On 1/23/19 15:45, Jan Beulich wrote:
>>>> On 23.01.19 at 14:44, <julien.gr...@arm.com> wrote:
>> On 23/01/2019 13:39, Jan Beulich wrote:
>>>>>> On 23.01.19 at 14:24, <julien.gr...@arm.com> wrote:
>>>> On 23/01/2019 11:51, Norbert Manthey wrote:
>>>>> --- a/xen/include/xen/nospec.h
>>>>> +++ b/xen/include/xen/nospec.h
>>>>> @@ -68,10 +68,18 @@ static inline bool lfence_true(void) { return true; }
>>>>> #endif
>>>>>
>>>>> /*
>>>>> - * protect evaluation of conditional with respect to speculation
>>>>> + * allow to protect evaluation of conditional with respect to
>>>>> speculation on x86
>>>>> */
>>>>> -#define evaluate_nospec(condition) \
>>>>> +#if defined(CONFIG_L1TF_LFENCE_NONE) || !defined(CONFIG_X86)
>>>>> +#define evaluate_nospec(condition) (condition)
>>>>> +#elif defined(CONFIG_L1TF_LFENCE_BOTH)
>>>>> +#define evaluate_nospec(condition)
>>>>> \
>>>>> (((condition) && lfence_true()) || !lfence_true())
>>>>> +#elif defined(CONFIG_L1TF_LFENCE_TRUE)
>>>>> +#define evaluate_nospec(condition) ((condition) && lfence_true())
>>>>> +#elif defined(CONFIG_L1TF_LFENCE_INTERMEDIATE)
>>>>> +#define evaluate_nospec(condition) ({ bool res = (condition); rmb();
>>>>> res; })
>>>> +#endif
>>>>
>>>> None of the configs are defined on Arm, so can this be moved in arch-x86?
>>> To be honest I'd like to avoid introducing asm/nospec.h for the time
>>> being.
>> How about adding them in system.h as we did for array_index_mask_nospec?
> To tell you the truth, that's where Norbert had it originally.
> I think that's not the right place though (also for
> array_index_mask_nospec()). But I'll listen to a majority
> thinking differently, at least as far as what is currently
> lfence_true() goes. evaluate_nospec(), otoh, belongs where
> it is now, I think.
I will rename the lfence_true macro into "arch_barrier_nospec_true".
Furthermore, I will merge the introduction of the macros with the
introduction of the configuration and the alternative patching. Finally,
I'll reuse the arch_barrier_nospec_true implementation in the
evaluate_nospec macro.
Best,
Norbert
>
> Jan
>
>
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