linux-kernel - [RFC PATCH 07/10] KVM: VMX: fix invalid cpu passed to smp_call_function

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Message-ID: <20121204085533.25919.54306.stgit@srivatsabhat.in.ibm.com>
Date:	Tue, 04 Dec 2012 14:25:38 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	tglx@...utronix.de, peterz@...radead.org,
	paulmck@...ux.vnet.ibm.com, rusty@...tcorp.com.au,
	mingo@...nel.org, akpm@...ux-foundation.org, namhyung@...nel.org,
	vincent.guittot@...aro.org
Cc:	sbw@....edu, tj@...nel.org, amit.kucheria@...aro.org,
	rostedt@...dmis.org, rjw@...k.pl, srivatsa.bhat@...ux.vnet.ibm.com,
	wangyun@...ux.vnet.ibm.com, xiaoguangrong@...ux.vnet.ibm.com,
	nikunj@...ux.vnet.ibm.com, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [RFC PATCH 07/10] KVM: VMX: fix invalid cpu passed to
 smp_call_function_single

From: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>

In loaded_vmcs_clear, loaded_vmcs->cpu is the fist parameter passed to
smp_call_function_single, if the target cpu is downing (doing cpu hot remove),
loaded_vmcs->cpu can become -1 then -1 is passed to smp_call_function_single

It can be triggered when vcpu is being destroyed, loaded_vmcs_clear is called
in the preemptionable context

Signed-off-by: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
---

 arch/x86/kvm/vmx.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index f858159..9dc562a 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1007,9 +1007,11 @@ static void __loaded_vmcs_clear(void *arg)
 
 static void loaded_vmcs_clear(struct loaded_vmcs *loaded_vmcs)
 {
-	if (loaded_vmcs->cpu != -1)
-		smp_call_function_single(
-			loaded_vmcs->cpu, __loaded_vmcs_clear, loaded_vmcs, 1);
+	int cpu = loaded_vmcs->cpu;
+
+	if (cpu != -1)
+		smp_call_function_single(cpu,
+			 __loaded_vmcs_clear, loaded_vmcs, 1);
 }
 
 static inline void vpid_sync_vcpu_single(struct vcpu_vmx *vmx)

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