[PATCH v6 09/10] iommu/riscv: Add dirty tracking support for second-stage domains

[Jason Gunthorpe]

On Mon, Nov 02, 2026 at 05:18:23PM +0800, Gong Shuai wrote:
> >@@ -1439,6 +1454,9 @@ static int riscv_iommu_init_domain_s2(struct device *dev,
> > 	if (domain->gscid < 0)
> > 		return -ENOMEM;
> > 
> >+	if (iommu->caps & RISCV_IOMMU_CAPABILITIES_AMO_HWAD)
> >+		domain->domain.dirty_ops = &riscv_iommu_dirty_ops;
> 
> This sets dirty_ops based on whether the allocating device's IOMMU
> supports AMO_HWAD. As I understand it, the domain/HWPT is not tied
> to that IOMMU instance. A later attach may target a device behind
> another instance without AMO_HWAD, and the attach can still succeed
> with GADE disabled, potentially causing guest page faults.
> 
> Shouldn't we therefore revalidate AMO_HWAD cap for domains with
> dirty_ops and reject this combination?
> 
> FYI, both AMD and Intel have attach-time dirty-tracking checks. See
> drivers/iommu/intel/iommu.c:3195 and drivers/iommu/amd/iommu.c:3221.

Right, need to check on every domain attach that the domain is
compatible with the iommu instance.

Jason