Re: [PATCH RFC untested] kvm_set_irq: report coalesced for clear

[Gleb Natapov <gleb@redhat.com>]

On Thu, Jul 19, 2012 at 01:11:53AM +0300, Michael S. Tsirkin wrote:
> This creates a way to detect when kvm_set_irq(...,0) was run
> twice with the same source id by returning 0 in this case.
> 
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
> 
> This is on top of my bugfix patch.  Uncompiled and untested.  Alex, I
> think something like this patch will make it possible for you to simply
> do
> 	if (kvm_set_irq(...., 0))
> 		eventfd_signal()
> 
Why caller can't track line state?

> without need for further tricks.
> 
>  arch/x86/include/asm/kvm_host.h |  9 ++++-----
>  arch/x86/kvm/i8259.c            | 11 +++++++----
>  virt/kvm/ioapic.c               | 17 ++++++++++-------
>  3 files changed, 21 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index fe6e9f1..6f5ed0a 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -802,16 +802,15 @@ int kvm_read_guest_page_mmu(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
>  void kvm_propagate_fault(struct kvm_vcpu *vcpu, struct x86_exception *fault);
>  bool kvm_require_cpl(struct kvm_vcpu *vcpu, int required_cpl);
>  
> -static inline int kvm_irq_line_state(unsigned long *irq_state,
> +/* Tweak line state. Return true if state was changed. */
> +static inline bool kvm_irq_line_state(unsigned long *irq_state,
>  				     int irq_source_id, int level)
>  {
>  	/* Logical OR for level trig interrupt */
>  	if (level)
> -		__set_bit(irq_source_id, irq_state);
> +		return !__test_and_set_bit(irq_source_id, irq_state);
>  	else
> -		__clear_bit(irq_source_id, irq_state);
> -
> -	return !!(*irq_state);
> +		return __test_and_clear_bit(irq_source_id, irq_state);
>  }
>  
>  int kvm_pic_set_irq(struct kvm_pic *pic, int irq, int irq_source_id, int level);
> diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
> index 95b504b..44e3635 100644
> --- a/arch/x86/kvm/i8259.c
> +++ b/arch/x86/kvm/i8259.c
> @@ -190,12 +190,15 @@ void kvm_pic_update_irq(struct kvm_pic *s)
>  
>  int kvm_pic_set_irq(struct kvm_pic *s, int irq, int src_id, int l)
>  {
> -	int ret = -1;
> -	int level;
> +	int ret, level;
>  
>  	pic_lock(s);
> -	if (irq >= 0 && irq < PIC_NUM_PINS) {
> -		level = kvm_irq_line_state(&s->irq_states[irq], src_id, l);
> +	if (irq < 0 || irq >= PIC_NUM_PINS) {
> +		ret = -1;
> +	} else if (!kvm_irq_line_state(&s->irq_states[irq], src_id, l)) {
> +		ret = 0;
> +	} else {
> +		level = !!s->irq_states[irq];
>  		ret = pic_set_irq1(&s->pics[irq >> 3], irq & 7, level);
>  		pic_update_irq(s);
>  		trace_kvm_pic_set_irq(irq >> 3, irq & 7, s->pics[irq >> 3].elcr,
> diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
> index 268b332..edc9445 100644
> --- a/virt/kvm/ioapic.c
> +++ b/virt/kvm/ioapic.c
> @@ -196,18 +196,21 @@ int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int src_id, int l)
>  	u32 old_irr;
>  	u32 mask = 1 << irq;
>  	union kvm_ioapic_redirect_entry entry;
> -	int ret = 1;
> -	int level;
> +	int ret, level;
>  
>  	spin_lock(&ioapic->lock);
>  	old_irr = ioapic->irr;
> -	if (irq >= 0 && irq < IOAPIC_NUM_PINS) {
> +	if (irq < 0 || irq >= IOAPIC_NUM_PINS) {
> +		ret = -1;
> +	} else if (!kvm_irq_line_state(&ioapic->irq_states[irq], src_id, l)) {
> +		ret = 0;
> +	} else {
>  		entry = ioapic->redirtbl[irq];
> -		level = kvm_irq_line_state(&ioapic->irq_states[irq], src_id, l);
> -		level ^= entry.fields.polarity;
> -		if (!level)
> +		level = (!!ioapic->irq_states[irq]) ^ entry.fields.polarity;
> +		if (!level) {
>  			ioapic->irr &= ~mask;
> -		else {
> +			ret = 1;
> +		} else {
>  			int edge = (entry.fields.trig_mode == IOAPIC_EDGE_TRIG);
>  			ioapic->irr |= mask;
>  			if ((edge && old_irr != ioapic->irr) ||
> -- 
> MST

--
			Gleb.