linux-kernel - Re: [PATCH v2 03/17] KVM: VMX: Move posted interrupt delivery code to common header

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Message-ID: <Z62YNrvnJ9Dzw7GE@intel.com>
Date: Thu, 13 Feb 2025 14:59:02 +0800
From: Chao Gao <chao.gao@...el.com>
To: Binbin Wu <binbin.wu@...ux.intel.com>
CC: <pbonzini@...hat.com>, <seanjc@...gle.com>, <kvm@...r.kernel.org>,
	<rick.p.edgecombe@...el.com>, <kai.huang@...el.com>,
	<adrian.hunter@...el.com>, <reinette.chatre@...el.com>,
	<xiaoyao.li@...el.com>, <tony.lindgren@...el.com>,
	<isaku.yamahata@...el.com>, <yan.y.zhao@...el.com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 03/17] KVM: VMX: Move posted interrupt delivery code
 to common header

>+/*
>+ * Send interrupt to vcpu via posted interrupt way.
>+ * 1. If target vcpu is running(non-root mode), send posted interrupt
>+ * notification to vcpu and hardware will sync PIR to vIRR atomically.

This comment primarily describes what kvm_vcpu_trigger_posted_interrupt() does.
And, it is not entirely accurate, as it is not necessarily the "hardware" that
syncs PIR to vIRR (see case 2 & 3 in the comment in
kvm_vcpu_trigger_posted_interrupt()).

How about:

/*
 * Post an interrupt to a vCPU's PIR and trigger the vCPU to process the
 * interrupt if necessary.
 */


Other than that, the patch looks good to me

Reviewed-by: Chao Gao <chao.gao@...el.com>

>+ * 2. If target vcpu isn't running(root mode), kick it to pick up the
>+ * interrupt from PIR in next vmentry.
>+ */
>+static inline void __vmx_deliver_posted_interrupt(struct kvm_vcpu *vcpu,
>+						  struct pi_desc *pi_desc, int vector)
>+{
>+	if (pi_test_and_set_pir(vector, pi_desc))
>+		return;
>+
>+	/* If a previous notification has sent the IPI, nothing to do.  */
>+	if (pi_test_and_set_on(pi_desc))
>+		return;
>+
>+	/*
>+	 * The implied barrier in pi_test_and_set_on() pairs with the smp_mb_*()
>+	 * after setting vcpu->mode in vcpu_enter_guest(), thus the vCPU is
>+	 * guaranteed to see PID.ON=1 and sync the PIR to IRR if triggering a
>+	 * posted interrupt "fails" because vcpu->mode != IN_GUEST_MODE.
>+	 */
>+	kvm_vcpu_trigger_posted_interrupt(vcpu, POSTED_INTR_VECTOR);
>+}
>+