Re: [dpdk-dev] [PATCH v3 0/3] force IOVA to a particular mode

["Burakov, Anatoly" <anatoly.burakov@intel.com>]

On 30-Oct-18 12:02 PM, Alejandro Lucero wrote:
> 
> 
> On Sun, Oct 28, 2018 at 11:04 PM Thomas Monjalon <thomas@monjalon.net 
> <mailto:thomas@monjalon.net>> wrote:
> 
>     11/10/2018 12:08, Thomas Monjalon:
>      > +Cc more maintainers in order to collect more reviews
>      >
>      > 04/10/2018 11:19, Burakov, Anatoly:
>      > > On 03-Oct-18 9:53 PM, eric zhang wrote:
>      > > > This patchset introduces an EAL command line option "--iova-mode"
>      > > > to give the user a facility to force IOVA mode to a special
>     value.
>      > > >
>      > > > Auto detection of the IOVA mode, based on probing the bus and
>     IOMMU
>      > > > configuration, may not report the desired addressing mode
>     when virtual
>      > > > devices that are not directly attached to the bus are present.
>      > > > The EAL command line option "--iova-mode" can be used to
>     select either
>      > > > physical addressing('pa') or virtual addressing('va').
>      > >
>      > > Acked-by: Anatoly Burakov <anatoly.burakov@intel.com
>     <mailto:anatoly.burakov@intel.com>>
> 
>     Rebased and applied, thanks
> 
> 
> 
> Could not this lead to a problem if a device can not wok with the mode set?
> For example, IOVA mode set to VA and IOMMU hw with less bits than those 
> required for the virtual addresses?
> 
> IMO any device should be attached to a bus, and a bus should have a 
> function for setting IOVA mode and the --iova-mode option just allowed 
> with supported IOVA modes within the bus.

I don't think it should work that way. It should warn the user that an 
incompatible IOVA mode was selected, but the user has specified an IOVA 
mode for a reason - it probably implies he really means it, so let him :)

-- 
Thanks,
Anatoly