[PATCH 1/4] kvm/ppc/book3s_hv: Change vcore element runnable_threads from linked-list to array
Suraj Jitindar Singh
sjitindarsingh at gmail.com
Wed Jun 15 19:21:05 AEST 2016
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 <sjitindarsingh at gmail.com>
---
arch/powerpc/include/asm/kvm_host.h | 3 +-
arch/powerpc/kvm/book3s_hv.c | 68 +++++++++++++++++++++++--------------
2 files changed, 43 insertions(+), 28 deletions(-)
diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index ec35af3..4915443 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -293,7 +293,7 @@ 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;
@@ -668,7 +668,6 @@ 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 e20beae..3bcf9e6 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -57,6 +57,7 @@
#include <linux/highmem.h>
#include <linux/hugetlb.h>
#include <linux/module.h>
+#include <linux/compiler.h>
#include "book3s.h"
@@ -96,6 +97,26 @@ 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 */
@@ -1492,7 +1513,6 @@ 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);
@@ -1801,7 +1821,7 @@ 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)
@@ -2208,10 +2228,10 @@ 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 ||
@@ -2258,15 +2278,14 @@ 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))
@@ -2306,8 +2325,8 @@ 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);
}
}
@@ -2360,7 +2379,7 @@ 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;
@@ -2396,8 +2415,7 @@ 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);
@@ -2476,8 +2494,7 @@ 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);
@@ -2610,7 +2627,7 @@ 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);
@@ -2619,7 +2636,7 @@ 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;
@@ -2643,9 +2660,9 @@ 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);
@@ -2665,7 +2682,7 @@ 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;
/*
@@ -2705,8 +2722,7 @@ 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);
@@ -2719,7 +2735,7 @@ 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
@@ -2758,8 +2774,8 @@ 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);
}
--
2.5.5
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