From 7b5f8272c792d49da73d98e9ca32f4cbb6d53808 Mon Sep 17 00:00:00 2001 From: Suraj Jitindar Singh Date: Tue, 2 Aug 2016 14:03:20 +1000 Subject: [PATCH] KVM: PPC: Book3S HV: Change vcore element runnable_threads from linked-list to array The struct kvmppc_vcore is a structure used to store various information about a virtual core for a kvm guest. The runnable_threads element of the struct provides a list of all of the currently runnable vcpus on the core (those in the KVMPPC_VCPU_RUNNABLE state). The previous implementation of this list was a linked_list. The next patch requires that the list be able to be iterated over without holding the vcore lock. Reimplement the runnable_threads list in the kvmppc_vcore struct as an array. Implement function to iterate over valid entries in the array and update access sites accordingly. Signed-off-by: Suraj Jitindar Singh Signed-off-by: Paul Mackerras --- arch/powerpc/include/asm/kvm_book3s.h | 2 +- arch/powerpc/include/asm/kvm_host.h | 1 - arch/powerpc/kvm/book3s_hv.c | 68 +++++++++++++++++---------- 3 files changed, 43 insertions(+), 28 deletions(-) diff --git a/arch/powerpc/include/asm/kvm_book3s.h b/arch/powerpc/include/asm/kvm_book3s.h index a50c5fec9790..151f8173e596 100644 --- a/arch/powerpc/include/asm/kvm_book3s.h +++ b/arch/powerpc/include/asm/kvm_book3s.h @@ -87,7 +87,7 @@ struct kvmppc_vcore { u8 vcore_state; u8 in_guest; struct kvmppc_vcore *master_vcore; - struct list_head runnable_threads; + struct kvm_vcpu *runnable_threads[MAX_SMT_THREADS]; struct list_head preempt_list; spinlock_t lock; struct swait_queue_head wq; diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h index 7ff9919916c3..851575a0c328 100644 --- a/arch/powerpc/include/asm/kvm_host.h +++ b/arch/powerpc/include/asm/kvm_host.h @@ -635,7 +635,6 @@ struct kvm_vcpu_arch { long pgfault_index; unsigned long pgfault_hpte[2]; - struct list_head run_list; struct task_struct *run_task; struct kvm_run *kvm_run; diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index 2fd5580c8f6e..ebbab1b2206c 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -58,6 +58,7 @@ #include #include #include +#include #include "book3s.h" @@ -97,6 +98,26 @@ MODULE_PARM_DESC(h_ipi_redirect, "Redirect H_IPI wakeup to a free host core"); static void kvmppc_end_cede(struct kvm_vcpu *vcpu); static int kvmppc_hv_setup_htab_rma(struct kvm_vcpu *vcpu); +static inline struct kvm_vcpu *next_runnable_thread(struct kvmppc_vcore *vc, + int *ip) +{ + int i = *ip; + struct kvm_vcpu *vcpu; + + while (++i < MAX_SMT_THREADS) { + vcpu = READ_ONCE(vc->runnable_threads[i]); + if (vcpu) { + *ip = i; + return vcpu; + } + } + return NULL; +} + +/* Used to traverse the list of runnable threads for a given vcore */ +#define for_each_runnable_thread(i, vcpu, vc) \ + for (i = -1; (vcpu = next_runnable_thread(vc, &i)); ) + static bool kvmppc_ipi_thread(int cpu) { /* On POWER8 for IPIs to threads in the same core, use msgsnd */ @@ -1493,7 +1514,6 @@ static struct kvmppc_vcore *kvmppc_vcore_create(struct kvm *kvm, int core) if (vcore == NULL) return NULL; - INIT_LIST_HEAD(&vcore->runnable_threads); spin_lock_init(&vcore->lock); spin_lock_init(&vcore->stoltb_lock); init_swait_queue_head(&vcore->wq); @@ -1802,7 +1822,7 @@ static void kvmppc_remove_runnable(struct kvmppc_vcore *vc, vcpu->arch.state = KVMPPC_VCPU_BUSY_IN_HOST; spin_unlock_irq(&vcpu->arch.tbacct_lock); --vc->n_runnable; - list_del(&vcpu->arch.run_list); + WRITE_ONCE(vc->runnable_threads[vcpu->arch.ptid], NULL); } static int kvmppc_grab_hwthread(int cpu) @@ -2209,10 +2229,10 @@ static bool can_piggyback(struct kvmppc_vcore *pvc, struct core_info *cip, static void prepare_threads(struct kvmppc_vcore *vc) { - struct kvm_vcpu *vcpu, *vnext; + int i; + struct kvm_vcpu *vcpu; - list_for_each_entry_safe(vcpu, vnext, &vc->runnable_threads, - arch.run_list) { + for_each_runnable_thread(i, vcpu, vc) { if (signal_pending(vcpu->arch.run_task)) vcpu->arch.ret = -EINTR; else if (vcpu->arch.vpa.update_pending || @@ -2259,15 +2279,14 @@ static void collect_piggybacks(struct core_info *cip, int target_threads) static void post_guest_process(struct kvmppc_vcore *vc, bool is_master) { - int still_running = 0; + int still_running = 0, i; u64 now; long ret; - struct kvm_vcpu *vcpu, *vnext; + struct kvm_vcpu *vcpu; spin_lock(&vc->lock); now = get_tb(); - list_for_each_entry_safe(vcpu, vnext, &vc->runnable_threads, - arch.run_list) { + for_each_runnable_thread(i, vcpu, vc) { /* cancel pending dec exception if dec is positive */ if (now < vcpu->arch.dec_expires && kvmppc_core_pending_dec(vcpu)) @@ -2307,8 +2326,8 @@ static void post_guest_process(struct kvmppc_vcore *vc, bool is_master) } if (vc->n_runnable > 0 && vc->runner == NULL) { /* make sure there's a candidate runner awake */ - vcpu = list_first_entry(&vc->runnable_threads, - struct kvm_vcpu, arch.run_list); + i = -1; + vcpu = next_runnable_thread(vc, &i); wake_up(&vcpu->arch.cpu_run); } } @@ -2361,7 +2380,7 @@ static inline void kvmppc_set_host_core(int cpu) */ static noinline void kvmppc_run_core(struct kvmppc_vcore *vc) { - struct kvm_vcpu *vcpu, *vnext; + struct kvm_vcpu *vcpu; int i; int srcu_idx; struct core_info core_info; @@ -2397,8 +2416,7 @@ static noinline void kvmppc_run_core(struct kvmppc_vcore *vc) */ if ((threads_per_core > 1) && ((vc->num_threads > threads_per_subcore) || !on_primary_thread())) { - list_for_each_entry_safe(vcpu, vnext, &vc->runnable_threads, - arch.run_list) { + for_each_runnable_thread(i, vcpu, vc) { vcpu->arch.ret = -EBUSY; kvmppc_remove_runnable(vc, vcpu); wake_up(&vcpu->arch.cpu_run); @@ -2477,8 +2495,7 @@ static noinline void kvmppc_run_core(struct kvmppc_vcore *vc) active |= 1 << thr; list_for_each_entry(pvc, &core_info.vcs[sub], preempt_list) { pvc->pcpu = pcpu + thr; - list_for_each_entry(vcpu, &pvc->runnable_threads, - arch.run_list) { + for_each_runnable_thread(i, vcpu, pvc) { kvmppc_start_thread(vcpu, pvc); kvmppc_create_dtl_entry(vcpu, pvc); trace_kvm_guest_enter(vcpu); @@ -2611,7 +2628,7 @@ static void kvmppc_wait_for_exec(struct kvmppc_vcore *vc, static void kvmppc_vcore_blocked(struct kvmppc_vcore *vc) { struct kvm_vcpu *vcpu; - int do_sleep = 1; + int do_sleep = 1, i; DECLARE_SWAITQUEUE(wait); prepare_to_swait(&vc->wq, &wait, TASK_INTERRUPTIBLE); @@ -2620,7 +2637,7 @@ static void kvmppc_vcore_blocked(struct kvmppc_vcore *vc) * Check one last time for pending exceptions and ceded state after * we put ourselves on the wait queue */ - list_for_each_entry(vcpu, &vc->runnable_threads, arch.run_list) { + for_each_runnable_thread(i, vcpu, vc) { if (vcpu->arch.pending_exceptions || !vcpu->arch.ceded) { do_sleep = 0; break; @@ -2644,9 +2661,9 @@ static void kvmppc_vcore_blocked(struct kvmppc_vcore *vc) static int kvmppc_run_vcpu(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu) { - int n_ceded; + int n_ceded, i; struct kvmppc_vcore *vc; - struct kvm_vcpu *v, *vn; + struct kvm_vcpu *v; trace_kvmppc_run_vcpu_enter(vcpu); @@ -2666,7 +2683,7 @@ static int kvmppc_run_vcpu(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu) vcpu->arch.stolen_logged = vcore_stolen_time(vc, mftb()); vcpu->arch.state = KVMPPC_VCPU_RUNNABLE; vcpu->arch.busy_preempt = TB_NIL; - list_add_tail(&vcpu->arch.run_list, &vc->runnable_threads); + WRITE_ONCE(vc->runnable_threads[vcpu->arch.ptid], vcpu); ++vc->n_runnable; /* @@ -2706,8 +2723,7 @@ static int kvmppc_run_vcpu(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu) kvmppc_wait_for_exec(vc, vcpu, TASK_INTERRUPTIBLE); continue; } - list_for_each_entry_safe(v, vn, &vc->runnable_threads, - arch.run_list) { + 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); @@ -2720,7 +2736,7 @@ static int kvmppc_run_vcpu(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu) if (!vc->n_runnable || vcpu->arch.state != KVMPPC_VCPU_RUNNABLE) break; n_ceded = 0; - list_for_each_entry(v, &vc->runnable_threads, arch.run_list) { + for_each_runnable_thread(i, v, vc) { if (!v->arch.pending_exceptions) n_ceded += v->arch.ceded; else @@ -2759,8 +2775,8 @@ static int kvmppc_run_vcpu(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu) if (vc->n_runnable && vc->vcore_state == VCORE_INACTIVE) { /* Wake up some vcpu to run the core */ - v = list_first_entry(&vc->runnable_threads, - struct kvm_vcpu, arch.run_list); + i = -1; + v = next_runnable_thread(vc, &i); wake_up(&v->arch.cpu_run); } -- 2.20.1