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From:   Paolo Bonzini <pbonzini@redhat.com>
To:     linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc:     seanjc@google.com, mlevitsk@redhat.com, vkuznets@redhat.com
Subject: [PATCH v2 2/9] KVM: x86: remove return value of kvm_vcpu_block
Date:   Thu, 11 Aug 2022 17:05:58 -0400
Message-Id: <20220811210605.402337-3-pbonzini@redhat.com>
In-Reply-To: <20220811210605.402337-1-pbonzini@redhat.com>
References: <20220811210605.402337-1-pbonzini@redhat.com>
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The return value of kvm_vcpu_block will be repurposed soon to return
the state of KVM_REQ_UNHALT.  In preparation for that, get rid of the
current return value.  It is only used by kvm_vcpu_halt to decide whether
the call resulted in a wait, but the same effect can be obtained with
a single round of polling.

No functional change intended, apart from practically indistinguishable
changes to the polling behavior.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 include/linux/kvm_host.h |  2 +-
 virt/kvm/kvm_main.c      | 45 +++++++++++++++++-----------------------
 2 files changed, 20 insertions(+), 27 deletions(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 1c480b1821e1..e7bd48d15db8 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1339,7 +1339,7 @@ void kvm_sigset_activate(struct kvm_vcpu *vcpu);
 void kvm_sigset_deactivate(struct kvm_vcpu *vcpu);
 
 void kvm_vcpu_halt(struct kvm_vcpu *vcpu);
-bool kvm_vcpu_block(struct kvm_vcpu *vcpu);
+void kvm_vcpu_block(struct kvm_vcpu *vcpu);
 void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu);
 void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu);
 bool kvm_vcpu_wake_up(struct kvm_vcpu *vcpu);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 515dfe9d3bcf..1f049c1d01b4 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3429,10 +3429,9 @@ static int kvm_vcpu_check_block(struct kvm_vcpu *vcpu)
  * pending.  This is mostly used when halting a vCPU, but may also be used
  * directly for other vCPU non-runnable states, e.g. x86's Wait-For-SIPI.
  */
-bool kvm_vcpu_block(struct kvm_vcpu *vcpu)
+void kvm_vcpu_block(struct kvm_vcpu *vcpu)
 {
 	struct rcuwait *wait = kvm_arch_vcpu_get_wait(vcpu);
-	bool waited = false;
 
 	vcpu->stat.generic.blocking = 1;
 
@@ -3447,7 +3446,6 @@ bool kvm_vcpu_block(struct kvm_vcpu *vcpu)
 		if (kvm_vcpu_check_block(vcpu) < 0)
 			break;
 
-		waited = true;
 		schedule();
 	}
 
@@ -3457,8 +3455,6 @@ bool kvm_vcpu_block(struct kvm_vcpu *vcpu)
 	preempt_enable();
 
 	vcpu->stat.generic.blocking = 0;
-
-	return waited;
 }
 
 static inline void update_halt_poll_stats(struct kvm_vcpu *vcpu, ktime_t start,
@@ -3493,35 +3489,32 @@ void kvm_vcpu_halt(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;
+	ktime_t start, cur, poll_end, stop;
 	bool waited = false;
 	u64 halt_ns;
 
 	start = cur = poll_end = ktime_get();
-	if (do_halt_poll) {
-		ktime_t stop = ktime_add_ns(start, vcpu->halt_poll_ns);
+	stop = do_halt_poll ? start : ktime_add_ns(start, vcpu->halt_poll_ns);
 
-		do {
-			/*
-			 * This sets KVM_REQ_UNHALT if an interrupt
-			 * arrives.
-			 */
-			if (kvm_vcpu_check_block(vcpu) < 0)
-				goto out;
-			cpu_relax();
-			poll_end = cur = ktime_get();
-		} while (kvm_vcpu_can_poll(cur, stop));
-	}
+	do {
+		/*
+		 * This sets KVM_REQ_UNHALT if an interrupt
+		 * arrives.
+		 */
+		if (kvm_vcpu_check_block(vcpu) < 0)
+			goto out;
+		cpu_relax();
+		poll_end = cur = ktime_get();
+	} while (kvm_vcpu_can_poll(cur, stop));
 
-	waited = kvm_vcpu_block(vcpu);
+	waited = true;
+	kvm_vcpu_block(vcpu);
 
 	cur = ktime_get();
-	if (waited) {
-		vcpu->stat.generic.halt_wait_ns +=
-			ktime_to_ns(cur) - ktime_to_ns(poll_end);
-		KVM_STATS_LOG_HIST_UPDATE(vcpu->stat.generic.halt_wait_hist,
-				ktime_to_ns(cur) - ktime_to_ns(poll_end));
-	}
+	vcpu->stat.generic.halt_wait_ns +=
+		ktime_to_ns(cur) - ktime_to_ns(poll_end);
+	KVM_STATS_LOG_HIST_UPDATE(vcpu->stat.generic.halt_wait_hist,
+				  ktime_to_ns(cur) - ktime_to_ns(poll_end));
 out:
 	/* The total time the vCPU was "halted", including polling time. */
 	halt_ns = ktime_to_ns(cur) - ktime_to_ns(start);
-- 
2.31.1