Re: [PATCH v13 6/6] iommu: Remove mode argument from iommu_set_dma_strict()

[Lu Baolu]

On 6/17/21 3:41 PM, John Garry wrote:
> > > @@ -349,10 +349,9 @@ static int __init iommu_dma_setup(char *str)
> > >   }
> > >   early_param("iommu.strict", iommu_dma_setup);
> > > -void iommu_set_dma_strict(bool strict)
> > > +void iommu_set_dma_strict(void)
> > >   {
> > > -    if (strict || !(iommu_cmd_line & IOMMU_CMD_LINE_STRICT))
> > > -        iommu_dma_strict = strict;
> > > +    iommu_dma_strict = true;
> >
> > Sorry, I still can't get how iommu.strict kernel option works.
> >
> > static int __init iommu_dma_setup(char *str)
> > {
> >          int ret = kstrtobool(str, &iommu_dma_strict);
> >
> >          if (!ret)
> >                  iommu_cmd_line |= IOMMU_CMD_LINE_STRICT;
> >          return ret;
> > }
> > early_param("iommu.strict", iommu_dma_setup);
> >
> > The bit IOMMU_CMD_LINE_STRICT is only set, but not used anywhere.
>
> It is used in patch 2/6:
>
> +    pr_info("DMA domain TLB invalidation policy: %s mode %s\n",
> +        iommu_dma_strict ? "strict" : "lazy",
> +        (iommu_cmd_line & IOMMU_CMD_LINE_STRICT) ?
> +            "(set via kernel command line)" : "");
>
> > Hence,
> > I am wondering how could it work? A bug or I missed anything?
>
> It is really just used for informative purpose now.

I am clear now. Thanks!

Best regards,
baolu