[RFC PATCH v4 03/16] iommu/arm-smmu-v3: Add initial pSMMU realm viommu plumbing

[Aneesh Kumar K.V]

Jason Gunthorpe <jgg at ziepe.ca> writes:

> On Wed, Sep 02, 2026 at 02:30:00PM +0530, Aneesh Kumar K.V wrote:
>> Jason Gunthorpe <jgg at ziepe.ca> writes:
>> 
>> > On Tue, Sep 01, 2026 at 03:36:37PM +0530, Aneesh Kumar K.V wrote:
>> >
>> >> @@ -463,14 +460,13 @@
>> >>  	vsmmu->vmid = s2_parent->s2_cfg.vmid;
>> >>  
>> >>  	if (viommu->type == IOMMU_VIOMMU_TYPE_ARM_SMMUV3) {
>> >> +		if (arm_smmu_is_realm_viommu(viommu))
>> >> +			return arm_realm_smmu_v3_init(viommu, user_data);
>> >> +
>> >
>> > I think the realm vsmmu is going to require a different info struct
>> > than the normal psmmu case, isn't it?
>> >
>> > If so it needs its own enum value.
>> >
>> > It would be nice to see a draft patch showing how the real vsmmu works
>> > on top of the RMM spec for it. If we are using a viommu object then
>> > non-vsmmu case should be identical just with an option in the info
>> > struct to not create the vsmmu object.
>> 
>> Based on feedback on other emails in this thread, I have now implemented
>> this without using a vdevice or viommu. This should make the CCA and
>> non-CCA cases similar.
>
> That wasn't the feedback. The feedback was to use the viommu and not
> make a bunch of new stuff..
>

That rework was done before I saw your discussion with Nicolin.

To reiterate, for this configuration:

- The viommu will use a stage-1 bypass configuration.
- A new IOMMU_VIOMMU_TYPE_ARM_REALM_SMMUV3 type will create the viommu.
  The psmmu will be activated at this point to avoid creating psmmu
  objects early. We will reference-count it to ensure that the same
  psmmu is shared across realm guests.
- Creating a vdevice will invoke SMC_RMI_PSMMU_ST_L2_CREATE.

I am unclear about the vdev_create suggestion. Creating a vdevice
requires an RD, which is created later in the flow above. How do you
suggest linking vdevice_alloc to vdev_create?

>From the RMM's perspective, the sequence is as follows:

viommu alloc 

[   rmm ] SMC_RMI_PSMMU_ACTIVATE            2b400000 8819bb000 > RMI_INCOMPLETE 0 10008
[   rmm ]       SMC_RMI_OP_MEM_DONATE       0 881bac098 1 > RMI_INCOMPLETE 2 10004
[   rmm ]       SMC_RMI_OP_MEM_DONATE       0 881bac098 1 > RMI_INCOMPLETE 1 10004
[   rmm ]       SMC_RMI_OP_MEM_DONATE       0 881bac098 1 > RMI_INCOMPLETE 1 0
[   rmm ] L1 StrTab: PA 0x881baa000 VA 0x80003c0000 size 0x2000
[   rmm ] CMDQ: PA 0x88066a000 VA 0x80003c2000
[   rmm ] EVTQ: PA 0x8815c5000 VA 0x80003c3000
[   rmm ] PSMMU 0x2b400000 activated
[   rmm ]       SMC_RMI_OP_CONTINUE         0 0 > RMI_SUCCESS 0 0
[   rmm ] SMC_RMI_PSMMU_ST_L2_CREATE        2b400000 300 > RMI_INCOMPLETE 0 10004
[   rmm ]       SMC_RMI_OP_MEM_DONATE       0 881bac098 1 > RMI_INCOMPLETE 1 0
[   rmm ] smmu->strtab_base[12] 0x0 @0x80003c0060
[   rmm ] L1STD[12] 0x8819bb007 for SID 0x300: L2 table VA 0x80003d0000 PA 0x8819bb000
[   rmm ]       SMC_RMI_OP_CONTINUE         0 0 > RMI_SUCCESS 0 0

vdevice alloc

[   rmm ] SMC_RMI_PSMMU_ST_L2_CREATE        2b400000 200 > RMI_INCOMPLETE 0 10004
[   rmm ]       SMC_RMI_OP_MEM_DONATE       0 882648098 1 > RMI_INCOMPLETE 1 0
[   rmm ] smmu->strtab_base[8] 0x0 @0x80003c0040
[   rmm ] L1STD[8] 0x882506007 for SID 0x200: L2 table VA 0x80003cc000 PA 0x882506000
[   rmm ]       SMC_RMI_OP_CONTINUE         0 0 > RMI_SUCCESS 0 0

RD gets allocated here

[   rmm ] SMC_RMI_REALM_CREATE              881b03000 8819a1000 > RMI_INCOMPLETE 0 24
[   rmm ]       SMC_RMI_OP_MEM_DONATE       0 881605098 9 > RMI_INCOMPLETE 9 0
[   rmm ]       SMC_RMI_OP_CONTINUE         0 0 > RMI_SUCCESS 0 0

-aneesh