Re: [PATCH 5/5] iommu: Allow default domain type to be set on the kernel command line

[Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>]

On 26/01/17 17:15, Joerg Roedel wrote:
> On Thu, Jan 19, 2017 at 06:19:15PM +0000, Will Deacon wrote:
>> Rather than modify each IOMMU driver to provide different semantics for
>> DMA domains, instead we introduce a command line parameter that can be
>> used to change the type of the default domain. Passthrough can then be
>> specified using "iommu.default_domain=identity" on the kernel command
>> line.
> 
> I like the general idea of this, but the above is a terrible name for a
> kernel commandline-parameter. The x86 iommus support iommu=pt which is
> pretty much the same as this patch does.

Indeed, I was keen on making "iommu=pt" also do this default domain
switch itself so we wouldn't need a new option - it didn't *appear* that
that would break the AMD driver (as the only other default domain user
supporting identity domains) but I may have overlooked something.

Robin.

> How about something like "iommu.passthrough=0/1"? And please add the
> parameter to the kernel documentation too.
> 
> 
> 	Joerg
>