linux-kernel - [PATCH 02/14] KVM: Update halt-polling stats if and only if halt-polling was attempted

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Date:   Fri, 24 Sep 2021 17:55:16 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Marc Zyngier <maz@...nel.org>, Huacai Chen <chenhuacai@...nel.org>,
        Aleksandar Markovic <aleksandar.qemu.devel@...il.com>,
        Paul Mackerras <paulus@...abs.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        David Hildenbrand <david@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-mips@...r.kernel.org, kvm@...r.kernel.org,
        kvm-ppc@...r.kernel.org, linux-kernel@...r.kernel.org,
        David Matlack <dmatlack@...gle.com>,
        Jing Zhang <jingzhangos@...gle.com>
Subject: [PATCH 02/14] KVM: Update halt-polling stats if and only if
 halt-polling was attempted

Don't update halt-polling stats if halt-polling wasn't attempted.  This
is a nop as @poll_ns is guaranteed to be '0' (poll_end == start), but it
will allow a future patch to move the histogram stats into the helper to
resolve a discrepancy in what is considered a "successful" halt-poll.

No functional change intended.

Cc: David Matlack <dmatlack@...gle.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 virt/kvm/kvm_main.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 768a4cbb26a6..8b33f5045b4d 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3214,6 +3214,7 @@ update_halt_poll_stats(struct kvm_vcpu *vcpu, u64 poll_ns, bool waited)
 void kvm_vcpu_block(struct kvm_vcpu *vcpu)
 {
 	bool halt_poll_allowed = !kvm_arch_no_poll(vcpu);
+	bool do_halt_poll = halt_poll_allowed && vcpu->halt_poll_ns;
 	ktime_t start, cur, poll_end;
 	bool waited = false;
 	u64 block_ns;
@@ -3221,7 +3222,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
 	kvm_arch_vcpu_blocking(vcpu);
 
 	start = cur = poll_end = ktime_get();
-	if (vcpu->halt_poll_ns && halt_poll_allowed) {
+	if (do_halt_poll) {
 		ktime_t stop = ktime_add_ns(ktime_get(), vcpu->halt_poll_ns);
 
 		++vcpu->stat.generic.halt_attempted_poll;
@@ -3273,8 +3274,9 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
 	kvm_arch_vcpu_unblocking(vcpu);
 	block_ns = ktime_to_ns(cur) - ktime_to_ns(start);
 
-	update_halt_poll_stats(
-		vcpu, ktime_to_ns(ktime_sub(poll_end, start)), waited);
+	if (do_halt_poll)
+		update_halt_poll_stats(
+			vcpu, ktime_to_ns(ktime_sub(poll_end, start)), waited);
 
 	if (halt_poll_allowed) {
 		if (!vcpu_valid_wakeup(vcpu)) {
-- 
2.33.0.685.g46640cef36-goog