KVM: PPC: Book3S PR: Allow KVM_PPC_CONFIGURE_V3_MMU to succeed

Currently, PR KVM does not implement the configure_mmu operation, and
so the KVM_PPC_CONFIGURE_V3_MMU ioctl always fails with an EINVAL
error.  This causes recent kernels to fail to boot as a PR KVM guest
on POWER9, since recent kernels booted in HPT mode do the
H_REGISTER_PROC_TBL hypercall, which causes userspace (QEMU) to do
KVM_PPC_CONFIGURE_V3_MMU, which fails.

This implements a minimal configure_mmu operation for PR KVM.  It
succeeds only if the MMU is being configured for HPT mode and no
process table is being registered.  This is enough to get recent
kernels to boot as a PR KVM guest.

Reviewed-by: Greg Kurz <groug@kaod.org>
Tested-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

arch/powerpc/kvm/book3s_pr.c

@@ -1687,6 +1687,17 @@ static int kvm_vm_ioctl_get_smmu_info_pr(struct kvm *kvm,
 
 	return 0;
 }
+
+static int kvm_configure_mmu_pr(struct kvm *kvm, struct kvm_ppc_mmuv3_cfg *cfg)
+{
+	if (!cpu_has_feature(CPU_FTR_ARCH_300))
+		return -ENODEV;
+	/* Require flags and process table base and size to all be zero. */
+	if (cfg->flags || cfg->process_table)
+		return -EINVAL;
+	return 0;
+}
+
 #else
 static int kvm_vm_ioctl_get_smmu_info_pr(struct kvm *kvm,
 					 struct kvm_ppc_smmu_info *info)
@@ -1788,6 +1799,7 @@ static struct kvmppc_ops kvm_ops_pr = {
 	.arch_vm_ioctl  = kvm_arch_vm_ioctl_pr,
 #ifdef CONFIG_PPC_BOOK3S_64
 	.hcall_implemented = kvmppc_hcall_impl_pr,
+	.configure_mmu = kvm_configure_mmu_pr,
 #endif
 	.giveup_ext = kvmppc_giveup_ext,
 };