spin_lock_irqsave(&vc->stoltb_lock, flags);
        if (vc->preempt_tb != TB_NIL) {
-               vc->stolen_tb += mftb() - vc->preempt_tb;
+               vc->stolen_tb += tb - vc->preempt_tb;
                vc->preempt_tb = TB_NIL;
        }
        spin_unlock_irqrestore(&vc->stoltb_lock, flags);
@@ -301,6 +301,7 @@ static void kvmppc_core_vcpu_load_hv(struct kvm_vcpu *vcpu, int cpu)
 {
        struct kvmppc_vcore *vc = vcpu->arch.vcore;
        unsigned long flags;
+       u64 now = mftb();
 
        /*
         * We can test vc->runner without taking the vcore lock,
@@ -309,12 +310,12 @@ static void kvmppc_core_vcpu_load_hv(struct kvm_vcpu *vcpu, int cpu)
         * ever sets it to NULL.
         */
        if (vc->runner == vcpu && vc->vcore_state >= VCORE_SLEEPING)
-               kvmppc_core_end_stolen(vc);
+               kvmppc_core_end_stolen(vc, now);
 
        spin_lock_irqsave(&vcpu->arch.tbacct_lock, flags);
        if (vcpu->arch.state == KVMPPC_VCPU_BUSY_IN_HOST &&
            vcpu->arch.busy_preempt != TB_NIL) {
-               vcpu->arch.busy_stolen += mftb() - vcpu->arch.busy_preempt;
+               vcpu->arch.busy_stolen += now - vcpu->arch.busy_preempt;
                vcpu->arch.busy_preempt = TB_NIL;
        }
        spin_unlock_irqrestore(&vcpu->arch.tbacct_lock, flags);
@@ -324,13 +325,14 @@ static void kvmppc_core_vcpu_put_hv(struct kvm_vcpu *vcpu)
 {
        struct kvmppc_vcore *vc = vcpu->arch.vcore;
        unsigned long flags;
+       u64 now = mftb();
 
        if (vc->runner == vcpu && vc->vcore_state >= VCORE_SLEEPING)
-               kvmppc_core_start_stolen(vc);
+               kvmppc_core_start_stolen(vc, now);
 
        spin_lock_irqsave(&vcpu->arch.tbacct_lock, flags);
        if (vcpu->arch.state == KVMPPC_VCPU_BUSY_IN_HOST)
-               vcpu->arch.busy_preempt = mftb();
+               vcpu->arch.busy_preempt = now;
        spin_unlock_irqrestore(&vcpu->arch.tbacct_lock, flags);
 }
 
@@ -685,7 +687,7 @@ static u64 vcore_stolen_time(struct kvmppc_vcore *vc, u64 now)
 }
 
 static void kvmppc_create_dtl_entry(struct kvm_vcpu *vcpu,
-                                   struct kvmppc_vcore *vc)
+                                   struct kvmppc_vcore *vc, u64 tb)
 {
        struct dtl_entry *dt;
        struct lppaca *vpa;
@@ -696,7 +698,7 @@ static void kvmppc_create_dtl_entry(struct kvm_vcpu *vcpu,
 
        dt = vcpu->arch.dtl_ptr;
        vpa = vcpu->arch.vpa.pinned_addr;
-       now = mftb();
+       now = tb;
        core_stolen = vcore_stolen_time(vc, now);
        stolen = core_stolen - vcpu->arch.stolen_logged;
        vcpu->arch.stolen_logged = core_stolen;
@@ -2914,14 +2916,14 @@ static void kvmppc_set_timer(struct kvm_vcpu *vcpu)
 extern int __kvmppc_vcore_entry(void);
 
 static void kvmppc_remove_runnable(struct kvmppc_vcore *vc,
-                                  struct kvm_vcpu *vcpu)
+                                  struct kvm_vcpu *vcpu, u64 tb)
 {
        u64 now;
 
        if (vcpu->arch.state != KVMPPC_VCPU_RUNNABLE)
                return;
        spin_lock_irq(&vcpu->arch.tbacct_lock);
-       now = mftb();
+       now = tb;
        vcpu->arch.busy_stolen += vcore_stolen_time(vc, now) -
                vcpu->arch.stolen_logged;
        vcpu->arch.busy_preempt = now;
@@ -3172,14 +3174,14 @@ static void kvmppc_vcore_preempt(struct kvmppc_vcore *vc)
        }
 
        /* Start accumulating stolen time */
-       kvmppc_core_start_stolen(vc);
+       kvmppc_core_start_stolen(vc, mftb());
 }
 
 static void kvmppc_vcore_end_preempt(struct kvmppc_vcore *vc)
 {
        struct preempted_vcore_list *lp;
 
-       kvmppc_core_end_stolen(vc);
+       kvmppc_core_end_stolen(vc, mftb());
        if (!list_empty(&vc->preempt_list)) {
                lp = &per_cpu(preempted_vcores, vc->pcpu);
                spin_lock(&lp->lock);
@@ -3306,7 +3308,7 @@ static void prepare_threads(struct kvmppc_vcore *vc)
                        vcpu->arch.ret = RESUME_GUEST;
                else
                        continue;
-               kvmppc_remove_runnable(vc, vcpu);
+               kvmppc_remove_runnable(vc, vcpu, mftb());
                wake_up(&vcpu->arch.cpu_run);
        }
 }
@@ -3325,7 +3327,7 @@ static void collect_piggybacks(struct core_info *cip, int target_threads)
                        list_del_init(&pvc->preempt_list);
                        if (pvc->runner == NULL) {
                                pvc->vcore_state = VCORE_INACTIVE;
-                               kvmppc_core_end_stolen(pvc);
+                               kvmppc_core_end_stolen(pvc, mftb());
                        }
                        spin_unlock(&pvc->lock);
                        continue;
@@ -3334,7 +3336,7 @@ static void collect_piggybacks(struct core_info *cip, int target_threads)
                        spin_unlock(&pvc->lock);
                        continue;
                }
-               kvmppc_core_end_stolen(pvc);
+               kvmppc_core_end_stolen(pvc, mftb());
                pvc->vcore_state = VCORE_PIGGYBACK;
                if (cip->total_threads >= target_threads)
                        break;
@@ -3401,7 +3403,7 @@ static void post_guest_process(struct kvmppc_vcore *vc, bool is_master)
                        else
                                ++still_running;
                } else {
-                       kvmppc_remove_runnable(vc, vcpu);
+                       kvmppc_remove_runnable(vc, vcpu, mftb());
                        wake_up(&vcpu->arch.cpu_run);
                }
        }
@@ -3410,7 +3412,7 @@ static void post_guest_process(struct kvmppc_vcore *vc, bool is_master)
                        kvmppc_vcore_preempt(vc);
                } else if (vc->runner) {
                        vc->vcore_state = VCORE_PREEMPT;
-                       kvmppc_core_start_stolen(vc);
+                       kvmppc_core_start_stolen(vc, mftb());
                } else {
                        vc->vcore_state = VCORE_INACTIVE;
                }
@@ -3541,7 +3543,7 @@ static noinline void kvmppc_run_core(struct kvmppc_vcore *vc)
            ((vc->num_threads > threads_per_subcore) || !on_primary_thread())) {
                for_each_runnable_thread(i, vcpu, vc) {
                        vcpu->arch.ret = -EBUSY;
-                       kvmppc_remove_runnable(vc, vcpu);
+                       kvmppc_remove_runnable(vc, vcpu, mftb());
                        wake_up(&vcpu->arch.cpu_run);
                }
                goto out;
@@ -3673,7 +3675,7 @@ static noinline void kvmppc_run_core(struct kvmppc_vcore *vc)
                pvc->pcpu = pcpu + thr;
                for_each_runnable_thread(i, vcpu, pvc) {
                        kvmppc_start_thread(vcpu, pvc);
-                       kvmppc_create_dtl_entry(vcpu, pvc);
+                       kvmppc_create_dtl_entry(vcpu, pvc, mftb());
                        trace_kvm_guest_enter(vcpu);
                        if (!vcpu->arch.ptid)
                                thr0_done = true;
@@ -4152,20 +4154,17 @@ static void vcpu_vpa_increment_dispatch(struct kvm_vcpu *vcpu)
  * Guest entry for POWER9 and later CPUs.
  */
 static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
-                        unsigned long lpcr)
+                        unsigned long lpcr, u64 *tb)
 {
        struct kvmppc_vcore *vc = vcpu->arch.vcore;
        struct p9_host_os_sprs host_os_sprs;
        s64 dec;
-       u64 tb, next_timer;
+       u64 next_timer;
        unsigned long msr;
        int trap;
 
-       WARN_ON_ONCE(vcpu->arch.ceded);
-
-       tb = mftb();
        next_timer = timer_get_next_tb();
-       if (tb >= next_timer)
+       if (*tb >= next_timer)
                return BOOK3S_INTERRUPT_HV_DECREMENTER;
        if (next_timer < time_limit)
                time_limit = next_timer;
@@ -4262,7 +4261,7 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
                 *
                 * XXX: Another day's problem.
                 */
-               mtspr(SPRN_DEC, kvmppc_dec_expires_host_tb(vcpu) - tb);
+               mtspr(SPRN_DEC, kvmppc_dec_expires_host_tb(vcpu) - *tb);
 
                mtspr(SPRN_DAR, vcpu->arch.shregs.dar);
                mtspr(SPRN_DSISR, vcpu->arch.shregs.dsisr);
@@ -4278,8 +4277,8 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
                dec = mfspr(SPRN_DEC);
                if (!(lpcr & LPCR_LD)) /* Sign extend if not using large decrementer */
                        dec = (s32) dec;
-               tb = mftb();
-               vcpu->arch.dec_expires = dec + (tb + vc->tb_offset);
+               *tb = mftb();
+               vcpu->arch.dec_expires = dec + (*tb + vc->tb_offset);
 
                /* H_CEDE has to be handled now, not later */
                if (trap == BOOK3S_INTERRUPT_SYSCALL && !vcpu->arch.nested &&
@@ -4291,7 +4290,7 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
 
        } else {
                kvmppc_xive_push_vcpu(vcpu);
-               trap = kvmhv_vcpu_entry_p9(vcpu, time_limit, lpcr);
+               trap = kvmhv_vcpu_entry_p9(vcpu, time_limit, lpcr, tb);
                if (trap == BOOK3S_INTERRUPT_SYSCALL && !vcpu->arch.nested &&
                    !(vcpu->arch.shregs.msr & MSR_PR)) {
                        unsigned long req = kvmppc_get_gpr(vcpu, 3);
@@ -4322,6 +4321,8 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
 
        store_spr_state(vcpu);
 
+       timer_rearm_host_dec(*tb);
+
        restore_p9_host_os_sprs(vcpu, &host_os_sprs);
 
        store_fp_state(&vcpu->arch.fp);
@@ -4341,8 +4342,6 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
        vc->entry_exit_map = 0x101;
        vc->in_guest = 0;
 
-       timer_rearm_host_dec(tb);
-
        kvmppc_subcore_exit_guest();
 
        return trap;
@@ -4596,7 +4595,7 @@ static int kvmppc_run_vcpu(struct kvm_vcpu *vcpu)
                if ((vc->vcore_state == VCORE_PIGGYBACK ||
                     vc->vcore_state == VCORE_RUNNING) &&
                           !VCORE_IS_EXITING(vc)) {
-                       kvmppc_create_dtl_entry(vcpu, vc);
+                       kvmppc_create_dtl_entry(vcpu, vc, mftb());
                        kvmppc_start_thread(vcpu, vc);
                        trace_kvm_guest_enter(vcpu);
                } else if (vc->vcore_state == VCORE_SLEEPING) {
@@ -4631,7 +4630,7 @@ static int kvmppc_run_vcpu(struct kvm_vcpu *vcpu)
                for_each_runnable_thread(i, v, vc) {
                        kvmppc_core_prepare_to_enter(v);
                        if (signal_pending(v->arch.run_task)) {
-                               kvmppc_remove_runnable(vc, v);
+                               kvmppc_remove_runnable(vc, v, mftb());
                                v->stat.signal_exits++;
                                v->run->exit_reason = KVM_EXIT_INTR;
                                v->arch.ret = -EINTR;
@@ -4672,7 +4671,7 @@ static int kvmppc_run_vcpu(struct kvm_vcpu *vcpu)
                kvmppc_vcore_end_preempt(vc);
 
        if (vcpu->arch.state == KVMPPC_VCPU_RUNNABLE) {
-               kvmppc_remove_runnable(vc, vcpu);
+               kvmppc_remove_runnable(vc, vcpu, mftb());
                vcpu->stat.signal_exits++;
                run->exit_reason = KVM_EXIT_INTR;
                vcpu->arch.ret = -EINTR;
@@ -4700,6 +4699,7 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, u64 time_limit,
        struct kvm *kvm = vcpu->kvm;
        struct kvm_nested_guest *nested = vcpu->arch.nested;
        unsigned long flags;
+       u64 tb;
 
        trace_kvmppc_run_vcpu_enter(vcpu);
 
@@ -4710,7 +4710,6 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, u64 time_limit,
        vc = vcpu->arch.vcore;
        vcpu->arch.ceded = 0;
        vcpu->arch.run_task = current;
-       vcpu->arch.stolen_logged = vcore_stolen_time(vc, mftb());
        vcpu->arch.state = KVMPPC_VCPU_RUNNABLE;
        vcpu->arch.busy_preempt = TB_NIL;
        vcpu->arch.last_inst = KVM_INST_FETCH_FAILED;
@@ -4735,7 +4734,6 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, u64 time_limit,
        kvmppc_update_vpas(vcpu);
 
        init_vcore_to_run(vc);
-       vc->preempt_tb = TB_NIL;
 
        preempt_disable();
        pcpu = smp_processor_id();
@@ -4745,6 +4743,7 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, u64 time_limit,
 
        /* flags save not required, but irq_pmu has no disable/enable API */
        powerpc_local_irq_pmu_save(flags);
+
        if (signal_pending(current))
                goto sigpend;
        if (need_resched() || !kvm->arch.mmu_ready)
@@ -4767,12 +4766,17 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, u64 time_limit,
                goto out;
        }
 
+       tb = mftb();
+
+       vcpu->arch.stolen_logged = vcore_stolen_time(vc, tb);
+       vc->preempt_tb = TB_NIL;
+
        kvmppc_clear_host_core(pcpu);
 
        local_paca->kvm_hstate.napping = 0;
        local_paca->kvm_hstate.kvm_split_mode = NULL;
        kvmppc_start_thread(vcpu, vc);
-       kvmppc_create_dtl_entry(vcpu, vc);
+       kvmppc_create_dtl_entry(vcpu, vc, tb);
        trace_kvm_guest_enter(vcpu);
 
        vc->vcore_state = VCORE_RUNNING;
@@ -4787,7 +4791,7 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, u64 time_limit,
        /* Tell lockdep that we're about to enable interrupts */
        trace_hardirqs_on();
 
-       trap = kvmhv_p9_guest_entry(vcpu, time_limit, lpcr);
+       trap = kvmhv_p9_guest_entry(vcpu, time_limit, lpcr, &tb);
        vcpu->arch.trap = trap;
 
        trace_hardirqs_off();
@@ -4829,7 +4833,7 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, u64 time_limit,
         * by L2 and the L1 decrementer is provided in hdec_expires
         */
        if (kvmppc_core_pending_dec(vcpu) &&
-                       ((get_tb() < kvmppc_dec_expires_host_tb(vcpu)) ||
+                       ((tb < kvmppc_dec_expires_host_tb(vcpu)) ||
                         (trap == BOOK3S_INTERRUPT_SYSCALL &&
                          kvmppc_get_gpr(vcpu, 3) == H_ENTER_NESTED)))
                kvmppc_core_dequeue_dec(vcpu);
@@ -4865,7 +4869,7 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, u64 time_limit,
        trace_kvmppc_run_core(vc, 1);
 
  done:
-       kvmppc_remove_runnable(vc, vcpu);
+       kvmppc_remove_runnable(vc, vcpu, tb);
        trace_kvmppc_run_vcpu_exit(vcpu);
 
        return vcpu->arch.ret;

diff --git a/arch/powerpc/kvm/book3s_hv_p9_entry.c b/arch/powerpc/kvm/book3s_hv_p9_entry.c
index e7793bb..2bd96d8 100644 (file)
--- a/arch/powerpc/kvm/book3s_hv_p9_entry.c
+++ b/arch/powerpc/kvm/book3s_hv_p9_entry.c
@@ -183,13 +183,13 @@ static void save_clear_guest_mmu(struct kvm *kvm, struct kvm_vcpu *vcpu)
        }
 }
 
-int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpcr)
+int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpcr, u64 *tb)
 {
        struct kvm *kvm = vcpu->kvm;
        struct kvm_nested_guest *nested = vcpu->arch.nested;
        struct kvmppc_vcore *vc = vcpu->arch.vcore;
        s64 hdec, dec;
-       u64 tb, purr, spurr;
+       u64 purr, spurr;
        u64 *exsave;
        bool ri_set;
        int trap;
@@ -203,8 +203,7 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc
        unsigned long host_dawr1;
        unsigned long host_dawrx1;
 
-       tb = mftb();
-       hdec = time_limit - tb;
+       hdec = time_limit - *tb;
        if (hdec < 0)
                return BOOK3S_INTERRUPT_HV_DECREMENTER;
 
@@ -230,11 +229,13 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc
        }
 
        if (vc->tb_offset) {
-               u64 new_tb = tb + vc->tb_offset;
+               u64 new_tb = *tb + vc->tb_offset;
                mtspr(SPRN_TBU40, new_tb);
-               tb = mftb();
-               if ((tb & 0xffffff) < (new_tb & 0xffffff))
-                       mtspr(SPRN_TBU40, new_tb + 0x1000000);
+               if ((mftb() & 0xffffff) < (new_tb & 0xffffff)) {
+                       new_tb += 0x1000000;
+                       mtspr(SPRN_TBU40, new_tb);
+               }
+               *tb = new_tb;
                vc->tb_offset_applied = vc->tb_offset;
        }
 
@@ -317,7 +318,7 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc
         */
        mtspr(SPRN_HDEC, hdec);
 
-       mtspr(SPRN_DEC, vcpu->arch.dec_expires - tb);
+       mtspr(SPRN_DEC, vcpu->arch.dec_expires - *tb);
 
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 tm_return_to_guest:
@@ -466,15 +467,17 @@ tm_return_to_guest:
        dec = mfspr(SPRN_DEC);
        if (!(lpcr & LPCR_LD)) /* Sign extend if not using large decrementer */
                dec = (s32) dec;
-       tb = mftb();
-       vcpu->arch.dec_expires = dec + tb;
+       *tb = mftb();
+       vcpu->arch.dec_expires = dec + *tb;
 
        if (vc->tb_offset_applied) {
-               u64 new_tb = tb - vc->tb_offset_applied;
+               u64 new_tb = *tb - vc->tb_offset_applied;
                mtspr(SPRN_TBU40, new_tb);
-               tb = mftb();
-               if ((tb & 0xffffff) < (new_tb & 0xffffff))
-                       mtspr(SPRN_TBU40, new_tb + 0x1000000);
+               if ((mftb() & 0xffffff) < (new_tb & 0xffffff)) {
+                       new_tb += 0x1000000;
+                       mtspr(SPRN_TBU40, new_tb);
+               }
+               *tb = new_tb;
                vc->tb_offset_applied = 0;
        }