Subject: Re: linux-next: build failure after merge of the kvm tree

From: Wanpeng Li <[email-masked]>
Date: Tue, 8 Sep 2015 10:10:13 +0800

Hi Paolo, Stephen,
On 9/8/15 9:35 AM, Stephen Rothwell wrote:
> Hi all,
>
> After merging the kvm tree, today's linux-next build (powerpc
> ppc64_defconfig) failed like this:
>
> arch/powerpc/kvm/../../../virt/kvm/kvm_main.c: In function 'grow_halt_poll_ns':
> arch/powerpc/kvm/../../../virt/kvm/kvm_main.c:1931:2: error: implicit declaration of function 'trace_kvm_halt_poll_ns_grow' [-Werror=implicit-function-declaration]
>    trace_kvm_halt_poll_ns_grow(vcpu->vcpu_id, val, old);
>    ^
> arch/powerpc/kvm/../../../virt/kvm/kvm_main.c: In function 'shrink_halt_poll_ns':
> arch/powerpc/kvm/../../../virt/kvm/kvm_main.c:1945:2: error: implicit declaration of function 'trace_kvm_halt_poll_ns_shrink' [-Werror=implicit-function-declaration]
>    trace_kvm_halt_poll_ns_shrink(vcpu->vcpu_id, val, old);
>    ^
>
> Caused by commit
>
>    2cbd78244fb2 ("KVM: trace kvm_halt_poll_ns grow/shrink")
>
> I have reverted that commit for today.

I miss place the trace codes under CONFIG_KVM_ASYNC_PF, the patch in the 
attachment rewrite the commit and fix it. Sorry for that.

Regards,
Wanpeng Li
>>From c06ca8fec43a7ccc1fe265afe8b2fd3b84085368 Mon Sep 17 00:00:00 2001
From: Wanpeng Li <[email-masked]>
Date: Tue, 8 Sep 2015 10:03:38 +0800
Subject: [PATCH] KVM: trace kvm_halt_poll_ns grow/shrink

Tracepoint for dynamic halt_pool_ns, fired on every potential change.

Signed-off-by: Wanpeng Li <[email-masked]>
---
 include/trace/events/kvm.h | 30 ++++++++++++++++++++++++++++++
 virt/kvm/kvm_main.c        |  8 ++++++--
 2 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h
index a44062d..d6f8322 100644
--- a/include/trace/events/kvm.h
+++ b/include/trace/events/kvm.h
@@ -358,6 +358,36 @@ TRACE_EVENT(
 
 #endif
 
+TRACE_EVENT(kvm_halt_poll_ns,
+	TP_PROTO(bool grow, unsigned int vcpu_id, int new, int old),
+	TP_ARGS(grow, vcpu_id, new, old),
+
+	TP_STRUCT__entry(
+		__field(bool, grow)
+		__field(unsigned int, vcpu_id)
+		__field(int, new)
+		__field(int, old)
+	),
+
+	TP_fast_assign(
+		__entry->grow           = grow;
+		__entry->vcpu_id        = vcpu_id;
+		__entry->new            = new;
+		__entry->old            = old;
+	),
+
+	TP_printk("vcpu %u: halt_poll_ns %d (%s %d)",
+			__entry->vcpu_id,
+			__entry->new,
+			__entry->grow ? "grow" : "shrink",
+			__entry->old)
+);
+
+#define trace_kvm_halt_poll_ns_grow(vcpu_id, new, old) \
+	trace_kvm_halt_poll_ns(true, vcpu_id, new, old)
+#define trace_kvm_halt_poll_ns_shrink(vcpu_id, new, old) \
+	trace_kvm_halt_poll_ns(false, vcpu_id, new, old)
+
 #endif /* _TRACE_KVM_MAIN_H */
 
 /* This part must be outside protection */
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 8ab49cf..4662a88 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1918,8 +1918,9 @@ EXPORT_SYMBOL_GPL(kvm_vcpu_mark_page_dirty);
 
 static void grow_halt_poll_ns(struct kvm_vcpu *vcpu)
 {
-	int val = vcpu->halt_poll_ns;
+	int old, val;
 
+	old = val = vcpu->halt_poll_ns;
 	/* 10us base */
 	if (val == 0 && halt_poll_ns_grow)
 		val = 10000;
@@ -1927,18 +1928,21 @@ static void grow_halt_poll_ns(struct kvm_vcpu *vcpu)
 		val *= halt_poll_ns_grow;
 
 	vcpu->halt_poll_ns = val;
+	trace_kvm_halt_poll_ns_grow(vcpu->vcpu_id, val, old);
 }
 
 static void shrink_halt_poll_ns(struct kvm_vcpu *vcpu)
 {
-	int val = vcpu->halt_poll_ns;
+	int old, val;
 
+	old = val = vcpu->halt_poll_ns;
 	if (halt_poll_ns_shrink == 0)
 		val = 0;
 	else
 		val /= halt_poll_ns_shrink;
 
 	vcpu->halt_poll_ns = val;
+	trace_kvm_halt_poll_ns_shrink(vcpu->vcpu_id, val, old);
 }
 
 static int kvm_vcpu_check_block(struct kvm_vcpu *vcpu)
-- 
1.9.1