Re: [Xen-devel] [PATCH v3 3/3] xen: make available hvm_fep to non-debug build as well

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 23/06/16 13:44, Wei Liu wrote:
> On Thu, Jun 23, 2016 at 06:20:38AM -0600, Jan Beulich wrote:
>>>>> On 23.06.16 at 12:50, <wei.liu2@xxxxxxxxxx> wrote:
>>> On Wed, Jun 22, 2016 at 09:42:38AM -0600, Jan Beulich wrote:
>>>>>>> On 20.06.16 at 18:30, <wei.liu2@xxxxxxxxxx> wrote:
>>>>> @@ -97,9 +98,17 @@ boolean_param("hap", opt_hap_enabled);
>>>>>  
>>>>>  #ifndef opt_hvm_fep
>>>>>  /* Permit use of the Forced Emulation Prefix in HVM guests */
>>>>> -bool_t opt_hvm_fep;
>>>>> +bool_t __read_mostly opt_hvm_fep;
>>>>>  boolean_param("hvm_fep", opt_hvm_fep);
>>>>>  #endif
>>>>> +static const char __initconst *warning_hvm_fep =
>>>>> +    "**********************************************\n"
>>>>> +    "******* WARNING: HVM FORCED EMULATION PREFIX IS AVAILABLE\n"
>>>>> +    "******* This option is *ONLY* intended to aid testing of Xen.\n"
>>>>> +    "******* It has implications on the security of the system.\n"
>>>>> +    "******* Please *DO NOT* use this in production.\n"
>>>>> +    "**********************************************\n";
>>>>> +
>>>>>  
>>>> Along with the same comment as on patch 2, here even more than
>>>> there I wonder whether this string wouldn't better be a static local
>>>> in hvm_enable() (or even the scope therein where warning_add()
>>>> gets invoked).
>>> I would rather the text stays next to where the option is defined so
>>> it is obvious to anyone who touches this area of code.
>> Makes sense. But then - shouldn't it move inside the #ifndef?
>>
> That would then require the warning_add() call to be wrapped in ifdef,
> too. That looks a bit cumbersome to me.

You can do something like:

#ifndef $FOO
#define warning_text NULL
#else
const static __initdata warning_text[] = "BAR";
#endif

This works in the same way as the current opt_hvm_fep define.

~Andrew

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