[PATCH 3/4] ACPI: IORT: Skip SMMUv3 device ID map for two steps mappings

[Lorenzo Pieralisi]

On Tue, Oct 10, 2017 at 02:47:53PM +0800, Hanjun Guo wrote:
> Hi Lorenzo,
> 
> Sorry for the late reply, holidays in China for the past week.
> 
> At 2017/9/27 21:54, Lorenzo Pieralisi wrote:
> > Hi Hanjun,
> >
> > On Wed, Sep 27, 2017 at 09:20:14AM +0800, Hanjun Guo wrote:
> >> IORT revision C introduced SMMUv3 MSI support which adding a
> >> device ID mapping index in SMMUv3 sub table, to get the SMMUv3
> >> device ID mapping for the output ID (dev ID for ITS) and the
> >> link to which ITS.
> >>
> >> So if a platform supports SMMUv3 MSI for control interrupt,
> >> there will be a additional single map entry under SMMU, this
> >> will not introduce any difference for devices just use one
> >> step map to get its output ID and parent (ITS or SMMU), such
> >> as PCI/NC/PMCG ---> ITS or PCI/NC ---> SMMU, but we need to
> >> do the special handling for two steps map case such as
> >> PCI/NC--->SMMUv3--->ITS.
> >>
> >> Take a PCI hostbridge for example,
> >>
> >> |----------------------|
> >> |  Root Complex Node   |
> >> |----------------------|
> >> |    map entry[x]      |
> >> |----------------------|
> >> |       id value       |
> >> | output_reference     |
> >> |---|------------------|
> >>      |
> >>      |   |----------------------|
> >>      |-->|        SMMUv3        |
> >>          |----------------------|
> >>          |     SMMU dev ID      |
> >>          |     mapping index 0  |
> >>          |----------------------|
> >>          |      map entry[0]    |
> >>          |----------------------|
> >>          |       id value       |
> >>          | output_reference-----------> ITS 1 (SMMU MSI domain)
> >>          |----------------------|
> >>          |      map entry[1]    |
> >>          |----------------------|
> >>          |       id value       |
> >>          | output_reference-----------> ITS 2 (PCI MSI domain)
> >>          |----------------------|
> >>
> >> When the SMMU dev ID mapping index is 0, there is entry[0]
> >> to map to a ITS, we need to skip that map entry for PCI
> >> or NC (named component), or we may get the wrong ITS parent.
> >
> > Is this actually true ? I think that currently we would simply skip
> > the entry and print an error log but we can't get a wrong ITS parent.
> 
> So the only valid single mapping under type SMMUv3 is SMMUv3's dev id
> mapping, we need to fix the IORT spec as well.
> 
> >
> > I am rewriting this commit (I will probably split it), it is doing the
> > right thing but the commit log is stale (probably caused by code
> > reshuffling).
> 
> Do I need to resend another version, or you can help to update it?
> please let me know.

I reworked the patches, you can repost/retest them I made them available
in the branch below, we will have to add a guard around ACPICA smmu
struct (unfortunately I think we will have to use the ACPICA version as
a guard) or I can ask Rafael to pull the series if ACPICA goes via ACPI
tree (and your patch made it into the release - I will check ACPICA
upstream).

git://git.kernel.org/pub/scm/linux/kernel/git/lpieralisi/linux.git iort/smmu-msi-for-4.15