KVM: PPC: Be more informative on BUG

We have a condition in the ppc64 host mmu code that should never occur.
Unfortunately, it just did happen to me and I was rather puzzled on why,
because BUG_ON doesn't tell me anything useful.

So let's add some more debug output in case this goes wrong. Also change
BUG to WARN, since I don't want to reboot every time I mess something up.

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

1 files changed, 8 insertions, 2 deletions

diff --git a/arch/powerpc/kvm/book3s_64_mmu_host.c b/arch/powerpc/kvm/book3s_64_mmu_host.c
index 41af12fb1260..5545c45ea57f 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_host.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_host.c
@@ -231,10 +231,16 @@ int kvmppc_mmu_map_page(struct kvm_vcpu *vcpu, struct kvmppc_pte *orig_pte)
         vcpu->arch.mmu.esid_to_vsid(vcpu, orig_pte->eaddr >> SID_SHIFT, &vsid);
         map = find_sid_vsid(vcpu, vsid);
         if (!map) {
-                kvmppc_mmu_map_segment(vcpu, orig_pte->eaddr);
+                ret = kvmppc_mmu_map_segment(vcpu, orig_pte->eaddr);
+                WARN_ON(ret < 0);
                 map = find_sid_vsid(vcpu, vsid);
         }
-        BUG_ON(!map);
+        if (!map) {
+                printk(KERN_ERR "KVM: Segment map for 0x%llx (0x%lx) failed\n",
+                                vsid, orig_pte->eaddr);
+                WARN_ON(true);
+                return -EINVAL;
+        }
 
         vsid = map->host_vsid;
         va = hpt_va(orig_pte->eaddr, vsid, MMU_SEGSIZE_256M);