[PATCH v3 07/62] KVM: SVM: Delete IRTE link from previous vCPU irrespective of new routing

[Sean Christopherson]

Delete the IRTE link from the previous vCPU irrespective of the new
routing state, i.e. even if the IRTE won't be configured to post IRQs to a
vCPU.  Whether or not the new route is postable as no bearing on the *old*
route.  Failure to delete the link can result in KVM incorrectly updating
the IRTE, e.g. if the "old" vCPU is scheduled in/out.

Fixes: 411b44ba80ab ("svm: Implements update_pi_irte hook to setup posted interrupt")
Tested-by: Sairaj Kodilkar <sarunkod at amd.com>
Signed-off-by: Sean Christopherson <seanjc at google.com>
---
 arch/x86/kvm/svm/avic.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index 4e8380d2f017..c981ce764b45 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -861,6 +861,12 @@ int avic_pi_update_irte(struct kvm_kernel_irqfd *irqfd, struct kvm *kvm,
 	if (!kvm_arch_has_assigned_device(kvm) || !kvm_arch_has_irq_bypass())
 		return 0;
 
+	/*
+	 * If the IRQ was affined to a different vCPU, remove the IRTE metadata
+	 * from the *previous* vCPU's list.
+	 */
+	svm_ir_list_del(irqfd);
+
 	pr_debug("SVM: %s: host_irq=%#x, guest_irq=%#x, set=%#x\n",
 		 __func__, host_irq, guest_irq, set);
 
@@ -883,8 +889,6 @@ int avic_pi_update_irte(struct kvm_kernel_irqfd *irqfd, struct kvm *kvm,
 
 		WARN_ON_ONCE(new && memcmp(e, new, sizeof(*new)));
 
-		svm_ir_list_del(irqfd);
-
 		/**
 		 * Here, we setup with legacy mode in the following cases:
 		 * 1. When cannot target interrupt to a specific vcpu.
-- 
2.50.0.rc1.591.g9c95f17f64-goog