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Date: Thu, 22 Apr 2021 00:08:31 +0900
From: Kenta Ishiguro <kentaishiguro@...ab.ics.keio.ac.jp>
To: Paolo Bonzini <pbonzini@...hat.com>
Cc: Sean Christopherson <seanjc@...gle.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>,
David Hildenbrand <david@...hat.com>, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org, pl@...ab.ics.keio.ac.jp,
kono@...ab.ics.keio.ac.jp,
Kenta Ishiguro <kentaishiguro@...ab.ics.keio.ac.jp>
Subject: [RFC PATCH 2/2] Boost vCPUs based on IPI-sender and receiver information
This commit monitors IPI communication between vCPUs and leverages the
relationship between vCPUs to select boost candidates.
Cc: David Hildenbrand <david@...hat.com>
Signed-off-by: Kenta Ishiguro <kentaishiguro@...ab.ics.keio.ac.jp>
---
arch/x86/kvm/lapic.c | 14 ++++++++++++++
arch/x86/kvm/vmx/vmx.c | 2 ++
include/linux/kvm_host.h | 5 +++++
virt/kvm/kvm_main.c | 26 ++++++++++++++++++++++++--
4 files changed, 45 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index cc369b9ad8f1..c8d967ddecf9 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1269,6 +1269,18 @@ void kvm_apic_set_eoi_accelerated(struct kvm_vcpu *vcpu, int vector)
}
EXPORT_SYMBOL_GPL(kvm_apic_set_eoi_accelerated);
+static void mark_ipi_receiver(struct kvm_lapic *apic, struct kvm_lapic_irq *irq)
+{
+ struct kvm_vcpu *dest_vcpu;
+ u64 prev_ipi_received;
+
+ dest_vcpu = kvm_get_vcpu_by_id(apic->vcpu->kvm, irq->dest_id);
+ if (READ_ONCE(dest_vcpu->sched_outed)) {
+ prev_ipi_received = READ_ONCE(dest_vcpu->ipi_received);
+ WRITE_ONCE(dest_vcpu->ipi_received, prev_ipi_received | (1 << apic->vcpu->vcpu_id));
+ }
+}
+
void kvm_apic_send_ipi(struct kvm_lapic *apic, u32 icr_low, u32 icr_high)
{
struct kvm_lapic_irq irq;
@@ -1287,6 +1299,8 @@ void kvm_apic_send_ipi(struct kvm_lapic *apic, u32 icr_low, u32 icr_high)
trace_kvm_apic_ipi(icr_low, irq.dest_id);
+ mark_ipi_receiver(apic, &irq);
+
kvm_irq_delivery_to_apic(apic->vcpu->kvm, apic, &irq, NULL);
}
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 29b40e092d13..ced50935a38b 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6718,6 +6718,8 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
vmcs_write32(PLE_WINDOW, vmx->ple_window);
}
+ WRITE_ONCE(vcpu->ipi_received, 0);
+
/*
* We did this in prepare_switch_to_guest, because it needs to
* be within srcu_read_lock.
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 1b65e7204344..6726aeec03e7 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -320,6 +320,11 @@ struct kvm_vcpu {
#endif
bool preempted;
bool ready;
+ bool sched_outed;
+ /*
+ * The current implementation of strict boost supports up to 64 vCPUs
+ */
+ u64 ipi_received;
struct kvm_vcpu_arch arch;
struct kvm_dirty_ring dirty_ring;
};
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 383df23514b9..08e629957e7e 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -413,6 +413,10 @@ static void kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id)
kvm_vcpu_set_dy_eligible(vcpu, false);
vcpu->preempted = false;
vcpu->ready = false;
+
+ vcpu->sched_outed = false;
+ vcpu->ipi_received = 0;
+
preempt_notifier_init(&vcpu->preempt_notifier, &kvm_preempt_ops);
}
@@ -3011,6 +3015,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool yield_to_kernel_mode)
int try = 3;
int pass;
int i;
+ u64 prev_ipi_received;
kvm_vcpu_set_in_spin_loop(me, true);
/*
@@ -3031,12 +3036,25 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool yield_to_kernel_mode)
continue;
if (vcpu == me)
continue;
+ prev_ipi_received = READ_ONCE(vcpu->ipi_received);
+ if (!READ_ONCE(vcpu->preempted) &&
+ !(prev_ipi_received & (1 << me->vcpu_id))) {
+ WRITE_ONCE(vcpu->ipi_received,
+ prev_ipi_received | (1 << me->vcpu_id));
+ continue;
+ }
if (rcuwait_active(&vcpu->wait) &&
!vcpu_dy_runnable(vcpu))
continue;
if (READ_ONCE(vcpu->preempted) && yield_to_kernel_mode &&
- !kvm_arch_vcpu_in_kernel(vcpu))
- continue;
+ !kvm_arch_vcpu_in_kernel(vcpu)) {
+ prev_ipi_received = READ_ONCE(vcpu->ipi_received);
+ if (!(prev_ipi_received & (1 << me->vcpu_id))) {
+ WRITE_ONCE(vcpu->ipi_received,
+ prev_ipi_received | (1 << me->vcpu_id));
+ continue;
+ }
+ }
if (!kvm_vcpu_eligible_for_directed_yield(vcpu))
continue;
@@ -4859,6 +4877,9 @@ static void kvm_sched_in(struct preempt_notifier *pn, int cpu)
WRITE_ONCE(vcpu->preempted, false);
WRITE_ONCE(vcpu->ready, false);
+ WRITE_ONCE(vcpu->sched_outed, false);
+ WRITE_ONCE(vcpu->ipi_received, 0);
+
__this_cpu_write(kvm_running_vcpu, vcpu);
kvm_arch_sched_in(vcpu, cpu);
kvm_arch_vcpu_load(vcpu, cpu);
@@ -4873,6 +4894,7 @@ static void kvm_sched_out(struct preempt_notifier *pn,
WRITE_ONCE(vcpu->preempted, true);
WRITE_ONCE(vcpu->ready, true);
}
+ WRITE_ONCE(vcpu->sched_outed, true);
kvm_arch_vcpu_put(vcpu);
__this_cpu_write(kvm_running_vcpu, NULL);
}
--
2.30.2
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