Re: [PATCH v2 00/11] iommufd: Add nesting infrastructure

[Jason Gunthorpe]

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.

Jason