Hi Liu, On 4/25/19 9:12 AM, Liu, Yi L wrote: > Hi Eric, > >> From: Auger Eric [mailto:eric.au...@redhat.com] >> Sent: Thursday, April 25, 2019 1:28 AM >> To: Jacob Pan <jacob.jun....@linux.intel.com>; >> iommu@lists.linux-foundation.org; >> 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 <baolu...@linux.intel.com> >>> >>> 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."
OK I understand. But strictly speaking a vIOMMU may not implement CM. But that's nitpicking ;-) Thanks Eric > > Thanks, > Yi Liu > _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
