> From: Jason Gunthorpe <jgg@xxxxxxxxxx> > Sent: Thursday, May 23, 2024 11:01 PM > > On Thu, May 23, 2024 at 06:19:59AM +0000, Tian, Kevin wrote: > > > From: Jason Gunthorpe <jgg@xxxxxxxxxx> > > > Sent: Wednesday, May 22, 2024 2:25 AM > > > > > > On Tue, May 14, 2024 at 06:59:07PM -0700, Nicolin Chen wrote: > > > > So, you want a proxy S1 domain for a device to attach, in case > > > > of a stage-2 only setup, because an S2 domain will no longer has > > > > a VMID, since it's shared among viommus. In the SMMU driver case, > > > > an arm_smmu_domain won't have an smmu pointer, so a device can't > > > > attach to an S2 domain but always an nested S1 domain, right? > > > > > > That seems like a simple solution to the VMID lifetime, but it means > > > the kernel has to decode more types of vSTE. > > > > > > > why does ATC invalidation need to know about VMID? > > ATC invalidation always requires a vRID to pRID translation and the > VIOMMU will hold that translation. > > On vCMDQ HW and on AMD HW the vRID to pRID translation is pushed into > HW, and vCMDQ requires the VMID to do that. > At a quick glance VMID and vRID->pRID translation are both configurations of a vintf. My impression was that vintf->vmid is added to guest cmd when it's about iotlb invalidation. then vintf->sid_slots is walked when handling a guest cmd for ATC invalidation. I'm not sure why the latter one requires a valid VMID to do the walking except it's a implementation choice made by vCMDQ?
