KVM: PPC: Book3S HV: Allow creating max number of VCPUs on POWER9

Commit 1e175d2e ("KVM: PPC: Book3S HV: Pack VCORE IDs to access full
VCPU ID space", 2018-07-25) allowed use of VCPU IDs up to
KVM_MAX_VCPU_ID on POWER9 in all guest SMT modes and guest emulated
hardware SMT modes.  However, with the current definition of
KVM_MAX_VCPU_ID, a guest SMT mode of 1 and an emulated SMT mode of 8,
it is only possible to create KVM_MAX_VCPUS / 2 VCPUS, because
threads_per_subcore is 4 on POWER9 CPUs.  (Using an emulated SMT mode
of 8 is useful when migrating VMs to or from POWER8 hosts.)

This increases KVM_MAX_VCPU_ID to 8 * KVM_MAX_VCPUS when HV KVM is
configured in, so that a full complement of KVM_MAX_VCPUS VCPUs can
be created on POWER9 in all guest SMT modes and emulated hardware
SMT modes.
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

arch/powerpc/include/asm/kvm_host.h

@@ -42,7 +42,14 @@
 #define KVM_USER_MEM_SLOTS	512
 
 #include <asm/cputhreads.h>
-#define KVM_MAX_VCPU_ID                (threads_per_subcore * KVM_MAX_VCORES)
+
+#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
+#include <asm/kvm_book3s_asm.h>		/* for MAX_SMT_THREADS */
+#define KVM_MAX_VCPU_ID		(MAX_SMT_THREADS * KVM_MAX_VCORES)
+
+#else
+#define KVM_MAX_VCPU_ID		KVM_MAX_VCPUS
+#endif /* CONFIG_KVM_BOOK3S_HV_POSSIBLE */
 
 #define __KVM_HAVE_ARCH_INTC_INITIALIZED