Re: [Xen-devel] [PATCH v3 4/7] x86/nospec: Rename and rework l1tf-barrier as branch-harden

[Jan Beulich <jbeulich@xxxxxxxx>]

On 23.10.2019 15:58, Andrew Cooper wrote:
> l1tf-barrier is an inappropriate name, and came about because of restrictions
> on could be discussed publicly when the patches were proposed.
> 
> In practice, it is for general Spectre v1 mitigations, and is necessary in all
> cases.  An adversary which can control speculation in Xen can leak data in
> cross-core (BCBS, etc) or remote (NetSpectre) scenarios - the problem is not
> limited to just L1TF with HT active.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

> In principle it should be tristate and being disabled by default on parts
> which don't speculate, but it is too late in 4.13 to organise this.

And the fundamental issue is correctly compiling the conditions under which
to default to true and false respectively? I ask because if it was not this
then I wouldn't see what hindering factor there is to make this tristate
right away.

Jan

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