Re: [Xen-devel] [PATCH v8 1/2] x86emul: New return code for unimplemented instruction

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 08.08.17 at 20:06, <ppircalabu@xxxxxxxxxxxxxxx> wrote:
> --- a/xen/arch/x86/hvm/emulate.c
> +++ b/xen/arch/x86/hvm/emulate.c

What about the use in a switch() statement in hvmemul_do_io()
in this file? And the use in hvmemul_do_io_buffer()?

> @@ -2044,6 +2044,8 @@ int hvm_emulate_one_mmio(unsigned long mfn, unsigned 
> long gla)
>      switch ( rc )
>      {
>      case X86EMUL_UNHANDLEABLE:
> +        /* fall-through */
> +    case X86EMUL_UNIMPLEMENTED:

The fall-through comment is pointless in such a case.

hvm/intercept.c has a use in hvm_process_io_intercept() which
looks like it needs dealing with too. And there are more. Any
places you perhaps leave alone intentionally should be reasoned
about in the description.

> @@ -7717,7 +7717,7 @@ x86_emulate(
>  
>      default:
>      cannot_emulate:
> -        rc = X86EMUL_UNHANDLEABLE;
> +        rc = X86EMUL_UNIMPLEMENTED;

There's at least one goto to the label here which can't stay as is
(in invoke_stub()). Did you really audit them all?

Jan


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