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

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Message-ID: <20180426100615.GB19872@C02W217FHV2R.local>
Date:   Thu, 26 Apr 2018 12:06:15 +0200
From:   Christoffer Dall <christoffer.dall@....com>
To:     Auger Eric <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 Thu, Apr 26, 2018 at 10:29:35AM +0200, Auger Eric wrote:
> Hi Christoffer,
> On 04/24/2018 11:07 PM, Christoffer Dall wrote:
> > 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.
> I have merged this patch and vgic_v3_rd_region_size +
> vgic_v3_rdist_overlap and put it before this patch.
> 
> Also I reworked the commit message which was unclear I acknowledge.
> 
> With respect to using the adapted  vgic_v3_check_base() in
> vgic_v3_insert_redist_region(), it is less obvious to me.
> 
> In vgic_v3_insert_redist_region we do the checks *before* inserting the
> new rdist region in the list of redist regions. While
> vgic_v3_check_base() does the checks on already registered rdist and
> dist regions. So I would be tempted to leave
> vgic_v3_insert_redist_region() implementation as it is.
> 

ok, but do see my suggestion there to factor out the check, which should
make that function slightly easier to read.

Then perhaps you can use that function from vgic_v3_check_base to check
that each rdist doesn't overlap with the distributor?

Thanks,
-Christoffer