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From:   Vitaly Kuznetsov <vkuznets@redhat.com>
To:     Wanpeng Li <kernellwp@gmail.com>, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>
Subject: Re: [PATCH 2/2] KVM: LAPIC: Don't need to clear IPI delivery status for x2apic
In-Reply-To: <1585290240-18643-2-git-send-email-wanpengli@tencent.com>
References: <1585290240-18643-1-git-send-email-wanpengli@tencent.com> <1585290240-18643-2-git-send-email-wanpengli@tencent.com>
Date:   Fri, 27 Mar 2020 10:06:57 +0100
Message-ID: <87eete415a.fsf@vitty.brq.redhat.com>
MIME-Version: 1.0
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Sender: linux-kernel-owner@vger.kernel.org
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Wanpeng Li <kernellwp@gmail.com> writes:

> From: Wanpeng Li <wanpengli@tencent.com>
>
> IPI delivery status field is not present for x2apic, don't need 
> to clear IPI delivery status for x2apic.
>
> Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
> ---
>  arch/x86/kvm/lapic.c | 3 ++-
>  arch/x86/kvm/x86.c   | 1 -
>  2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 88929b1..f6d69e2 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -1942,7 +1942,8 @@ int kvm_lapic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val)
>  	}
>  	case APIC_ICR:
>  		/* No delay here, so we always clear the pending bit */

'Always' in the comment above now reads a bit odd, I'd suggest modifying
it to 'Immediately clear Delivery Status field in xAPIC mode' - or just
drop it altogeter.

> -		val &= ~(1 << 12);
> +		if (!apic_x2apic_mode(apic))
> +			val &= ~(1 << 12);
>  		kvm_apic_send_ipi(apic, val, kvm_lapic_get_reg(apic, APIC_ICR2));
>  		kvm_lapic_set_reg(apic, APIC_ICR, val);
>  		break;
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 495709f..6ced0e1 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1562,7 +1562,6 @@ static int handle_fastpath_set_x2apic_icr_irqoff(struct kvm_vcpu *vcpu, u64 data
>  		((data & APIC_MODE_MASK) == APIC_DM_FIXED) &&
>  		((u32)(data >> 32) != X2APIC_BROADCAST)) {
>  
> -		data &= ~(1 << 12);
>  		kvm_apic_send_ipi(vcpu->arch.apic, (u32)data, (u32)(data >> 32));
>  		kvm_lapic_set_reg(vcpu->arch.apic, APIC_ICR2, (u32)(data >> 32));
>  		kvm_lapic_set_reg(vcpu->arch.apic, APIC_ICR, (u32)data);

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>

-- 
Vitaly