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

Auger Eric
2018-04-26T07:47:00Z

Hi Christoffer,
On 04/24/2018 11:07 PM, Christoffer Dall wrote:
> 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@redhat.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 ?
We always find the first empty 2x64kB slot within the region (stride
between redistributors = 0). Regions are filled in the index order. The
only hole that can exist is at the end of the region if its size is not
multiple of 2x64kB.
>
> I assume there is some mapping between the regions and the VCPUs'
> redistributors, so perhaps the wording in this comment can be more
> precise.
changed into:
"
A redistributor regions maps n redistributors, n = region size / (2 x 64kB).
Stride between redistributors is 0 and regions are filled in the index
order.
"

>
>> + *
>> + * 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@arm.com>
Thanks

Eric
>