On 12/18/2012 05:01:19 PM, 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.
I figured the interesting bits would be in the stack frames you've just
returned from.
But maybe we would be better off with a trace point.
Or a ratelimited error message, and maybe we should return to host
instead of guest?
Anyway, a WARN is better than a BUG either way for now.
Yes...
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.
Which EMULATE code did you get in that case?
-Scott
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