Re: [RFC] dom0less vcpu affinity bindings

[Julien Grall <julien@xxxxxxx>]

Hi Stefano,

On 11/02/2025 01:56, Stefano Stabellini wrote:
> We have received requests to introduce Dom0less vCPU affinity bindings
> to allow configuring which pCPUs a given vCPU is allowed to run on.
>
> After considering different approaches, I am thinking of using the
> following binding format:
>
>      vcpu0 {
>             compatible = "xen,vcpu-affinity"; // compatible string
>             id = <0>;  // vcpu id
>             hard-affinity = "1,4-7"; // pcpu ranges
This would be CPU logical ID, right? This is a value assigned by Xen 
based on how pCPU are brought up. So in theory it could change between 
Xen version as the order is not guaranteed. I know this is what the 
toolstack is currently using.
However, as we define a new binding, I wonder whether it would be better 
to instead have a phandle to the CPU device-tree node or just plain 
MPIDRs? This would guarantee that the vCPU will always land on a given 
pCPU (this could be important when taking into account the cache topology).
Cheers,

--
Julien Grall