KVM: PPC: Book3S: Enable XIVE native capability only if OPAL has required functions

There are some POWER9 machines where the OPAL firmware does not support
the OPAL_XIVE_GET_QUEUE_STATE and OPAL_XIVE_SET_QUEUE_STATE calls.
The impact of this is that a guest using XIVE natively will not be able
to be migrated successfully.  On the source side, the get_attr operation
on the KVM native device for the KVM_DEV_XIVE_GRP_EQ_CONFIG attribute
will fail; on the destination side, the set_attr operation for the same
attribute will fail.

This adds tests for the existence of the OPAL get/set queue state
functions, and if they are not supported, the XIVE-native KVM device
is not created and the KVM_CAP_PPC_IRQ_XIVE capability returns false.
Userspace can then either provide a software emulation of XIVE, or
else tell the guest that it does not have a XIVE controller available
to it.

Cc: stable@vger.kernel.org # v5.2+
Fixes: 3fab2d1058 ("KVM: PPC: Book3S HV: XIVE: Activate XIVE exploitation mode")
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

arch/powerpc/include/asm/kvm_ppc.h

@@ -598,6 +598,7 @@ extern int kvmppc_xive_native_get_vp(struct kvm_vcpu *vcpu,
 				     union kvmppc_one_reg *val);
 extern int kvmppc_xive_native_set_vp(struct kvm_vcpu *vcpu,
 				     union kvmppc_one_reg *val);
+extern bool kvmppc_xive_native_supported(void);
 
 #else
 static inline int kvmppc_xive_set_xive(struct kvm *kvm, u32 irq, u32 server,

arch/powerpc/include/asm/xive.h

@@ -135,6 +135,7 @@ extern int xive_native_get_queue_state(u32 vp_id, uint32_t prio, u32 *qtoggle,
 extern int xive_native_set_queue_state(u32 vp_id, uint32_t prio, u32 qtoggle,
 				       u32 qindex);
 extern int xive_native_get_vp_state(u32 vp_id, u64 *out_state);
+extern bool xive_native_has_queue_state_support(void);
 
 #else