Re: [Xen-devel] [PATCH SpectreV1+L1TF v4 01/11] is_control_domain: block speculation

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 23.01.19 at 12:51, <nmanthey@xxxxxxxxx> wrote:
> --- a/xen/include/xen/nospec.h
> +++ b/xen/include/xen/nospec.h
> @@ -58,6 +58,21 @@ static inline unsigned long 
> array_index_mask_nospec(unsigned long index,
>      (typeof(_i)) (_i & _mask);                                          \
>  })
>  
> +/*
> + * allow to insert a read memory barrier into conditionals
> + */

Please obey to the comment style set forth in ./CODING_STYLE.

> +#ifdef CONFIG_X86
> +static inline bool lfence_true(void) { rmb(); return true; }
> +#else
> +static inline bool lfence_true(void) { return true; }
> +#endif

This is a generic header, hence functions defined here should have
universally applicable names. "lfence", however, is an x86 term
(naming a particular instruction). I can't think of really good
alternatives, but how about one of arch_nospec_true() /
arch_fence_nospec_true() / arch_nospec_fence_true()?

Furthermore, rather than adding Kconfig control and alternatives
patching later in the series (as per the cover letter), it should be
that way from the beginning. Remember that any series may go
in piecemeal, not all in one go.

Jan



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