Re: [PATCH v2 8/9] KVM: arm/arm64: vgic-its: Check the LPI translation cache on MSI injection

[Auger Eric <eric.auger@redhat.com>]

Hi Marc,

On 6/11/19 7:03 PM, Marc Zyngier wrote:
> When performing an MSI injection, let's first check if the translation
> is already in the cache. If so, let's inject it quickly without
> going through the whole translation process.
> 
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
>  virt/kvm/arm/vgic/vgic-its.c | 36 ++++++++++++++++++++++++++++++++++++
>  virt/kvm/arm/vgic/vgic.h     |  1 +
>  2 files changed, 37 insertions(+)
> 
> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
> index 62932458476a..83d80ec33473 100644
> --- a/virt/kvm/arm/vgic/vgic-its.c
> +++ b/virt/kvm/arm/vgic/vgic-its.c
> @@ -577,6 +577,20 @@ static struct vgic_irq *__vgic_its_check_cache(struct vgic_dist *dist,
>  	return irq;
>  }
>  
> +static struct vgic_irq *vgic_its_check_cache(struct kvm *kvm, phys_addr_t db,
> +					     u32 devid, u32 eventid)
> +{
> +	struct vgic_dist *dist = &kvm->arch.vgic;
> +	struct vgic_irq *irq;
> +	unsigned long flags;
> +
> +	raw_spin_lock_irqsave(&dist->lpi_list_lock, flags);
> +	irq = __vgic_its_check_cache(dist, db, devid, eventid);
> +	raw_spin_unlock_irqrestore(&dist->lpi_list_lock, flags);
> +
> +	return irq;
> +}
> +
>  static void vgic_its_cache_translation(struct kvm *kvm, struct vgic_its *its,
>  				       u32 devid, u32 eventid,
>  				       struct vgic_irq *irq)
> @@ -736,6 +750,25 @@ static int vgic_its_trigger_msi(struct kvm *kvm, struct vgic_its *its,
>  	return 0;
>  }
>  
> +int vgic_its_inject_cached_translation(struct kvm *kvm, struct kvm_msi *msi)
> +{
> +	struct vgic_irq *irq;
> +	unsigned long flags;
> +	phys_addr_t db;
> +
> +	db = (u64)msi->address_hi << 32 | msi->address_lo;
> +	irq = vgic_its_check_cache(kvm, db, msi->devid, msi->data);

I think we miss a check of its->enabled. This is currently done in
vgic_its_resolve_lpi() but now likely to be bypassed.

Doing that in this function is needed for next patch I think.

Thanks

Eric
> +
> +	if (!irq)
> +		return -1;
> +
> +	raw_spin_lock_irqsave(&irq->irq_lock, flags);
> +	irq->pending_latch = true;
> +	vgic_queue_irq_unlock(kvm, irq, flags);
> +
> +	return 0;
> +}
> +
>  /*
>   * Queries the KVM IO bus framework to get the ITS pointer from the given
>   * doorbell address.
> @@ -747,6 +780,9 @@ int vgic_its_inject_msi(struct kvm *kvm, struct kvm_msi *msi)
>  	struct vgic_its *its;
>  	int ret;
>  
> +	if (!vgic_its_inject_cached_translation(kvm, msi))
> +		return 1;
> +
>  	its = vgic_msi_to_its(kvm, msi);
>  	if (IS_ERR(its))
>  		return PTR_ERR(its);
> diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
> index 072f810dc441..ad6eba1e2beb 100644
> --- a/virt/kvm/arm/vgic/vgic.h
> +++ b/virt/kvm/arm/vgic/vgic.h
> @@ -317,6 +317,7 @@ int vgic_copy_lpi_list(struct kvm *kvm, struct kvm_vcpu *vcpu, u32 **intid_ptr);
>  int vgic_its_resolve_lpi(struct kvm *kvm, struct vgic_its *its,
>  			 u32 devid, u32 eventid, struct vgic_irq **irq);
>  struct vgic_its *vgic_msi_to_its(struct kvm *kvm, struct kvm_msi *msi);
> +int vgic_its_inject_cached_translation(struct kvm *kvm, struct kvm_msi *msi);
>  void vgic_lpi_translation_cache_init(struct kvm *kvm);
>  void vgic_lpi_translation_cache_destroy(struct kvm *kvm);
>  void vgic_its_invalidate_cache(struct kvm *kvm);
> 

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