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From: Wanpeng Li <kernellwp@gmail.com>
To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: "Paolo Bonzini" <pbonzini@redhat.com>,
	"Radim Krčmář" <rkrcmar@redhat.com>
Subject: [PATCH RESEND v2] KVM: X86: Implement PV sched yield hypercall
Date: Tue, 28 May 2019 10:15:52 +0800	[thread overview]
Message-ID: <1559009752-8536-1-git-send-email-wanpengli@tencent.com> (raw)
In-Reply-To: <1559004795-19927-3-git-send-email-wanpengli@tencent.com>

From: Wanpeng Li <wanpengli@tencent.com>

The target vCPUs are in runnable state after vcpu_kick and suitable 
as a yield target. This patch implements the sched yield hypercall.

17% performance increase of ebizzy benchmark can be observed in an 
over-subscribe environment. (w/ kvm-pv-tlb disabled, testing TLB flush 
call-function IPI-many since call-function is not easy to be trigged 
by userspace workload).

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
---
 arch/x86/kvm/x86.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e7e57de..2f9ec08 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7172,6 +7172,28 @@ void kvm_vcpu_deactivate_apicv(struct kvm_vcpu *vcpu)
 	kvm_x86_ops->refresh_apicv_exec_ctrl(vcpu);
 }
 
+void kvm_sched_yield(struct kvm *kvm, u64 dest_id)
+{
+	struct kvm_vcpu *target;
+	struct kvm_apic_map *map;
+
+	rcu_read_lock();
+	map = rcu_dereference(kvm->arch.apic_map);
+
+	if (unlikely(!map))
+		goto out;
+
+	if (map->phys_map[dest_id]->vcpu) {
+		target = map->phys_map[dest_id]->vcpu;
+		rcu_read_unlock();
+		kvm_vcpu_yield_to(target);
+	}
+
+out:
+	if (!target)
+		rcu_read_unlock();
+}
+
 int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
 {
 	unsigned long nr, a0, a1, a2, a3, ret;
@@ -7218,6 +7240,10 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
 	case KVM_HC_SEND_IPI:
 		ret = kvm_pv_send_ipi(vcpu->kvm, a0, a1, a2, a3, op_64_bit);
 		break;
+	case KVM_HC_SCHED_YIELD:
+		kvm_sched_yield(vcpu->kvm, a0);
+		ret = 0;
+		break;
 	default:
 		ret = -KVM_ENOSYS;
 		break;
-- 
2.7.4


  reply	other threads:[~2019-05-28  2:16 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-28  0:53 [PATCH v2 0/3] KVM: Yield to IPI target if necessary Wanpeng Li
2019-05-28  0:53 ` [PATCH v2 1/3] KVM: X86: Implement PV sched yield in linux guest Wanpeng Li
2019-05-28  0:53 ` [PATCH v2 2/3] KVM: X86: Implement PV sched yield hypercall Wanpeng Li
2019-05-28  2:15   ` Wanpeng Li [this message]
2019-05-28  6:08     ` [PATCH RESEND v2] " kbuild test robot
2019-05-28  6:14       ` Wanpeng Li
2019-05-28  7:23     ` kbuild test robot
2019-05-28  7:50   ` [PATCH RESEND v2 0/3] KVM: Yield to IPI target if necessary Wanpeng Li
2019-05-28  7:50     ` [PATCH RESEND v2 1/3] KVM: X86: Implement PV sched yield in linux guest Wanpeng Li
2019-05-28  7:50     ` [PATCH RESEND v2 2/3] KVM: X86: Implement PV sched yield hypercall Wanpeng Li
2019-05-28  7:50     ` [PATCH RESEND v2 3/3] KVM: X86: Expose PV_SCHED_YIELD CPUID feature bit to guest Wanpeng Li
2019-05-28  9:11   ` [PATCH v2 2/3] KVM: X86: Implement PV sched yield hypercall Christian Borntraeger
2019-05-28  9:57     ` Wanpeng Li
2019-05-29 12:28   ` Liran Alon
2019-05-30  1:09     ` Wanpeng Li
2019-05-28  0:53 ` [PATCH v2 3/3] KVM: X86: Expose PV_SCHED_YIELD CPUID feature bit to guest Wanpeng Li

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