Re: [PATCH v5 13/14] iommu/arm-smmu-v3: Introduce struct arm_smmu_vmaster

On Mon, Jan 13, 2025 at 03:29:27PM -0400, Jason Gunthorpe wrote:

On Tue, Jan 07, 2025 at 09:10:16AM -0800, Nicolin Chen wrote:

...

+int arm_smmu_attach_prepare_vmaster(struct arm_smmu_attach_state *state,

• 		    struct iommu_domain *domain)
  

+{

• struct arm_smmu_nested_domain *nested_domain;
• struct arm_smmu_vmaster *vmaster;
• unsigned long vsid;
• unsigned int cfg;
• iommu_group_mutex_assert(state->master->dev);
• if (domain->type != IOMMU_DOMAIN_NESTED)

• return 0;
  

• nested_domain = to_smmu_nested_domain(domain);
• /* Skip ABORT/BYPASS or invalid vSTE */
• cfg = FIELD_GET(STRTAB_STE_0_CFG, le64_to_cpu(nested_domain->ste[0]));
• if (cfg == STRTAB_STE_0_CFG_ABORT || cfg == STRTAB_STE_0_CFG_BYPASS)

• return 0;
  

Why? If the VM sets an ABORT vSTE then I would expect that any protection violation events the VM triggers are captured and forwarded as well?

Basically any time a vSTE is in place we should capture events that are affiliated with the SID?

I see. I will drop this.

...

• if (!(nested_domain->ste[0] & cpu_to_le64(STRTAB_STE_0_V)))

• return 0;
  

• vsid = iommufd_viommu_get_vdev_id(&nested_domain->vsmmu->core,

• 			  state->master->dev);
  

• /* Fail the attach if vSID is not correct set by the user space */
• if (!vsid)

• return -ENOENT;
  

Is it really OK that 0 is being used as invalid here?

Hmm, perhaps better to do an int function for -ENOENT. Will fix this.

Thanks Nicolin