[PATCH] KVM: x86: Complain about an attempt to change the APIC base address

[Jim Mattson <jmattson@google.com>]

KVM does not support changing the APIC's base address. Prior to commit
3743c2f02517 ("KVM: x86: inhibit APICv/AVIC on changes to APIC ID or
APIC base"), it emitted a rate-limited warning about this. Now, it's
just silently broken.

Use vcpu_unimpl() to complain about this unsupported operation. Even a
rate-limited error message is better than complete silence.

Fixes: 3743c2f02517 ("KVM: x86: inhibit APICv/AVIC on changes to APIC ID or APIC base")
Signed-off-by: Jim Mattson <jmattson@google.com>
---
 arch/x86/kvm/lapic.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index acd7d48100a1..5284dddab337 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2583,6 +2583,8 @@ void kvm_lapic_set_base(struct kvm_vcpu *vcpu, u64 value)
 
 	if ((value & MSR_IA32_APICBASE_ENABLE) &&
 	     apic->base_address != APIC_DEFAULT_PHYS_BASE) {
+		vcpu_unimpl(vcpu, "APIC base %#llx is not %#llx",
+			    apic->base_address, APIC_DEFAULT_PHYS_BASE);
 		kvm_set_apicv_inhibit(apic->vcpu->kvm,
 				      APICV_INHIBIT_REASON_APIC_BASE_MODIFIED);
 	}
-- 
2.45.2.741.gdbec12cfda-goog