On Wed, Jun 28, 2023 at 02:47:02AM +0000, Tian, Kevin wrote: > > From: Jason Gunthorpe <jgg@xxxxxxxxxx> > > Sent: Wednesday, June 28, 2023 12:01 AM > > > > On Tue, Jun 27, 2023 at 06:02:13AM +0000, Tian, Kevin wrote: > > > > From: Nicolin Chen <nicolinc@xxxxxxxxxx> > > > > Sent: Tuesday, June 27, 2023 1:29 AM > > > > > > > > > I'm not sure whether the MSI region needs a special MSI type or > > > > > just a general RESV_DIRECT type for 1:1 mapping, though. > > > > > > > > I don't quite get this part. Isn't MSI having IOMMU_RESV_MSI > > > > and IOMMU_RESV_SW_MSI? Or does it juset mean we should report > > > > the iommu_resv_type along with reserved regions in new ioctl? > > > > > > > > > > Currently those are iommu internal types. When defining the new > > > ioctl we need think about what are necessary presenting to the user. > > > > > > Probably just a list of reserved regions plus a flag to mark which > > > one is SW_MSI? Except SW_MSI all other reserved region types > > > just need the user to reserve them w/o knowing more detail. > > > > I think I prefer the idea we just import the reserved regions from a > > devid and do not expose any of this detail to userspace. > > > > Kernel can make only the SW_MSI a mandatory cut out when the S2 is > > attached. > > > > I'm confused. > > The VMM needs to know reserved regions per dev_id and report them > to the guest. > > And we have aligned on that reserved regions (except SW_MSI) should > not be automatically added to S2 in nesting case. Then the VMM cannot > rely on IOAS_IOVA_RANGES to identify the reserved regions. We also said we need a way to load the reserved regions to create an identity compatible version of the HWPT So we have a model where the VMM will want to load in regions beyond the currently attached device needs > So there needs a new interface for the user to discover reserved regions > per dev_id, within which the SW_MSI region should be marked out so > identity mapping can be installed properly for it in S1. > > Did I misunderstand your point in previous discussion? This is another discussion, if the vmm needs this then we probably need a new API to get it. Jason
