Re: [PATCH 1/2] xen/xsm: Introduce new boot parameter xsm

["Xin Li (Talons)" <xin.li@citrix.com>]

Hello Jan


> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@suse.com]
> Sent: Monday, July 2, 2018 4:25 PM
> To: Xin Li (Talons) <xin.li@citrix.com>; Xin Li <talons.lee@gmail.com>
> Cc: Andrew Cooper <Andrew.Cooper3@citrix.com>; George Dunlap
> <George.Dunlap@citrix.com>; Ming Lu <ming.lu@citrix.com>; Sergey Dyasli
> <sergey.dyasli@citrix.com>; Wei Liu <wei.liu2@citrix.com>; Stefano Stabellini
> <sstabellini@kernel.org>; xen-devel@lists.xen.org; Konrad Rzeszutek Wilk
> <konrad.wilk@oracle.com>; Daniel de Graaf <dgdegra@tycho.nsa.gov>; Tim
> (Xen.org) <tim@xen.org>
> Subject: RE: [PATCH 1/2] xen/xsm: Introduce new boot parameter xsm
> 
> >>> On 02.07.18 at 09:34, <xin.li@citrix.com> wrote:
> >> From: Jan Beulich [mailto:JBeulich@suse.com]
> >> Sent: Friday, June 29, 2018 6:05 PM
> >> >>> On 29.06.18 at 11:47, <andrew.cooper3@citrix.com> wrote:
> >> > On 29/06/18 10:28, Xin Li wrote:
> >> >> --- a/docs/misc/xen-command-line.markdown
> >> >> +++ b/docs/misc/xen-command-line.markdown
> >> >> @@ -865,6 +865,19 @@ hardware domain is architecture dependent.
> >> >>  Note that specifying zero as domU value means zero, while for
> >> >> dom0 it means  to use the default.
> >> >>
> >> >> +### xsm
> >> >> +> `= dummy | silo | flask`
> >> >
> >> > This should be just "dummy | flask" in this patch, and extended
> >> > with silo in the next path.  Also, options in this file should be
> >> > sorted alphabetically, so ### xsm should be near the end, rather than
> beside flask.
> >> >
> >> >> +
> >> >> +> Default: `dummy`
> >> >> +
> >> >> +Specify which XSM module should be enabled.  This option is only
> >> >> +available if the hypervisor was compiled with XSM support.
> >> >> +
> >> >> +* `dummy`: this is the default choice.  No special restriction will be
> applied.
> >> >> +  it's also used when XSM is compiled out.
> >> >> +enum xsm_bootparam __read_mostly xsm_bootparam =
> >> >> +XSM_BOOTPARAM_DUMMY;
> >>
> >> So why "dummy" instead of "none" (or one of the boolean false strings)?
> >
> > It seems dummy is not fully stub. (some check by XSM_* classification)
> > So we want to keep this "dummy" check, and override it.
> 
> Right, except that "dummy", while a reasonable name internally to the
> implementation, is at least of questionable use/meaning as a part of a
> command line option.
is it better to keep them the same?

> 
> >> >> @@ -57,7 +81,20 @@ static int __init xsm_core_init(const void
> >> *policy_buffer, size_t policy_size)
> >> >>      }
> >> >>
> >> >>      xsm_ops = &dummy_xsm_ops;
> >> >> -    flask_init(policy_buffer, policy_size);
> >> >> +
> >> >> +    switch ( xsm_bootparam )
> >> >> +    {
> >> >> +    case XSM_BOOTPARAM_DUMMY:
> >> >> +        /* empty */
> >>
> >> I'm not sure of the value of this comment.
> > I just want avoid an empty switch case.
> 
> Well, it's not empty because of ...
> 
> >> >> +        break;
> 
> ... this (without which it would be a fall-through one).

Oh, OK, remove this comment.

> 
> Jan
> 


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