Re: [PATCH/RFC 03/09] iommu/ipmmu-vmsa: Introduce keepipmmu boot parameter

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Magnus,

On Wed, Feb 20, 2019 at 3:55 PM Magnus Damm <magnus.damm@gmail.com> wrote:
> From: Magnus Damm <damm+renesas@opensource.se>
>
> Introduce a keepipmmu boot paramenter to let the user override.
>
> Not-Yet-Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
> ---
>
>  drivers/iommu/ipmmu-vmsa.c |   14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
>
> --- 0004/drivers/iommu/ipmmu-vmsa.c
> +++ work/drivers/iommu/ipmmu-vmsa.c     2019-02-20 23:17:54.038850305 +0900
> @@ -759,6 +759,17 @@ static int ipmmu_init_platform_device(st
>         return 0;
>  }
>
> +
> +static int keep_ipmmu;
> +
> +static int __init keepipmmu_setup(char *__unused)
> +{
> +       keep_ipmmu = 1;
> +       return 1;
> +}
> +
> +__setup("keepipmmu", keepipmmu_setup);

Documentation/admin-guide/kernel-parameters.txt shows other IOMMUs
implement binary parameters, which allow to override the default, to
disable or enable the IOMMU.

Perhaps you want the default to be enabled when running in HYP mode,
so the IPMMU can be used for KVM+VFIO device pass-through?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds