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Commit 41628d33 authored by Konstantin Weitz's avatar Konstantin Weitz Committed by Marcelo Tosatti
Browse files

KVM: s390: Implement the directed yield (diag 9c) hypervisor call for KVM 



This patch implements the directed yield hypercall found on other
System z hypervisors. It delegates execution time to the virtual cpu
specified in the instruction's parameter.

Useful to avoid long spinlock waits in the guest.

Christian Borntraeger: moved common code in virt/kvm/

Signed-off-by: default avatarKonstantin Weitz <WEITZKON@de.ibm.com>
Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent b6ddf05f

arch/s390/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -148,6 +148,7 @@ struct kvm_vcpu_stat { 
	u32 instruction_sigp_restart;

	u32 diagnose_10;

	u32 diagnose_44;

	u32 diagnose_9c;

};



struct kvm_s390_io_info {

arch/s390/kvm/diag.c

+25 −0
Original line number Diff line number Diff line
@@ -53,6 +53,29 @@ static int __diag_time_slice_end(struct kvm_vcpu *vcpu) 
	return 0;

}



static int __diag_time_slice_end_directed(struct kvm_vcpu *vcpu)

{

	struct kvm *kvm = vcpu->kvm;

	struct kvm_vcpu *tcpu;

	int tid;

	int i;



	tid = vcpu->run->s.regs.gprs[(vcpu->arch.sie_block->ipa & 0xf0) >> 4];

	vcpu->stat.diagnose_9c++;

	VCPU_EVENT(vcpu, 5, "diag time slice end directed to %d", tid);



	if (tid == vcpu->vcpu_id)

		return 0;



	kvm_for_each_vcpu(i, tcpu, kvm)

		if (tcpu->vcpu_id == tid) {

			kvm_vcpu_yield_to(tcpu);

			break;

		}



	return 0;

}



static int __diag_ipl_functions(struct kvm_vcpu *vcpu)

{

	unsigned int reg = vcpu->arch.sie_block->ipa & 0xf;
@@ -89,6 +112,8 @@ int kvm_s390_handle_diag(struct kvm_vcpu *vcpu) 
		return diag_release_pages(vcpu);

	case 0x44:

		return __diag_time_slice_end(vcpu);

	case 0x9c:

		return __diag_time_slice_end_directed(vcpu);

	case 0x308:

		return __diag_ipl_functions(vcpu);

	default:

arch/s390/kvm/kvm-s390.c

+1 −0
Original line number Diff line number Diff line
@@ -74,6 +74,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = { 
	{ "instruction_sigp_restart", VCPU_STAT(instruction_sigp_restart) },

	{ "diagnose_10", VCPU_STAT(diagnose_10) },

	{ "diagnose_44", VCPU_STAT(diagnose_44) },

	{ "diagnose_9c", VCPU_STAT(diagnose_9c) },

	{ NULL }

};

include/linux/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -461,6 +461,7 @@ void mark_page_dirty_in_slot(struct kvm *kvm, struct kvm_memory_slot *memslot, 


void kvm_vcpu_block(struct kvm_vcpu *vcpu);

void kvm_vcpu_kick(struct kvm_vcpu *vcpu);

bool kvm_vcpu_yield_to(struct kvm_vcpu *target);

void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu);

void kvm_resched(struct kvm_vcpu *vcpu);

void kvm_load_guest_fpu(struct kvm_vcpu *vcpu);

virt/kvm/kvm_main.c

+26 −16
Original line number Diff line number Diff line
@@ -1543,6 +1543,31 @@ void kvm_resched(struct kvm_vcpu *vcpu) 
}

EXPORT_SYMBOL_GPL(kvm_resched);



bool kvm_vcpu_yield_to(struct kvm_vcpu *target)

{

	struct pid *pid;

	struct task_struct *task = NULL;



	rcu_read_lock();

	pid = rcu_dereference(target->pid);

	if (pid)

		task = get_pid_task(target->pid, PIDTYPE_PID);

	rcu_read_unlock();

	if (!task)

		return false;

	if (task->flags & PF_VCPU) {

		put_task_struct(task);

		return false;

	}

	if (yield_to(task, 1)) {

		put_task_struct(task);

		return true;

	}

	put_task_struct(task);

	return false;

}

EXPORT_SYMBOL_GPL(kvm_vcpu_yield_to);



void kvm_vcpu_on_spin(struct kvm_vcpu *me)

{

	struct kvm *kvm = me->kvm;
@@ -1561,8 +1586,6 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me) 
	 */

	for (pass = 0; pass < 2 && !yielded; pass++) {

		kvm_for_each_vcpu(i, vcpu, kvm) {

			struct task_struct *task = NULL;

			struct pid *pid;

			if (!pass && i < last_boosted_vcpu) {

				i = last_boosted_vcpu;

				continue;
@@ -1572,24 +1595,11 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me) 
				continue;

			if (waitqueue_active(&vcpu->wq))

				continue;

			rcu_read_lock();

			pid = rcu_dereference(vcpu->pid);

			if (pid)

				task = get_pid_task(vcpu->pid, PIDTYPE_PID);

			rcu_read_unlock();

			if (!task)

				continue;

			if (task->flags & PF_VCPU) {

				put_task_struct(task);

				continue;

			}

			if (yield_to(task, 1)) {

				put_task_struct(task);

			if (kvm_vcpu_yield_to(vcpu)) {

				kvm->last_boosted_vcpu = i;

				yielded = 1;

				break;

			}

			put_task_struct(task);

		}

	}

}