linux-kernel - [PATCH 1/2] KVM: VMX: Assert that IRQs are disabled when putting vCPU on PI wakeup list

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Message-ID: <20250401154727.835231-2-seanjc@google.com>
Date: Tue,  1 Apr 2025 08:47:26 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Yan Zhao <yan.y.zhao@...el.com>
Subject: [PATCH 1/2] KVM: VMX: Assert that IRQs are disabled when putting vCPU
 on PI wakeup list

Assert that IRQs are already disabled when putting a vCPU on a CPU's PI
wakeup list, as opposed to saving/disabling+restoring IRQs.  KVM relies on
IRQs being disabled until the vCPU task is fully scheduled out, i.e. until
the scheduler has dropped all of its per-CPU locks (e.g. for the runqueue),
as attempting to wake the task while it's being scheduled out could lead
to deadlock.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/vmx/posted_intr.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c
index ec08fa3caf43..840d435229a8 100644
--- a/arch/x86/kvm/vmx/posted_intr.c
+++ b/arch/x86/kvm/vmx/posted_intr.c
@@ -148,9 +148,8 @@ static void pi_enable_wakeup_handler(struct kvm_vcpu *vcpu)
 	struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu);
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	struct pi_desc old, new;
-	unsigned long flags;
 
-	local_irq_save(flags);
+	lockdep_assert_irqs_disabled();
 
 	raw_spin_lock(&per_cpu(wakeup_vcpus_on_cpu_lock, vcpu->cpu));
 	list_add_tail(&vmx->pi_wakeup_list,
@@ -176,8 +175,6 @@ static void pi_enable_wakeup_handler(struct kvm_vcpu *vcpu)
 	 */
 	if (pi_test_on(&new))
 		__apic_send_IPI_self(POSTED_INTR_WAKEUP_VECTOR);
-
-	local_irq_restore(flags);
 }
 
 static bool vmx_needs_pi_wakeup(struct kvm_vcpu *vcpu)
-- 
2.49.0.472.ge94155a9ec-goog