Re: [PATCH v3 07/12] KVM: arm/arm64: Adapt vgic_v3_check_base to multiple rdist regions

Auger Eric
2018-04-26T08:29:35Z

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.

Thanks

Eric
>
>>
>> Signed-off-by: Eric Auger <eric.auger@redhat.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
>