Re: [RFC v3 13/25] intel_iommu: modify x-scalable-mode to be string option

[Peter Xu]

On Wed, Feb 12, 2020 at 07:28:24AM +0000, Liu, Yi L wrote:
> > From: Peter Xu <address@hidden>
> > Sent: Wednesday, February 12, 2020 3:44 AM
> > To: Liu, Yi L <address@hidden>
> > Subject: Re: [RFC v3 13/25] intel_iommu: modify x-scalable-mode to be string
> > option
> > 
> > On Wed, Jan 29, 2020 at 04:16:44AM -0800, Liu, Yi L wrote:
> > > From: Liu Yi L <address@hidden>
> > >
> > > Intel VT-d 3.0 introduces scalable mode, and it has a bunch of
> > > capabilities related to scalable mode translation, thus there are multiple
> > combinations.
> > > While this vIOMMU implementation wants simplify it for user by
> > > providing typical combinations. User could config it by
> > > "x-scalable-mode" option. The usage is as below:
> > >
> > > "-device intel-iommu,x-scalable-mode=["legacy"|"modern"]"
> > 
> > Maybe also "off" when someone wants to explicitly disable it?
> 
> emmm, I  think x-scalable-mode should be disabled by default. It is enabled
> only when "legacy" or "modern" is configured. I'm fine to add "off" as an
> explicit way to turn it off if you think it is necessary. :-)

It's not necessary.  It'll be necessary when we remove "x-" and change
the default value.  However it'll always be good to provide all
options explicitly in the parameter starting from when we design it,
imho.  It's still experimental, so... Your call. :)

-- 
Peter Xu