Re: [PATCH v3 02/11] KVM: x86: Change __kvm_apic_update_irr() to also return if max IRR updated

[Quan Xu <quan.xu0@xxxxxxxxx>]

On 2017/12/25 00:12, Liran Alon wrote:
> This commit doesn't change semantics.
> It is done as a preparation for future commits.
>
> Signed-off-by: Liran Alon <liran.alon@xxxxxxxxxx>
> Reviewed-by: Nikita Leshenko <nikita.leshchenko@xxxxxxxxxx>
> Reviewed-by: Liam Merwick <liam.merwick@xxxxxxxxxx>
> Signed-off-by: Liam Merwick <liam.merwick@xxxxxxxxxx>
> ---
>   arch/x86/kvm/lapic.c | 23 ++++++++++++++++-------
>   arch/x86/kvm/lapic.h |  4 ++--
>   arch/x86/kvm/vmx.c   |  5 +++--
>   3 files changed, 21 insertions(+), 11 deletions(-)
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 0928608750e3..924ac8ce9d50 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -364,32 +364,41 @@ static u8 count_vectors(void *bitmap)
>   	return count;
>   }
>   
> -int __kvm_apic_update_irr(u32 *pir, void *regs)
> +bool __kvm_apic_update_irr(u32 *pir, void *regs, int *max_irr)
>   {
>   	u32 i, vec;
> -	u32 pir_val, irr_val;
> -	int max_irr = -1;
> +	u32 pir_val, irr_val, prev_irr_val;
> +	int max_updated_irr;
> +
> +	max_updated_irr = -1;
  combine this 2 lines..

> +	*max_irr = -1;
>   
>   	for (i = vec = 0; i <= 7; i++, vec += 32) {
>   		pir_val = READ_ONCE(pir[i]);
>   		irr_val = *((u32 *)(regs + APIC_IRR + i * 0x10));
>   		if (pir_val) {
> +			prev_irr_val = irr_val;
>   			irr_val |= xchg(&pir[i], 0);
>   			*((u32 *)(regs + APIC_IRR + i * 0x10)) = irr_val;
> +			if (prev_irr_val != irr_val) {
> +				max_updated_irr =
> +					__fls(irr_val ^ prev_irr_val) + vec;
> +			}
>   		}
  perhaps, we could use some macros, instead of 7, 32, 0x10 ..

>   		if (irr_val)
> -			max_irr = __fls(irr_val) + vec;
> +			*max_irr = __fls(irr_val) + vec;
>   	}
>   
> -	return max_irr;
> +	return ((max_updated_irr != -1) &&
> +		(max_updated_irr == *max_irr));
>   }
>   EXPORT_SYMBOL_GPL(__kvm_apic_update_irr);
>   
> -int kvm_apic_update_irr(struct kvm_vcpu *vcpu, u32 *pir)
> +bool kvm_apic_update_irr(struct kvm_vcpu *vcpu, u32 *pir, int *max_irr)
>   {
>   	struct kvm_lapic *apic = vcpu->arch.apic;
>   
> -	return __kvm_apic_update_irr(pir, apic->regs);
> +	return __kvm_apic_update_irr(pir, apic->regs, max_irr);
>   }
>   EXPORT_SYMBOL_GPL(kvm_apic_update_irr);
>   
> diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
> index 4b9935a38347..56c36014f7b7 100644
> --- a/arch/x86/kvm/lapic.h
> +++ b/arch/x86/kvm/lapic.h
> @@ -75,8 +75,8 @@ int kvm_lapic_reg_read(struct kvm_lapic *apic, u32 offset, int len,
>   bool kvm_apic_match_dest(struct kvm_vcpu *vcpu, struct kvm_lapic *source,
>   			   int short_hand, unsigned int dest, int dest_mode);
>   
> -int __kvm_apic_update_irr(u32 *pir, void *regs);
> -int kvm_apic_update_irr(struct kvm_vcpu *vcpu, u32 *pir);
> +bool __kvm_apic_update_irr(u32 *pir, void *regs, int *max_irr);
> +bool kvm_apic_update_irr(struct kvm_vcpu *vcpu, u32 *pir, int *max_irr);
>   void kvm_apic_update_ppr(struct kvm_vcpu *vcpu);
>   int kvm_apic_set_irq(struct kvm_vcpu *vcpu, struct kvm_lapic_irq *irq,
>   		     struct dest_map *dest_map);
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 8eba631c4dbd..325608a1ed65 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -5062,7 +5062,8 @@ static void vmx_complete_nested_posted_interrupt(struct kvm_vcpu *vcpu)
>   	max_irr = find_last_bit((unsigned long *)vmx->nested.pi_desc->pir, 256);
>   	if (max_irr != 256) {
>   		vapic_page = kmap(vmx->nested.virtual_apic_page);
> -		__kvm_apic_update_irr(vmx->nested.pi_desc->pir, vapic_page);
> +		__kvm_apic_update_irr(vmx->nested.pi_desc->pir,
> +			vapic_page, &max_irr);
>   		kunmap(vmx->nested.virtual_apic_page);
>   
>   		status = vmcs_read16(GUEST_INTR_STATUS);
> @@ -9040,7 +9041,7 @@ static int vmx_sync_pir_to_irr(struct kvm_vcpu *vcpu)
>   		 * But on x86 this is just a compiler barrier anyway.
>   		 */
>   		smp_mb__after_atomic();
> -		max_irr = kvm_apic_update_irr(vcpu, vmx->pi_desc.pir);
> +		kvm_apic_update_irr(vcpu, vmx->pi_desc.pir, &max_irr);
>   	} else {
>   		max_irr = kvm_lapic_find_highest_irr(vcpu);
>   	}
Reviewed-by: Quan Xu <quan.xu0@xxxxxxxxx>


Quan
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