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

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

[Wincy Van]

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@gmail.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
-- 
1.7.1

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

[Jan Kiszka]

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

[Wincy Van]

2014-12-24 23:29 GMT+08:00 Jan Kiszka <jan.kiszka@web.de>:
> 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@gmail.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.
>

No, we do not need to save/restore irr_delivered.

First of all, irr_delivered affects irr only when saving ioapic's
state, it does not affect any of the ioapic's logic.

Then, let's see what will happen if we do not save/restore that field :

1. If irr_delivered is 0 before saving, it is no difference at all.
2. If a bit of irr_delivered is 1 before saving, since irr_delivered
only affects migration,
    we should check that if the 2nd+ migration is OK.
    There are 3 possibilities on the first destination :
    (1) The edge-triggered IRQ is masked, that bit will be cleared, it
is no difference to do 2nd migration.
    (2) The edge-triggered IRQ is raised and not masked, that bit will
be set again, it is no difference to do 2nd migration.
    (3) The edge-triggered IRQ is lowered, and the corresponding bit
of irr is cleared,
          the result of "state->irr &= ~ioapic->irr_delivered" in
kvm_get_ioapic is not affected by irr_delivered.

So it is OK to migrate with a stateless irr_delivered.


Thanks,

Wincy




> Jan
>
>

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

[Wincy Van]

Ping..

Hi, Paolo, could you please have a look at this patch ?


Thanks,

Wincy

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

[Marcelo Tosatti]

On Wed, Dec 24, 2014 at 11:14:29AM +0800, 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@gmail.com>

Applied, thanks.