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diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 2b52eb77e29c..1f8625b7646a 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -1000,6 +1000,10 @@ blobs in userspace. When the guest writes the MSR, kvm copies one
page of a blob (32- or 64-bit, depending on the vcpu mode) to guest
memory.
+The MSR index must be in the range [0x40000000, 0x4fffffff], i.e. must reside
+in the range that is unofficially reserved for use by hypervisors. The min/max
+values are enumerated via KVM_XEN_MSR_MIN_INDEX and KVM_XEN_MSR_MAX_INDEX.
+
::
struct kvm_xen_hvm_config {
@@ -8258,6 +8262,24 @@ KVM exits with the register state of either the L1 or L2 guest
depending on which executed at the time of an exit. Userspace must
take care to differentiate between these cases.
+7.37 KVM_CAP_ARM_WRITABLE_IMP_ID_REGS
+-------------------------------------
+
+:Architectures: arm64
+:Target: VM
+:Parameters: None
+:Returns: 0 on success, -EINVAL if vCPUs have been created before enabling this
+ capability.
+
+This capability changes the behavior of the registers that identify a PE
+implementation of the Arm architecture: MIDR_EL1, REVIDR_EL1, and AIDR_EL1.
+By default, these registers are visible to userspace but treated as invariant.
+
+When this capability is enabled, KVM allows userspace to change the
+aforementioned registers before the first KVM_RUN. These registers are VM
+scoped, meaning that the same set of values are presented on all vCPUs in a
+given VM.
+
8. Other capabilities.
======================