Hi Eric, > From: Auger Eric [mailto:[email protected]] > Sent: Thursday, April 25, 2019 1:28 AM > To: Jacob Pan <[email protected]>; > [email protected]; > Subject: Re: [PATCH v2 09/19] iommu/vt-d: Enlightened PASID allocation > > Hi Jacob, > > On 4/24/19 1:31 AM, Jacob Pan wrote: > > From: Lu Baolu <[email protected]> > > > > If Intel IOMMU runs in caching mode, a.k.a. virtual IOMMU, the IOMMU > > driver should rely on the emulation software to allocate and free > > PASID IDs. > Do we make the decision depending on the CM or depending on the VCCAP_REG? > > VCCAP_REG description says: > > If Set, software must use Virtual Command Register interface to allocate and > free > PASIDs.
The answer is it depends on the ECAP.VCS and then the PASID allocation bit in VCCAP_REG. But VCS bit implies the iommu is a software implementation (vIOMMU) of vt-d architecture. Pls refer to the descriptions of "Virtual Command Support" in vt-d 3.0 spec. "Hardware implementations of this architecture report a value of 0 in this field. Software implementations (emulation) of this architecture may report VCS=1." Thanks, Yi Liu _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
