[PATCH v3 5/5] KVM: PPC: Document KVM_PPC_GET_COMPAT_CAPS ioctl
From: Amit Machhiwal <hidden>
Date: 2026-05-22 15:28:34
Also in:
kvm, linuxppc-dev, lkml
Subsystem:
documentation, kernel virtual machine (kvm), the rest · Maintainers:
Jonathan Corbet, Paolo Bonzini, Linus Torvalds
Add documentation for the KVM_PPC_GET_COMPAT_CAPS ioctl to the KVM API documentation. The ioctl exposes host processor compatibility modes supported for nested KVM guests on PowerPC systems. Reported-by: kernel test robot <redacted> Closes: https://lore.kernel.org/oe-kbuild-all/202605140717.W1StD3Ke-lkp@intel.com/ (local) Tested-by: Anushree Mathur <redacted> Signed-off-by: Amit Machhiwal <redacted> --- Documentation/virt/kvm/api.rst | 35 ++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+)
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 52bbbb553ce1..d11e054e6665 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst@@ -6555,6 +6555,41 @@ KVM_S390_KEYOP_SSKE .. _kvm_run: +4.145 KVM_PPC_GET_COMPAT_CAPS +----------------------------- +:Capability: KVM_CAP_PPC_COMPAT_CAPS +:Architectures: powerpc +:Type: vm ioctl +:Parameters: struct kvm_ppc_compat_caps (out) +:Returns: + 0 on successful completion, + -EFAULT if ``struct kvm_ppc_compat_caps`` cannot be written + +IBM POWER system server-based processors provide a compatibility mode feature +where an Nth generation processor can operate in modes consistent with earlier +generations such as (N-1) and (N-2). + +This ioctl provides userspace with information about the CPU compatibility modes +supported by the current host processor for booting the nested KVM guests on +PowerNV (KVM nested APIv1) and PowerVM (KVM nested APIv2) platforms. + +:: + + struct kvm_ppc_compat_caps { + __u64 flags; /* Reserved for future use */ + __u64 compat_capabilities; /* Capabilities supported by the host */ + }; + +The ``compat_capabilities`` bit field describes the processor compatibility +modes supported by the host. For example, the following bits indicate support +for specific processor modes. + +:: + + H_GUEST_CAP_POWER9 (bit 1): KVM guests can run in Power9 processor mode + H_GUEST_CAP_POWER10 (bit 2): KVM guests can run in Power10 processor mode + H_GUEST_CAP_POWER11 (bit 3): KVM guests can run in Power11 processor mode + 5. The kvm_run structure ========================
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2.50.1 (Apple Git-155)