Re: [Xen-devel] [PATCH v2] x86/emul: Split exception handling out of invoke_stub()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 31.01.18 at 13:50, <andrew.cooper3@xxxxxxxxxx> wrote:
> For a release build, bloat-o-meter reports:
> 
>   add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-5111 (-5111)
>   function                                     old     new   delta
>   x86_emulate                               126458  121347   -5111
> 
> or in other words, a 4% redunction in code size from this change alone.
> 
> The use of __LINE__ is a concern with livepatching, but any livepatch touching
> this file is overwhemlingly likely to alter x86_emulate() anyway.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> CC: Jan Beulich <JBeulich@xxxxxxxx>
> 
> v2:
>  * Retain __LINE__.  It can't be embedded in union stub_exception_token as the
>    full token gets written by the exception hanlder.

And that's not what I had in mind. Instead I had thought of ...

> @@ -3017,6 +3008,10 @@ x86_emulate(
>      struct fpu_insn_ctxt fic = { .type = X86EMUL_FPU_none, .exn_raised = -1 
> };
>      struct x86_emulate_stub stub = {};
>      DECLARE_ALIGNED(mmval_t, mmval);
> +#ifdef __XEN__
> +    union stub_exception_token stub_exn_info;
> +    unsigned int stub_exn_line;
> +#endif

    struct {
        union stub_exception_token info;
        unsigned int line;
    } stub_exn;

Either way
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Jan


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