KVM: PPC: Book3S: Allow XICS emulation to work in nested hosts using XIVE

Currently, the KVM code assumes that if the host kernel is using the
XIVE interrupt controller (the new interrupt controller that first
appeared in POWER9 systems), then the in-kernel XICS emulation will
use the XIVE hardware to deliver interrupts to the guest.  However,
this only works when the host is running in hypervisor mode and has
full access to all of the XIVE functionality.  It doesn't work in any
nested virtualization scenario, either with PR KVM or nested-HV KVM,
because the XICS-on-XIVE code calls directly into the native-XIVE
routines, which are not initialized and cannot function correctly
because they use OPAL calls, and OPAL is not available in a guest.

This means that using the in-kernel XICS emulation in a nested
hypervisor that is using XIVE as its interrupt controller will cause a
(nested) host kernel crash.  To fix this, we change most of the places
where the current code calls xive_enabled() to select between the
XICS-on-XIVE emulation and the plain XICS emulation to call a new
function, xics_on_xive(), which returns false in a guest.

However, there is a further twist.  The plain XICS emulation has some
functions which are used in real mode and access the underlying XICS
controller (the interrupt controller of the host) directly.  In the
case of a nested hypervisor, this means doing XICS hypercalls
directly.  When the nested host is using XIVE as its interrupt
controller, these hypercalls will fail.  Therefore this also adds
checks in the places where the XICS emulation wants to access the
underlying interrupt controller directly, and if that is XIVE, makes
the code use the virtual mode fallback paths, which call generic
kernel infrastructure rather than doing direct XICS access.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

1 files changed, 8 insertions, 8 deletions

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 27112b70aa7a..1860c0bc1395 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -922,7 +922,7 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu)
 	case H_IPOLL:
 	case H_XIRR_X:
 		if (kvmppc_xics_enabled(vcpu)) {
-			if (xive_enabled()) {
+			if (xics_on_xive()) {
 				ret = H_NOT_AVAILABLE;
 				return RESUME_GUEST;
 			}
@@ -1431,7 +1431,7 @@ static int kvmppc_handle_nested_exit(struct kvm_run *run, struct kvm_vcpu *vcpu)
 	case BOOK3S_INTERRUPT_HV_RM_HARD:
 		vcpu->arch.trap = 0;
 		r = RESUME_GUEST;
-		if (!xive_enabled())
+		if (!xics_on_xive())
 			kvmppc_xics_rm_complete(vcpu, 0);
 		break;
 	default:
@@ -3649,7 +3649,7 @@ static void shrink_halt_poll_ns(struct kvmppc_vcore *vc)
 #ifdef CONFIG_KVM_XICS
 static inline bool xive_interrupt_pending(struct kvm_vcpu *vcpu)
 {
-	if (!xive_enabled())
+	if (!xics_on_xive())
 		return false;
 	return vcpu->arch.irq_pending || vcpu->arch.xive_saved_state.pipr <
 		vcpu->arch.xive_saved_state.cppr;
@@ -4209,7 +4209,7 @@ static int kvmppc_vcpu_run_hv(struct kvm_run *run, struct kvm_vcpu *vcpu)
 				vcpu->arch.fault_dar, vcpu->arch.fault_dsisr);
 			srcu_read_unlock(&kvm->srcu, srcu_idx);
 		} else if (r == RESUME_PASSTHROUGH) {
-			if (WARN_ON(xive_enabled()))
+			if (WARN_ON(xics_on_xive()))
 				r = H_SUCCESS;
 			else
 				r = kvmppc_xics_rm_complete(vcpu, 0);
@@ -4733,7 +4733,7 @@ static int kvmppc_core_init_vm_hv(struct kvm *kvm)
 		 * If xive is enabled, we route 0x500 interrupts directly
 		 * to the guest.
 		 */
-		if (xive_enabled())
+		if (xics_on_xive())
 			lpcr |= LPCR_LPES;
 	}
 
@@ -4969,7 +4969,7 @@ static int kvmppc_set_passthru_irq(struct kvm *kvm, int host_irq, int guest_gsi)
 	if (i == pimap->n_mapped)
 		pimap->n_mapped++;
 
-	if (xive_enabled())
+	if (xics_on_xive())
 		rc = kvmppc_xive_set_mapped(kvm, guest_gsi, desc);
 	else
 		kvmppc_xics_set_mapped(kvm, guest_gsi, desc->irq_data.hwirq);
@@ -5010,7 +5010,7 @@ static int kvmppc_clr_passthru_irq(struct kvm *kvm, int host_irq, int guest_gsi)
 		return -ENODEV;
 	}
 
-	if (xive_enabled())
+	if (xics_on_xive())
 		rc = kvmppc_xive_clr_mapped(kvm, guest_gsi, pimap->mapped[i].desc);
 	else
 		kvmppc_xics_clr_mapped(kvm, guest_gsi, pimap->mapped[i].r_hwirq);
@@ -5387,7 +5387,7 @@ static int kvmppc_book3s_init_hv(void)
 	 * indirectly, via OPAL.
 	 */
 #ifdef CONFIG_SMP
-	if (!xive_enabled() && !kvmhv_on_pseries() &&
+	if (!xics_on_xive() && !kvmhv_on_pseries() &&
 	    !local_paca->kvm_hstate.xics_phys) {
 		struct device_node *np;