linux-kernel - Re: [PATCH v5 1/3] KVM: x86: Isolate edge vs. level check in userspace I/O APIC route scanning

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Message-ID: <5ca74373f6bd09f1f0a4deff8867cfb07ffe430d.camel@intel.com>
Date: Tue, 4 Mar 2025 09:42:36 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "pbonzini@...hat.com" <pbonzini@...hat.com>, "seanjc@...gle.com"
	<seanjc@...gle.com>
CC: "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"xuyun_xy.xy@...ux.alibaba.com" <xuyun_xy.xy@...ux.alibaba.com>,
	"zijie.wei@...ux.alibaba.com" <zijie.wei@...ux.alibaba.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 1/3] KVM: x86: Isolate edge vs. level check in
 userspace I/O APIC route scanning

On Mon, 2025-03-03 at 17:33 -0800, Sean Christopherson wrote:
> Extract and isolate the trigger mode check in kvm_scan_ioapic_routes() in
> anticipation of moving destination matching logic to a common helper (for
> userspace vs. in-kernel I/O APIC emulation).
> 
> No functional change intended.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

Reviewed-by: Kai Huang <kai.huang@...el.com>

> ---
>  arch/x86/kvm/irq_comm.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c
> index 8136695f7b96..866f84392797 100644
> --- a/arch/x86/kvm/irq_comm.c
> +++ b/arch/x86/kvm/irq_comm.c
> @@ -424,10 +424,12 @@ void kvm_scan_ioapic_routes(struct kvm_vcpu *vcpu,
>  
>  			kvm_set_msi_irq(vcpu->kvm, entry, &irq);
>  
> -			if (irq.trig_mode &&
> -			    (kvm_apic_match_dest(vcpu, NULL, APIC_DEST_NOSHORT,
> -						 irq.dest_id, irq.dest_mode) ||
> -			     kvm_apic_pending_eoi(vcpu, irq.vector)))
> +			if (!irq.trig_mode)
> +				continue;

Perhaps take this chance to make it explicit?

			if (irq.trig_mode != IOAPIC_LEVEL_TRIG)
				continue;

kvm_ioapic_scan_entry() also checks against IOAPIC_LEVEL_TRIG explicitly.

> +
> +			if (kvm_apic_match_dest(vcpu, NULL, APIC_DEST_NOSHORT,
> +						irq.dest_id, irq.dest_mode) ||
> +			     kvm_apic_pending_eoi(vcpu, irq.vector))
>  				__set_bit(irq.vector, ioapic_handled_vectors);
>  		}
>  	}