ppc: Fix bug in handling of PAPR hypercall exits
Currently for powerpc, kvm_arch_handle_exit() always returns 1, meaning
that its caller - kvm_cpu_exec() - will always exit immediately afterwards
to the loop in qemu_kvm_cpu_thread_fn().
There's no need to do this. Once we've handled the hypercall there's no
reason we can't go straight around and KVM_RUN again, which is what ret = 0
will signal. The only exception might be for hypercalls which affect the
state of cpu_can_run(), however the only one that might do this is H_CEDE
and for kvm that is always handled in the kernel, not qemu.
Furtherm setting ret = 0 means that when exit_requested is set from a
hypercall, we will enter KVM_RUN once more with a signal which lets the
the kernel do its internal logic to complete the hypercall with out
actually executing any more guest code. This is important if our hypercall
also triggered a reset, which previously would re-initialize everything
without completing the hypercall. This caused the kernel to get confused
because it thought the guest was still in the middle of a hypercall when
it has actually been reset.
This patch therefore changes to ret = 0, which is both a bugfix and a small
optimization.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alexander Graf <agraf@suse.de>
diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
index 829e180..a31d278 100644
--- a/target-ppc/kvm.c
+++ b/target-ppc/kvm.c
@@ -766,7 +766,7 @@
dprintf("handle PAPR hypercall\n");
run->papr_hcall.ret = spapr_hypercall(env, run->papr_hcall.nr,
run->papr_hcall.args);
- ret = 1;
+ ret = 0;
break;
#endif
default:
