Re: [PATCH v3 09/12] KVM: arm/arm64: Check all vcpu redistributors are set on map_resources

Auger Eric
2018-04-26T09:56:10Z

On 04/24/2018 11:08 PM, Christoffer Dall wrote:
> On Fri, Apr 13, 2018 at 10:20:55AM +0200, Eric Auger wrote:
>> On vcpu first run, we eventually know the actual number of vcpus.
>> This is a synchronization point to check all redistributors regions
>> were assigned.
>
> Isn't it the other way around? We want to check that all redistributors
> (one for every VCPU) has its base address set? (I don't suppose we care
> about unused redistributor regions).
Yes I meant "to check all redistributors were assigned"
>
>> On kvm_vgic_map_resources() we check both dist and
>> redist were set, eventually check potential base address inconsistencies.
>
> Do we need to check that again? Didn't we check that at
> creation/register time?
Yes we need to, to handle the case where the userspace does not provide
sufficient rdist region space

create 8 vcpus (no iodev registered)
define a redist region for 4 (4 iodevs registered)
start the vcpus
>
>>
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>> ---
>> virt/kvm/arm/vgic/vgic-v3.c | 19 ++++++++++++++-----
>> 1 file changed, 14 insertions(+), 5 deletions(-)
>>
>> diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
>> index b80f650..feabc24 100644
>> --- a/virt/kvm/arm/vgic/vgic-v3.c
>> +++ b/virt/kvm/arm/vgic/vgic-v3.c
>> @@ -484,16 +484,25 @@ struct vgic_redist_region *vgic_v3_rdist_region_from_index(struct kvm *kvm,
>>
>> int vgic_v3_map_resources(struct kvm *kvm)
>> {
>> - int ret = 0;
>> struct vgic_dist *dist = &kvm->arch.vgic;
>> - struct vgic_redist_region *rdreg =
>> - list_first_entry(&dist->rd_regions,
>> - struct vgic_redist_region, list);
>> + struct kvm_vcpu *vcpu;
>> + int ret = 0;
>> + int c;
>>
>> if (vgic_ready(kvm))
>> goto out;
>>
>> - if (IS_VGIC_ADDR_UNDEF(dist->vgic_dist_base) || !rdreg) {
>> + kvm_for_each_vcpu(c, vcpu, kvm) {
>> + struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
>> +
>> + if (IS_VGIC_ADDR_UNDEF(vgic_cpu->rd_iodev.base_addr)) {
>> + kvm_err("vcpu %d redistributor base not set\n", c);
>
> Shouldn't this be a kvm_debug instead? I think the user can just
> provoke this by failing to register enough redistributor regions.
yes indeed.
>
> I'm also wondering if we could check this on vgic_init time for gicv3,
> which should have a defined vgic init ordering requirement. That would
> make debugging it slightly easier to debug than "my machine isn't
> starting, and I get -ENXIO, and it can mean anything".

Well at vgic_init time, vcpus are frozen but dist and redist regions are
not forced to be set, hence the late check we do in map_resources, on
1st VCPU run. Not sure I get this one?

Thanks

Eric
>
>> + ret = -ENXIO;
>> + goto out;
>> + }
>> + }
>> +
>> + if (IS_VGIC_ADDR_UNDEF(dist->vgic_dist_base)) {
>> kvm_err("Need to set vgic distributor addresses first\n");
>> ret = -ENXIO;
>> goto out;
>> --
>> 2.5.5
>>
>
> Thanks,
> -Christoffer
>