KVM: PPC: Book3S HV: Add radix checks in real-mode hypercall handlers

POWER9 running a radix guest will take some hypervisor interrupts
without going to real mode (turning off the MMU).  This means that
early hypercall handlers may now be called in virtual mode.  Most of
the handlers work just fine in both modes, but there are some that
can crash the host if called in virtual mode, notably the TCE (IOMMU)
hypercalls H_PUT_TCE, H_STUFF_TCE and H_PUT_TCE_INDIRECT.  These
already have both a real-mode and a virtual-mode version, so we
arrange for the real-mode version to return H_TOO_HARD for radix
guests, which will result in the virtual-mode version being called.

The other hypercall which is sensitive to the MMU mode is H_RANDOM.
It doesn't have a virtual-mode version, so this adds code to enable
it to be called in either mode.

An alternative solution was considered which would refuse to call any
of the early hypercall handlers when doing a virtual-mode exit from a
radix guest.  However, the XICS-on-XIVE code depends on the XICS
hypercalls being handled early even for virtual-mode exits, because
the handlers need to be called before the XIVE vCPU state has been
pulled off the hardware.  Therefore that solution would have become
quite invasive and complicated, and was rejected in favour of the
simpler, though less elegant, solution presented here.

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Tested-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

arch/powerpc/kvm/book3s_64_vio_hv.c

@@ -301,6 +301,10 @@ long kvmppc_rm_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
 	/* udbg_printf("H_PUT_TCE(): liobn=0x%lx ioba=0x%lx, tce=0x%lx\n", */
 	/* 	    liobn, ioba, tce); */
 
+	/* For radix, we might be in virtual mode, so punt */
+	if (kvm_is_radix(vcpu->kvm))
+		return H_TOO_HARD;
+
 	stt = kvmppc_find_table(vcpu->kvm, liobn);
 	if (!stt)
 		return H_TOO_HARD;
@@ -381,6 +385,10 @@ long kvmppc_rm_h_put_tce_indirect(struct kvm_vcpu *vcpu,
 	bool prereg = false;
 	struct kvmppc_spapr_tce_iommu_table *stit;
 
+	/* For radix, we might be in virtual mode, so punt */
+	if (kvm_is_radix(vcpu->kvm))
+		return H_TOO_HARD;
+
 	stt = kvmppc_find_table(vcpu->kvm, liobn);
 	if (!stt)
 		return H_TOO_HARD;
@@ -491,6 +499,10 @@ long kvmppc_rm_h_stuff_tce(struct kvm_vcpu *vcpu,
 	long i, ret;
 	struct kvmppc_spapr_tce_iommu_table *stit;
 
+	/* For radix, we might be in virtual mode, so punt */
+	if (kvm_is_radix(vcpu->kvm))
+		return H_TOO_HARD;
+
 	stt = kvmppc_find_table(vcpu->kvm, liobn);
 	if (!stt)
 		return H_TOO_HARD;
@@ -527,6 +539,7 @@ long kvmppc_rm_h_stuff_tce(struct kvm_vcpu *vcpu,
 	return H_SUCCESS;
 }
 
+/* This can be called in either virtual mode or real mode */
 long kvmppc_h_get_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
 		      unsigned long ioba)
 {

arch/powerpc/kvm/book3s_hv_builtin.c

@@ -207,7 +207,14 @@ EXPORT_SYMBOL_GPL(kvmppc_hwrng_present);
 
 long kvmppc_h_random(struct kvm_vcpu *vcpu)
 {
-	if (powernv_get_random_real_mode(&vcpu->arch.gpr[4]))
+	int r;
+
+	/* Only need to do the expensive mfmsr() on radix */
+	if (kvm_is_radix(vcpu->kvm) && (mfmsr() & MSR_IR))
+		r = powernv_get_random_long(&vcpu->arch.gpr[4]);
+	else
+		r = powernv_get_random_real_mode(&vcpu->arch.gpr[4]);
+	if (r)
 		return H_SUCCESS;
 
 	return H_HARDWARE;