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Commit 8b905d28 authored by Christian Borntraeger's avatar Christian Borntraeger
Browse files

KVM: s390: provide kvm_arch_no_poll function 



We do track the current steal time of the host CPUs. Let us use
this value to disable halt polling if the steal time goes beyond
a configured value.

Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Acked-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: default avatarCornelia Huck <cohuck@redhat.com>
Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
parent cdd6ad3a

arch/s390/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -313,6 +313,7 @@ struct kvm_vcpu_stat { 
	u64 halt_successful_poll;

	u64 halt_attempted_poll;

	u64 halt_poll_invalid;

	u64 halt_no_poll_steal;

	u64 halt_wakeup;

	u64 instruction_lctl;

	u64 instruction_lctlg;

arch/s390/kvm/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -31,6 +31,7 @@ config KVM 
	select HAVE_KVM_IRQFD

	select HAVE_KVM_IRQ_ROUTING

	select HAVE_KVM_INVALID_WAKEUPS

	select HAVE_KVM_NO_POLL

	select SRCU

	select KVM_VFIO

	---help---

arch/s390/kvm/kvm-s390.c

+17 −0
Original line number Diff line number Diff line
@@ -75,6 +75,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = { 
	{ "halt_successful_poll", VCPU_STAT(halt_successful_poll) },

	{ "halt_attempted_poll", VCPU_STAT(halt_attempted_poll) },

	{ "halt_poll_invalid", VCPU_STAT(halt_poll_invalid) },

	{ "halt_no_poll_steal", VCPU_STAT(halt_no_poll_steal) },

	{ "halt_wakeup", VCPU_STAT(halt_wakeup) },

	{ "instruction_lctlg", VCPU_STAT(instruction_lctlg) },

	{ "instruction_lctl", VCPU_STAT(instruction_lctl) },
@@ -177,6 +178,11 @@ static int hpage; 
module_param(hpage, int, 0444);

MODULE_PARM_DESC(hpage, "1m huge page backing support");



/* maximum percentage of steal time for polling.  >100 is treated like 100 */

static u8 halt_poll_max_steal = 10;

module_param(halt_poll_max_steal, byte, 0644);

MODULE_PARM_DESC(hpage, "Maximum percentage of steal time to allow polling");



/*

 * For now we handle at most 16 double words as this is what the s390 base

 * kernel handles and stores in the prefix page. If we ever need to go beyond
@@ -3166,6 +3172,17 @@ static void kvm_gmap_notifier(struct gmap *gmap, unsigned long start, 
	}

}



bool kvm_arch_no_poll(struct kvm_vcpu *vcpu)

{

	/* do not poll with more than halt_poll_max_steal percent of steal time */

	if (S390_lowcore.avg_steal_timer * 100 / (TICK_USEC << 12) >=

	    halt_poll_max_steal) {

		vcpu->stat.halt_no_poll_steal++;

		return true;

	}

	return false;

}



int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)

{

	/* kvm common code refers to this, but never calls it */