KVM: s390: enable IBS for single running VCPUs

This patch enables the IBS facility when a single VCPU is running.
The facility is dynamically turned on/off as soon as other VCPUs
enter/leave the stopped state.

When this facility is operating, some instructions can be executed
faster for single-cpu guests.

Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Reviewed-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
This commit is contained in:
David Hildenbrand 2014-03-14 11:00:21 +01:00 коммит произвёл Christian Borntraeger
Родитель 6852d7b69b
Коммит 8ad3575517
4 изменённых файлов: 147 добавлений и 2 удалений

Просмотреть файл

@ -72,6 +72,7 @@ struct sca_block {
#define CPUSTAT_ZARCH 0x00000800
#define CPUSTAT_MCDS 0x00000100
#define CPUSTAT_SM 0x00000080
#define CPUSTAT_IBS 0x00000040
#define CPUSTAT_G 0x00000008
#define CPUSTAT_GED 0x00000004
#define CPUSTAT_J 0x00000002
@ -411,6 +412,7 @@ struct kvm_arch{
int use_cmma;
struct s390_io_adapter *adapters[MAX_S390_IO_ADAPTERS];
wait_queue_head_t ipte_wq;
spinlock_t start_stop_lock;
};
#define KVM_HVA_ERR_BAD (-1UL)

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@ -458,6 +458,8 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
kvm->arch.css_support = 0;
kvm->arch.use_irqchip = 0;
spin_lock_init(&kvm->arch.start_stop_lock);
return 0;
out_nogmap:
debug_unregister(kvm->arch.dbf);
@ -996,8 +998,15 @@ bool kvm_s390_cmma_enabled(struct kvm *kvm)
return true;
}
static bool ibs_enabled(struct kvm_vcpu *vcpu)
{
return atomic_read(&vcpu->arch.sie_block->cpuflags) & CPUSTAT_IBS;
}
static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu)
{
retry:
s390_vcpu_unblock(vcpu);
/*
* We use MMU_RELOAD just to re-arm the ipte notifier for the
* guest prefix page. gmap_ipte_notify will wait on the ptl lock.
@ -1005,15 +1014,34 @@ static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu)
* already finished. We might race against a second unmapper that
* wants to set the blocking bit. Lets just retry the request loop.
*/
while (kvm_check_request(KVM_REQ_MMU_RELOAD, vcpu)) {
if (kvm_check_request(KVM_REQ_MMU_RELOAD, vcpu)) {
int rc;
rc = gmap_ipte_notify(vcpu->arch.gmap,
vcpu->arch.sie_block->prefix,
PAGE_SIZE * 2);
if (rc)
return rc;
s390_vcpu_unblock(vcpu);
goto retry;
}
if (kvm_check_request(KVM_REQ_ENABLE_IBS, vcpu)) {
if (!ibs_enabled(vcpu)) {
trace_kvm_s390_enable_disable_ibs(vcpu->vcpu_id, 1);
atomic_set_mask(CPUSTAT_IBS,
&vcpu->arch.sie_block->cpuflags);
}
goto retry;
}
if (kvm_check_request(KVM_REQ_DISABLE_IBS, vcpu)) {
if (ibs_enabled(vcpu)) {
trace_kvm_s390_enable_disable_ibs(vcpu->vcpu_id, 0);
atomic_clear_mask(CPUSTAT_IBS,
&vcpu->arch.sie_block->cpuflags);
}
goto retry;
}
return 0;
}
@ -1362,16 +1390,107 @@ int kvm_s390_vcpu_store_status(struct kvm_vcpu *vcpu, unsigned long addr)
return kvm_s390_store_status_unloaded(vcpu, addr);
}
static inline int is_vcpu_stopped(struct kvm_vcpu *vcpu)
{
return atomic_read(&(vcpu)->arch.sie_block->cpuflags) & CPUSTAT_STOPPED;
}
static void __disable_ibs_on_vcpu(struct kvm_vcpu *vcpu)
{
kvm_check_request(KVM_REQ_ENABLE_IBS, vcpu);
kvm_make_request(KVM_REQ_DISABLE_IBS, vcpu);
exit_sie_sync(vcpu);
}
static void __disable_ibs_on_all_vcpus(struct kvm *kvm)
{
unsigned int i;
struct kvm_vcpu *vcpu;
kvm_for_each_vcpu(i, vcpu, kvm) {
__disable_ibs_on_vcpu(vcpu);
}
}
static void __enable_ibs_on_vcpu(struct kvm_vcpu *vcpu)
{
kvm_check_request(KVM_REQ_DISABLE_IBS, vcpu);
kvm_make_request(KVM_REQ_ENABLE_IBS, vcpu);
exit_sie_sync(vcpu);
}
void kvm_s390_vcpu_start(struct kvm_vcpu *vcpu)
{
int i, online_vcpus, started_vcpus = 0;
if (!is_vcpu_stopped(vcpu))
return;
trace_kvm_s390_vcpu_start_stop(vcpu->vcpu_id, 1);
/* Only one cpu at a time may enter/leave the STOPPED state. */
spin_lock_bh(&vcpu->kvm->arch.start_stop_lock);
online_vcpus = atomic_read(&vcpu->kvm->online_vcpus);
for (i = 0; i < online_vcpus; i++) {
if (!is_vcpu_stopped(vcpu->kvm->vcpus[i]))
started_vcpus++;
}
if (started_vcpus == 0) {
/* we're the only active VCPU -> speed it up */
__enable_ibs_on_vcpu(vcpu);
} else if (started_vcpus == 1) {
/*
* As we are starting a second VCPU, we have to disable
* the IBS facility on all VCPUs to remove potentially
* oustanding ENABLE requests.
*/
__disable_ibs_on_all_vcpus(vcpu->kvm);
}
atomic_clear_mask(CPUSTAT_STOPPED, &vcpu->arch.sie_block->cpuflags);
/*
* Another VCPU might have used IBS while we were offline.
* Let's play safe and flush the VCPU at startup.
*/
vcpu->arch.sie_block->ihcpu = 0xffff;
spin_unlock_bh(&vcpu->kvm->arch.start_stop_lock);
return;
}
void kvm_s390_vcpu_stop(struct kvm_vcpu *vcpu)
{
int i, online_vcpus, started_vcpus = 0;
struct kvm_vcpu *started_vcpu = NULL;
if (is_vcpu_stopped(vcpu))
return;
trace_kvm_s390_vcpu_start_stop(vcpu->vcpu_id, 0);
/* Only one cpu at a time may enter/leave the STOPPED state. */
spin_lock_bh(&vcpu->kvm->arch.start_stop_lock);
online_vcpus = atomic_read(&vcpu->kvm->online_vcpus);
atomic_set_mask(CPUSTAT_STOPPED, &vcpu->arch.sie_block->cpuflags);
__disable_ibs_on_vcpu(vcpu);
for (i = 0; i < online_vcpus; i++) {
if (!is_vcpu_stopped(vcpu->kvm->vcpus[i])) {
started_vcpus++;
started_vcpu = vcpu->kvm->vcpus[i];
}
}
if (started_vcpus == 1) {
/*
* As we only have one VCPU left, we want to enable the
* IBS facility for that VCPU to speed it up.
*/
__enable_ibs_on_vcpu(started_vcpu);
}
spin_unlock_bh(&vcpu->kvm->arch.start_stop_lock);
return;
}
static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,

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@ -244,6 +244,28 @@ TRACE_EVENT(kvm_s390_enable_css,
__entry->kvm)
);
/*
* Trace point for enabling and disabling interlocking-and-broadcasting
* suppression.
*/
TRACE_EVENT(kvm_s390_enable_disable_ibs,
TP_PROTO(unsigned int id, int state),
TP_ARGS(id, state),
TP_STRUCT__entry(
__field(unsigned int, id)
__field(int, state)
),
TP_fast_assign(
__entry->id = id;
__entry->state = state;
),
TP_printk("%s ibs on cpu %d",
__entry->state ? "enabling" : "disabling", __entry->id)
);
#endif /* _TRACE_KVMS390_H */

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@ -134,6 +134,8 @@ static inline bool is_error_page(struct page *page)
#define KVM_REQ_EPR_EXIT 20
#define KVM_REQ_SCAN_IOAPIC 21
#define KVM_REQ_GLOBAL_CLOCK_UPDATE 22
#define KVM_REQ_ENABLE_IBS 23
#define KVM_REQ_DISABLE_IBS 24
#define KVM_USERSPACE_IRQ_SOURCE_ID 0
#define KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID 1