On Wed, Dec 19, 2012 at 12:01:19AM +0100, Alexander Graf wrote: > > On 18.12.2012, at 23:54, Scott Wood wrote: > > > On 12/18/2012 06:38:41 AM, Alexander Graf wrote: > >> When we hit an emulation result that we didn't expect, that is an error, > >> but it's nothing that warrants a BUG(), because it can be guest triggered. > >> So instead, let's only WARN() the user that this happened. > >> Signed-off-by: Alexander Graf <agraf@xxxxxxx> > >> --- > >> arch/powerpc/kvm/powerpc.c | 3 ++- > >> 1 files changed, 2 insertions(+), 1 deletions(-) > >> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c > >> index be83fca..e2225e5 100644 > >> --- a/arch/powerpc/kvm/powerpc.c > >> +++ b/arch/powerpc/kvm/powerpc.c > >> @@ -237,7 +237,8 @@ int kvmppc_emulate_mmio(struct kvm_run *run, struct kvm_vcpu *vcpu) > >> r = RESUME_HOST; > >> break; > >> default: > >> - BUG(); > >> + WARN_ON(1); > >> + r = RESUME_GUEST; > > > > Do you have a specific way of a guest triggering this in mind, or is it just being cautious? The guest probably shouldn't be allowed to spam the kernel log with WARNs either. Is a traceback even useful here? > > For debugging, yes. But maybe we would be better off with a trace point. Anyway, a WARN is better than a BUG either way for now. > > I was able to provoke this by live patching an instruction without flushing the icache, so that the last_inst instruction fetch gets a different instruction from the instruction that resulted in the trap we're currently in. > If guest can trigger this it better be WARN_ON_ONCE(). Otherwise, as Scott said, guest will be able to spam host kernel log. -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
