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KVM: s390: provide kvm_arch_no_poll function

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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: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
This commit is contained in:
Christian Borntraeger 2019-03-05 05:30:02 -05:00
parent cdd6ad3ac6
commit 8b905d28ee
3 changed files with 19 additions and 0 deletions
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1
arch/s390/include/asm/kvm_host.h
View File

@ -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;

1
arch/s390/kvm/Kconfig
View File

@ -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---

17
arch/s390/kvm/kvm-s390.c
View File

@ -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 */