Re: [PATCH] x86: fix "xpti=" and "pv-l1tf=" yet again

[Juergen Gross <jgross@suse.com>]

On 21/08/18 12:44, Jan Beulich wrote:
> While commit 2a3b34ec47 ("x86/spec-ctrl: Yet more fixes for xpti=
> parsing") indeed fixed "xpti=dom0", it broke "xpti=no-dom0", in that
> this then became equivalent to "xpti=no". In particular, the presence
> of "xpti=" alone on the command line means nothing as to which
> default is to be overridden; "xpti=no-dom0" ought to have no effect
> for DomU-s (and vice versa), as this is distinct from both
> "xpti=no-dom0,domu" and "xpti=no-dom0,no-domu".
> 
> Here as well as for "pv-l1tf=" I think there's no way around tracking
> the "use default" state separately for Dom0 and DomU-s. Introduce
> individual bits for this, and convert the variables' types (back) to
> uint8_t.
> 
> Additionally the earlier change claimed to have got rid of the
> 'parameter "xpti" has invalid value "", rc=-22!' log message for "xpti"
> alone on the command line, which wasn't the case (the option took effect
> nevertheless). Fix this as well.
> 
> Finally also support a "default" sub-option for "pv-l1tf=", just like
> "xpti=" does.
> 
> It is perhaps worth to note that OPT_<what>_DOM<which>_DEFAULT set
> implies OPT_<what>_DOM<which> clear, which is being utilized in a number
> of places (we effectively want to hold two tristates in a single
> variable, which means the fourth state is impossible).

Another possibility would be to have two local variables holding the
bits to clear and to set and to apply those after each sub-option
parsed.


Juergen

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