linux-kernel - Re: [PATCH 1/1] KVM: ioapic: Record edge-triggered interrupts delivery status.

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Date:	Wed, 24 Dec 2014 16:29:22 +0100
From:	Jan Kiszka <jan.kiszka@....de>
To:	Wincy Van <fanwenyi0529@...il.com>, pbonzini@...hat.com,
	bsd@...hat.com
CC:	yang.z.zhang@...el.com, wanpeng.li@...ux.intel.com,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] KVM: ioapic: Record edge-triggered interrupts delivery
 status.

On 2014-12-24 04:14, Wincy Van wrote:
> This patch fixes the bug discussed in
> https://www.mail-archive.com/kvm@vger.kernel.org/msg109813.html
> 
> This patch uses a new field named irr_delivered to record the
> delivery status of edge-triggered interrupts, and clears the
> delivered interrupts in kvm_get_ioapic. So it has the same effect
> of commit 0bc830b05c667218d703f2026ec866c49df974fc
> ("KVM: ioapic: clear IRR for edge-triggered interrupts at delivery")
> while avoids the bug of Windows guests.
> 
> Signed-off-by: Wincy Van <fanwenyi0529@...il.com>
> ---
>  arch/x86/kvm/ioapic.c |    7 ++++++-
>  arch/x86/kvm/ioapic.h |    1 +
>  2 files changed, 7 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/kvm/ioapic.c b/arch/x86/kvm/ioapic.c
> index b1947e0..a2e9d96 100644
> --- a/arch/x86/kvm/ioapic.c
> +++ b/arch/x86/kvm/ioapic.c
> @@ -206,6 +206,8 @@ static int ioapic_set_irq(struct kvm_ioapic *ioapic, unsigned int irq,
>  
>  	old_irr = ioapic->irr;
>  	ioapic->irr |= mask;
> +	if (edge)
> +		ioapic->irr_delivered &= ~mask;
>  	if ((edge && old_irr == ioapic->irr) ||
>  	    (!edge && entry.fields.remote_irr)) {
>  		ret = 0;
> @@ -349,7 +351,7 @@ static int ioapic_service(struct kvm_ioapic *ioapic, int irq, bool line_status)
>  	irqe.shorthand = 0;
>  
>  	if (irqe.trig_mode == IOAPIC_EDGE_TRIG)
> -		ioapic->irr &= ~(1 << irq);
> +		ioapic->irr_delivered |= 1 << irq;
>  
>  	if (irq == RTC_GSI && line_status) {
>  		/*
> @@ -597,6 +599,7 @@ static void kvm_ioapic_reset(struct kvm_ioapic *ioapic)
>  	ioapic->base_address = IOAPIC_DEFAULT_BASE_ADDRESS;
>  	ioapic->ioregsel = 0;
>  	ioapic->irr = 0;
> +	ioapic->irr_delivered = 0;
>  	ioapic->id = 0;
>  	memset(ioapic->irq_eoi, 0x00, IOAPIC_NUM_PINS);
>  	rtc_irq_eoi_tracking_reset(ioapic);
> @@ -654,6 +657,7 @@ int kvm_get_ioapic(struct kvm *kvm, struct kvm_ioapic_state *state)
>  
>  	spin_lock(&ioapic->lock);
>  	memcpy(state, ioapic, sizeof(struct kvm_ioapic_state));
> +	state->irr &= ~ioapic->irr_delivered;
>  	spin_unlock(&ioapic->lock);
>  	return 0;
>  }
> @@ -667,6 +671,7 @@ int kvm_set_ioapic(struct kvm *kvm, struct kvm_ioapic_state *state)
>  	spin_lock(&ioapic->lock);
>  	memcpy(ioapic, state, sizeof(struct kvm_ioapic_state));
>  	ioapic->irr = 0;
> +	ioapic->irr_delivered = 0;
>  	update_handled_vectors(ioapic);
>  	kvm_vcpu_request_scan_ioapic(kvm);
>  	kvm_ioapic_inject_all(ioapic, state->irr);
> diff --git a/arch/x86/kvm/ioapic.h b/arch/x86/kvm/ioapic.h
> index 3c91955..a5cdfc0 100644
> --- a/arch/x86/kvm/ioapic.h
> +++ b/arch/x86/kvm/ioapic.h
> @@ -77,6 +77,7 @@ struct kvm_ioapic {
>  	struct rtc_status rtc_status;
>  	struct delayed_work eoi_inject;
>  	u32 irq_eoi[IOAPIC_NUM_PINS];
> +	u32 irr_delivered;
>  };
>  
>  #ifdef DEBUG
> 

Does this introduce a state which requires save/restore on migration? If
so, then you need to extend the existing interface - in a
backward-compatible way. If not, please leave a remark on the reason.

Jan



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