linux-kernel - Re: [RFC v2 02/12] KVM: arm/arm64: Document KVM_VGIC_V3_ADDR_TYPE_REDIST

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Date:   Mon, 9 Apr 2018 23:38:52 +0200
From:   Christoffer Dall <cdall@...nel.org>
To:     Eric Auger <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, peter.maydell@...aro.org,
        andre.przywara@....com, drjones@...hat.com, wei@...hat.com
Subject: Re: [RFC v2 02/12] KVM: arm/arm64: Document
 KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION

Hi Eric,

On Tue, Mar 27, 2018 at 04:04:06PM +0200, Eric Auger wrote:
> We introduce a new KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION attribute in
> KVM_DEV_ARM_VGIC_GRP_ADDR group. It allows userspace to provide the
> base address and size of a redistributor region
> 
> Compared to KVM_VGIC_V3_ADDR_TYPE_REDIST, this new attribute allows
> to declare several separate redistributor regions.
> 
> So the whole redist space does not need to be contiguous anymore.
> 
> Signed-off-by: Eric Auger <eric.auger@...hat.com>
> ---
>  Documentation/virtual/kvm/devices/arm-vgic-v3.txt | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/Documentation/virtual/kvm/devices/arm-vgic-v3.txt b/Documentation/virtual/kvm/devices/arm-vgic-v3.txt
> index 9293b45..0ded904 100644
> --- a/Documentation/virtual/kvm/devices/arm-vgic-v3.txt
> +++ b/Documentation/virtual/kvm/devices/arm-vgic-v3.txt
> @@ -27,6 +27,24 @@ 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
> +      - flags: reserved for future use, currently 0
> +      - base field encodes bits [51:16] of the guest physical base address
> +        of the first redistributor in the region. There are two 64K pages
> +        for each VCPU and all of the redistributor pages are contiguous

should this be two 64K pages for the number of redistributors in this
region as specified by count ?

> +        within the redistributor region.
> +      - count encodes the number of redistributors in the region.

I assume it's implied that the user must register a total number of
redistributors across all the regions that matches the number of vcpus,
and that otherwise something bad happens?

> +      Only valid for KVM_DEV_TYPE_ARM_VGIC_V3.
> +
> +  It is invalid to mix calls with KVM_VGIC_V3_ADDR_TYPE_REDIST and
> +  KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION attributes. When attempted an
> +  -EINVAL error is returned.
> +
>    Errors:
>      -E2BIG:  Address outside of addressable IPA range
>      -EINVAL: Incorrectly aligned address
> -- 
> 2.5.5
> 

Thanks,
-Christoffer