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KVM: x86: Document that KVM_CREATE_IRQCHIP must precede vCPU creation

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The kernel rejects KVM_CREATE_IRQCHIP with -EINVAL if any vCPUs have
already been created, but the API documentation does not mention this
constraint.  Add a note.

Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Link: https://patch.msgid.link/20260708133856.302151-2-twiederh@redhat.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Tim Wiederhake 2026-07-08 15:38:54 +02:00 committed by Sean Christopherson
parent db3a46e200
commit d82d77c643
1 changed files with 2 additions and 1 deletions
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Documentation/virt/kvm/api.rst
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@ -856,7 +856,8 @@ Writes the floating point state to the vcpu.
Creates an interrupt controller model in the kernel.
On x86, creates a virtual ioapic, a virtual PIC (two PICs, nested), and sets up
future vcpus to have a local APIC. IRQ routing for GSIs 0-15 is set to both
PIC and IOAPIC; GSI 16-23 only go to the IOAPIC.
PIC and IOAPIC; GSI 16-23 only go to the IOAPIC. This ioctl can only be
called before creating any vcpus.
On arm64, a GICv2 is created. Any other GIC versions require the usage of
KVM_CREATE_DEVICE, which also supports creating a GICv2. Using
KVM_CREATE_DEVICE is preferred over KVM_CREATE_IRQCHIP for GICv2.