From: Christian Borntraeger <borntraeger@de.ibm.com>
Date: Tue, 5 Mar 2019 05:30:02 -0500
Subject: KVM: s390: provide kvm_arch_no_poll function
Patch-mainline: v5.2-rc1
Git-commit: 8b905d28ee17795c939813b2f6947829774619b9
References: bsc#1119222

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>
Acked-by: Liang Yan <lyan@suse.com>
---
 arch/s390/include/asm/kvm_host.h |    1 +
 arch/s390/kvm/Kconfig            |    1 +
 arch/s390/kvm/kvm-s390.c         |   17 +++++++++++++++++
 3 files changed, 19 insertions(+)

--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -303,6 +303,7 @@ 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;
--- a/arch/s390/kvm/Kconfig
+++ b/arch/s390/kvm/Kconfig
@@ -29,6 +29,7 @@ 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---
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -73,6 +73,7 @@ struct kvm_stats_debugfs_item debugfs_en
 	{ "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) },
@@ -159,6 +160,11 @@ MODULE_PARM_DESC(nested, "Nested virtual
  */
 #define SIZE_INTERNAL 16
 
+/* 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");
+
 /*
  * Base feature mask that defines default mask for facilities. Consists of the
  * defines in FACILITIES_KVM and the non-hypervisor managed bits.
@@ -2659,6 +2665,17 @@ static void kvm_gmap_notifier(struct gma
 	}
 }
 
+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 */