linux-kernel - [RFC PATCH 1/3] kvm: keep track of which task is running a KVM vcpu

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Date:	Thu, 2 Dec 2010 14:43:24 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Avi Kiviti <avi@...hat.com>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>,
	Anthony Liguori <aliguori@...ux.vnet.ibm.com>
Subject: [RFC PATCH 1/3] kvm: keep track of which task is running a KVM vcpu

Keep track of which task is running a KVM vcpu.  This helps us
figure out later what task to wake up if we want to boost a
vcpu that got preempted.

Unfortunately there are no guarantees that the same task
always keeps the same vcpu, so we can only track the task
across a single "run" of the vcpu.

Signed-off-by: Rik van Riel <riel@...hat.com>

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 5fbdb55..cb73a73 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -79,6 +79,7 @@ struct kvm_vcpu {
 #endif
 	int vcpu_id;
 	struct mutex mutex;
+	struct task_struct *task;
 	int   cpu;
 	struct kvm_run *run;
 	unsigned long requests;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 050577a..2bffa47 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -741,6 +741,7 @@ void vcpu_load(struct kvm_vcpu *vcpu)
 	int cpu;
 
 	mutex_lock(&vcpu->mutex);
+	vcpu->task = current;
 	cpu = get_cpu();
 	preempt_notifier_register(&vcpu->preempt_notifier);
 	kvm_arch_vcpu_load(vcpu, cpu);
@@ -749,6 +750,7 @@ void vcpu_load(struct kvm_vcpu *vcpu)
 
 void vcpu_put(struct kvm_vcpu *vcpu)
 {
+	vcpu->task = NULL;
 	preempt_disable();
 	kvm_arch_vcpu_put(vcpu);
 	preempt_notifier_unregister(&vcpu->preempt_notifier);



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