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Commit 8ad35755 authored by David Hildenbrand's avatar David Hildenbrand Committed by Christian Borntraeger
Browse files

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: default avatarDavid Hildenbrand <dahi@linux.vnet.ibm.com>
Reviewed-by: default avatarDominik Dingel <dingel@linux.vnet.ibm.com>
Reviewed-by: default avatarCornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
parent 6852d7b6

arch/s390/include/asm/kvm_host.h

+2 −0
Original line number Diff line number Diff line
@@ -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)

arch/s390/kvm/kvm-s390.c

+121 −2
Original line number Diff line number Diff line
@@ -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,

arch/s390/kvm/trace-s390.h

+22 −0
Original line number Diff line number Diff line
@@ -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 */

include/linux/kvm_host.h

+2 −0
Original line number Diff line number Diff line
@@ -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