linux-kernel - Re: [PATCH v3 07/12] KVM: arm/arm64: Adapt vgic_v3_check

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Date:   Tue, 24 Apr 2018 23:07:48 +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 07/12] KVM: arm/arm64: Adapt vgic_v3_check_base to
 multiple rdist regions

On Fri, Apr 13, 2018 at 10:20:53AM +0200, Eric Auger wrote:
> We introduce a new helper to check there is no overlap between
> dist region (if set) and registered rdist regions. This both
> handles the case of legacy single rdist region (implicitly sized
> with the number of online vcpus) and the new case of multiple
> explicitly sized rdist regions.

I don't understand this change, really.  Is this just a cleanup, or
changing some functionality (why?).

I think this could have come with the introduction of
vgic_v3_rdist_overlap() before patch 6, and then patch 6 could have been
simplified (hopefully) to just call this "check that nothing in the
world ever collides withi itself" function.

> 
> Signed-off-by: Eric Auger <eric.auger@...hat.com>
> ---
>  virt/kvm/arm/vgic/vgic-v3.c | 26 +++++++++-----------------
>  1 file changed, 9 insertions(+), 17 deletions(-)
> 
> diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
> index dbcba5f..b80f650 100644
> --- a/virt/kvm/arm/vgic/vgic-v3.c
> +++ b/virt/kvm/arm/vgic/vgic-v3.c
> @@ -432,31 +432,23 @@ bool vgic_v3_rdist_overlap(struct kvm *kvm, gpa_t base, size_t size)
>  bool vgic_v3_check_base(struct kvm *kvm)
>  {
>  	struct vgic_dist *d = &kvm->arch.vgic;
> -	gpa_t redist_size = KVM_VGIC_V3_REDIST_SIZE;
> -	struct vgic_redist_region *rdreg =
> -		list_first_entry(&d->rd_regions,
> -				 struct vgic_redist_region, list);
> -
> -	redist_size *= atomic_read(&kvm->online_vcpus);
> +	struct vgic_redist_region *rdreg;
>  
>  	if (!IS_VGIC_ADDR_UNDEF(d->vgic_dist_base) &&
>  	    d->vgic_dist_base + KVM_VGIC_V3_DIST_SIZE < d->vgic_dist_base)
>  		return false;
>  
> -	if (rdreg && (rdreg->base + redist_size < rdreg->base))
> -		return false;
> +	list_for_each_entry(rdreg, &d->rd_regions, list) {
> +		if (rdreg->base + vgic_v3_rd_region_size(kvm, rdreg) <
> +			rdreg->base)
> +			return false;
> +	}
>  
> -	/* Both base addresses must be set to check if they overlap */
> -	if (IS_VGIC_ADDR_UNDEF(d->vgic_dist_base) || !rdreg)
> +	if (IS_VGIC_ADDR_UNDEF(d->vgic_dist_base))
>  		return true;
>  
> -	if (d->vgic_dist_base + KVM_VGIC_V3_DIST_SIZE <= rdreg->base)
> -		return true;
> -
> -	if (rdreg->base + redist_size <= d->vgic_dist_base)
> -		return true;
> -
> -	return false;
> +	return !vgic_v3_rdist_overlap(kvm, d->vgic_dist_base,
> +				      KVM_VGIC_V3_DIST_SIZE);
>  }
>  
>  /**
> -- 
> 2.5.5
> 
Otherwise this patch looks correct to me.

Thanks,
-Christoffer