Re: [Xen-devel] [PATCH SpectreV1+L1TF v5 4/9] spec: add l1tf-barrier

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 06.02.19 at 14:02, <nmanthey@xxxxxxxxx> wrote:
> On 2/5/19 15:43, Jan Beulich wrote:
>>>>> On 05.02.19 at 15:23, <nmanthey@xxxxxxxxx> wrote:
>>> On 1/31/19 17:35, Jan Beulich wrote:
>>>>>>> On 29.01.19 at 15:43, <nmanthey@xxxxxxxxx> wrote:
>>>>> +    /*
>>>>>       * We do not disable HT by default on affected hardware.
>>>>>       *
>>>>>       * Firstly, if the user intends to use exclusively PV, or HVM shadow
>>>> Furthermore, as per the comment and logic here and below a
>>>> !HVM configuration ought to be safe too, unless "pv-l1tf=" was
>>>> used (in which case we defer to the admin anyway), so it's
>>>> questionable whether the whole logic should be there in the
>>>> first place in this case. This would then in particular keep all
>>>> of this out for the PV shim.
>>> For the PV shim, I could add pv-shim to my check before enabling the CPU
>>> flag.
>> But the PV shim is just a special case. I'd like this code to be
>> compiled out for all !HVM configurations.
> 
> The that introduces the evaluate_nospec macro does that already. Based
> on defined(CONFIG_HVM) lfence patching is disabled there.

Oh, right.

> Do you want me to wrap this command line option into CONFIG_HVM checks
> as well?

That would be nice; I have a patch for post-4.12 where I do
something similar to opt_xpti_*. Therefore if you didn't do it
here, I'd probably submit a fixup patch down the road.

Jan



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