linux-kernel - [PATCH 04/21] KVM: x86/xen: Initialize hrtimer in kvm_xen_init

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Message-Id: <c8e184b7acf1e073c0d6cf489031bc7d2b6304b0.1729864615.git.namcao@linutronix.de>
Date: Mon, 28 Oct 2024 08:29:23 +0100
From: Nam Cao <namcao@...utronix.de>
To: Anna-Maria Behnsen <anna-maria@...utronix.de>,
	Frederic Weisbecker <frederic@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>,
	Miguel Ojeda <ojeda@...nel.org>,
	Kees Cook <kees@...nel.org>,
	linux-kernel@...r.kernel.org
Cc: Nam Cao <namcao@...utronix.de>,
	Sean Christopherson <seanjc@...gle.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	x86@...nel.org,
	kvm@...r.kernel.org
Subject: [PATCH 04/21] KVM: x86/xen: Initialize hrtimer in kvm_xen_init_vcpu()

The hrtimer is initialized in the KVM_XEN_VCPU_SET_ATTR ioctl. That caused
problem in the past, because the hrtimer can be initialized multiple times,
which was fixed by commit af735db31285 ("KVM: x86/xen: Initialize Xen timer
only once"). This commit avoids initializing the timer multiple times by
checking the field 'function' of struct hrtimer to determine if it has
already been initialized.

Instead of "abusing" the 'function' field, move the hrtimer initialization
into kvm_xen_init_vcpu() so that it will only be initialized once.

Signed-off-by: Nam Cao <namcao@...utronix.de>
---
Cc: Sean Christopherson <seanjc@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: x86@...nel.org
Cc: kvm@...r.kernel.org
---
 arch/x86/kvm/xen.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 622fe24da910..c386fbe6b58d 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -1070,9 +1070,6 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
 			break;
 		}
 
-		if (!vcpu->arch.xen.timer.function)
-			kvm_xen_init_timer(vcpu);
-
 		/* Stop the timer (if it's running) before changing the vector */
 		kvm_xen_stop_timer(vcpu);
 		vcpu->arch.xen.timer_virq = data->u.timer.port;
@@ -2235,6 +2232,7 @@ void kvm_xen_init_vcpu(struct kvm_vcpu *vcpu)
 	vcpu->arch.xen.poll_evtchn = 0;
 
 	timer_setup(&vcpu->arch.xen.poll_timer, cancel_evtchn_poll, 0);
+	kvm_xen_init_timer(vcpu);
 
 	kvm_gpc_init(&vcpu->arch.xen.runstate_cache, vcpu->kvm);
 	kvm_gpc_init(&vcpu->arch.xen.runstate2_cache, vcpu->kvm);
-- 
2.39.5