linux-kernel - [PATCH v2 3/3] KVM: x86: correct async page present tracepoint

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Date:   Mon, 20 Mar 2017 21:18:55 -0700
From:   Wanpeng Li <kernellwp@...il.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Wanpeng Li <wanpeng.li@...mail.com>
Subject: [PATCH v2 3/3] KVM: x86: correct async page present tracepoint

From: Wanpeng Li <wanpeng.li@...mail.com>

After async pf setup successfully, there is a broadcast wakeup w/ special 
token 0xffffffff which tells vCPU that it should wake up all processes 
waiting for APFs though there is no real process waiting at the moment.

The async page present tracepoint print prematurely and fails to catch the 
special token setup. This patch fixes it by moving the async page present 
tracepoint after the special token setup.

Before patch:

qemu-system-x86-8499  [006] ...1  5973.473292: kvm_async_pf_ready: token 0x0 gva 0x0

After patch:

qemu-system-x86-8499  [006] ...1  5973.473292: kvm_async_pf_ready: token 0xffffffff gva 0x0

Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Radim Krčmář <rkrcmar@...hat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@...mail.com>
---
 arch/x86/kvm/x86.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 1faf620..e27eb7f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8566,11 +8566,11 @@ void kvm_arch_async_page_present(struct kvm_vcpu *vcpu,
 {
 	struct x86_exception fault;
 
-	trace_kvm_async_pf_ready(work->arch.token, work->gva);
 	if (work->wakeup_all)
 		work->arch.token = ~0; /* broadcast wakeup */
 	else
 		kvm_del_async_pf_gfn(vcpu, work->arch.gfn);
+	trace_kvm_async_pf_ready(work->arch.token, work->gva);
 
 	if ((vcpu->arch.apf.msr_val & KVM_ASYNC_PF_ENABLED) &&
 	    !apf_put_user(vcpu, KVM_PV_REASON_PAGE_READY)) {
-- 
2.7.4