linux-kernel - [PATCH 2/3] KVM: send IPI to vcpu only when it's in guest mode

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Message-ID: <4D243C05.7060307@cn.fujitsu.com>
Date:	Wed, 05 Jan 2011 17:38:13 +0800
From:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To:	Avi Kivity <avi@...hat.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: [PATCH 2/3] KVM: send IPI to vcpu only when it's in guest mode

We can interrupt the vcpu only when it's running in guest mode
to reduce IPI.

It looks like only ia64 and x86 need to send IPI to other vcpus, so
i only add the implementation of 'vcpu->guest_mode' in ia64, but i
don't know ia64 well, please point out the right way for me if the
implementation is incorrect

And ia64 is not tested since i don't have ia64 box

Signed-off-by: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
---
 arch/ia64/kvm/kvm-ia64.c |    2 ++
 virt/kvm/kvm_main.c      |    3 ++-
 2 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c
index 70d224d..15c11b2 100644
--- a/arch/ia64/kvm/kvm-ia64.c
+++ b/arch/ia64/kvm/kvm-ia64.c
@@ -662,6 +662,7 @@ again:
 		goto vcpu_run_fail;
 
 	srcu_read_unlock(&vcpu->kvm->srcu, idx);
+	atomic_set(&vcpu->guest_mode, 1);
 	kvm_guest_enter();
 
 	/*
@@ -683,6 +684,7 @@ again:
 	 */
 	barrier();
 	kvm_guest_exit();
+	atomic_set(&vcpu->guest_mode, 0);
 	preempt_enable();
 
 	idx = srcu_read_lock(&vcpu->kvm->srcu);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index b1b6cbb..6648c6e 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -153,7 +153,8 @@ static bool make_all_cpus_request(struct kvm *kvm, unsigned int req)
 		if (kvm_make_check_request(req, vcpu))
 			continue;
 		cpu = vcpu->cpu;
-		if (cpus != NULL && cpu != -1 && cpu != me)
+		if (cpus != NULL && cpu != -1 && cpu != me &&
+		      atomic_read(&vcpu->guest_mode))
 			cpumask_set_cpu(cpu, cpus);
 	}
 	if (unlikely(cpus == NULL))
-- 
1.7.3.4

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