linux-kernel - Re: [PATCH v3 04/12] KVM: arm/arm64: Helper to locate free rdist index

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Date:   Tue, 24 Apr 2018 23:07:04 +0200
From:   Christoffer Dall <christoffer.dall@....com>
To:     Eric Auger <eric.auger@...hat.com>
Cc:     eric.auger.pro@...il.com, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, kvmarm@...ts.cs.columbia.edu,
        marc.zyngier@....com, cdall@...nel.org, peter.maydell@...aro.org,
        andre.przywara@....com, drjones@...hat.com, wei@...hat.com
Subject: Re: [PATCH v3 04/12] KVM: arm/arm64: Helper to locate free rdist
 index

On Fri, Apr 13, 2018 at 10:20:50AM +0200, Eric Auger wrote:
> We introduce vgic_v3_rdist_free_slot to help identifying
> where we can place a new 2x64KB redistributor.
> 
> Signed-off-by: Eric Auger <eric.auger@...hat.com>
> ---
>  virt/kvm/arm/vgic/vgic-mmio-v3.c |  3 +--
>  virt/kvm/arm/vgic/vgic-v3.c      | 17 +++++++++++++++++
>  virt/kvm/arm/vgic/vgic.h         | 11 +++++++++++
>  3 files changed, 29 insertions(+), 2 deletions(-)
> 
> diff --git a/virt/kvm/arm/vgic/vgic-mmio-v3.c b/virt/kvm/arm/vgic/vgic-mmio-v3.c
> index d1aab18..49ca176 100644
> --- a/virt/kvm/arm/vgic/vgic-mmio-v3.c
> +++ b/virt/kvm/arm/vgic/vgic-mmio-v3.c
> @@ -593,8 +593,7 @@ int vgic_register_redist_iodev(struct kvm_vcpu *vcpu)
>  	 * function for all VCPUs when the base address is set.  Just return
>  	 * without doing any work for now.
>  	 */
> -	rdreg = list_first_entry(&vgic->rd_regions,
> -				 struct vgic_redist_region, list);
> +	rdreg = vgic_v3_rdist_free_slot(&vgic->rd_regions);
>  	if (!rdreg)
>  		return 0;
>  
> diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
> index 94de6cd..820012a 100644
> --- a/virt/kvm/arm/vgic/vgic-v3.c
> +++ b/virt/kvm/arm/vgic/vgic-v3.c
> @@ -444,6 +444,23 @@ bool vgic_v3_check_base(struct kvm *kvm)
>  	return false;
>  }
>  
> +/**
> + * vgic_v3_rdist_free_slot - Look up registered rdist regions and identify one
> + * which has free space to put a new rdist regions

Can this structure ever be sparse or do we always find the first empty
one, as we fill them consecutively ?

I assume there is some mapping between the regions and the VCPUs'
redistributors, so perhaps the wording in this comment can be more
precise.

> + *
> + * If any, return this redist region handle, otherwise returns NULL.
> + */
> +struct vgic_redist_region *vgic_v3_rdist_free_slot(struct list_head *rd_regions)
> +{
> +	struct vgic_redist_region *rdreg;
> +
> +	list_for_each_entry(rdreg, rd_regions, list) {
> +		if (!vgic_v3_redist_region_full(rdreg))
> +			return rdreg;
> +	}
> +	return NULL;
> +}
> +
>  int vgic_v3_map_resources(struct kvm *kvm)
>  {
>  	int ret = 0;
> diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
> index 830e815..fea32cb 100644
> --- a/virt/kvm/arm/vgic/vgic.h
> +++ b/virt/kvm/arm/vgic/vgic.h
> @@ -251,6 +251,17 @@ static inline int vgic_v3_max_apr_idx(struct kvm_vcpu *vcpu)
>  	}
>  }
>  
> +static inline bool
> +vgic_v3_redist_region_full(struct vgic_redist_region *region)
> +{
> +	if (!region->count)
> +		return false;
> +
> +	return (region->free_index >= region->count);
> +}
> +
> +struct vgic_redist_region *vgic_v3_rdist_free_slot(struct list_head *rdregs);
> +
>  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);
> -- 
> 2.5.5
> 

Asides from the above:

Reviewed-by: Christoffer Dall <christoffer.dall@....com>