KVM: PPC: Emulate segment fault

Book3S_32 doesn't know about segment faults. It only knows about page faults.
So in order to know that we didn't map a segment, we need to fake segment
faults.

We do this by setting invalid segment registers to an invalid VSID and then
check for that VSID on normal page faults.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
index d0986968a611..f8ac26599f6d 100644
--- a/arch/powerpc/kvm/book3s.c
+++ b/arch/powerpc/kvm/book3s.c
@@ -775,6 +775,18 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
         switch (exit_nr) {
         case BOOK3S_INTERRUPT_INST_STORAGE:
                 vcpu->stat.pf_instruc++;
+
+#ifdef CONFIG_PPC_BOOK3S_32
+                /* We set segments as unused segments when invalidating them. So
+                 * treat the respective fault as segment fault. */
+                if (to_svcpu(vcpu)->sr[kvmppc_get_pc(vcpu) >> SID_SHIFT]
+                    == SR_INVALID) {
+                        kvmppc_mmu_map_segment(vcpu, kvmppc_get_pc(vcpu));
+                        r = RESUME_GUEST;
+                        break;
+                }
+#endif
+
                 /* only care about PTEG not found errors, but leave NX alone */
                 if (to_svcpu(vcpu)->shadow_srr1 & 0x40000000) {
                         r = kvmppc_handle_pagefault(run, vcpu, kvmppc_get_pc(vcpu), exit_nr);
@@ -799,6 +811,17 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
         {
                 ulong dar = kvmppc_get_fault_dar(vcpu);
                 vcpu->stat.pf_storage++;
+
+#ifdef CONFIG_PPC_BOOK3S_32
+                /* We set segments as unused segments when invalidating them. So
+                 * treat the respective fault as segment fault. */
+                if ((to_svcpu(vcpu)->sr[dar >> SID_SHIFT]) == SR_INVALID) {
+                        kvmppc_mmu_map_segment(vcpu, dar);
+                        r = RESUME_GUEST;
+                        break;
+                }
+#endif
+
                 /* The only case we need to handle is missing shadow PTEs */
                 if (to_svcpu(vcpu)->fault_dsisr & DSISR_NOHPTE) {
                         r = kvmppc_handle_pagefault(run, vcpu, dar, exit_nr);