On Tue, 14 Jul 2026 23:24:32 +0530, Amit Machhiwal wrote:
> On IBM POWER systems, newer processor generations can operate in
> compatibility modes corresponding to earlier generations. This becomes
> relevant for nested virtualization, where nested KVM guests may need to
> run with a specific processor compatibility level.
>
> Currently, when running a nested KVM guest (L2) inside a Power11 pSeries
> logical partition (L1) booted in Power10 compatibility mode, the guest
> fails to boot while setting 'arch_compat'. This happens because the CPU
> class is derived from the hardware PVR (via mfspr()), which reflects the
> physical processor generation (Power11), rather than the effective
> compatibility mode (Power10).
>
> [...]
Applied to powerpc/next.
[1/1] KVM: PPC: Book3S HV: Validate arch_compat against host compatibility mode
https://git.kernel.org/powerpc/c/884ea0283f4effac97ee8f451464a7d1be480d7c
cheers
