Re: [PATCH v3 02/12] KVM: arm/arm64: Document KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION

Auger Eric
2018-04-24T20:34:57Z

Hi Christoffer, Peter,

On 04/24/2018 06:50 PM, Peter Maydell wrote:
> On 24 April 2018 at 17:46, Christoffer Dall <christoffer.dall@arm.com> wrote:
>> On Fri, Apr 13, 2018 at 10:20:48AM +0200, Eric Auger wrote:
>>> --- a/Documentation/virtual/kvm/devices/arm-vgic-v3.txt
>>> +++ b/Documentation/virtual/kvm/devices/arm-vgic-v3.txt
>>> @@ -27,9 +27,32 @@ Groups:
>>> VCPU and all of the redistributor pages are contiguous.
>>> Only valid for KVM_DEV_TYPE_ARM_VGIC_V3.
>>> This address needs to be 64K aligned.
>>> +
>>> + KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION (rw, 64-bit)
>>> + The attr field of kvm_device_attr encodes 3 values:
>>> + bits: | 63 .... 52 | 51 .... 16 | 15 - 12 |11 - 0
>>> + values: | count | base | flags | index
>>> + - index encodes the unique redistributor region index
>>
>> I'm not entirely sure I understand the purpose of the index field.
>> Isn't a redistributor region identified uniquely by its base address?
>
> You need a way to tell the difference beween:
> (1) redistributors for CPUs 0..63 at 0x40000000, redistributors
> for 64..127 at 0x80000000
> (2) redistributors for CPUs 0..63 at 0x80000000, redistributors
> for 64..127 at 0x40000000
>
> The index field tells you which order the redistributor
> regions go in.

Yes redistributors are filled in the index order. This matches DT
description
(Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.txt):

<0x0 0x2d000000 0 0x800000>, // GICR 1: CPUs 0-31
<0x0 0x2e000000 0 0x800000>; // GICR 2: CPUs 32-63

Thanks

Eric

>
> thanks
> -- PMM
>