Re: [RFC PATCH 5/5] hw/arm/virt-acpi-build: Add IORT RMR regions to handle MSI nested binding

[Jason Gunthorpe <jgg@nvidia.com>]

On Tue, Dec 10, 2024 at 05:28:17PM -0800, Nicolin Chen wrote:
> > I would ideally turn it around and provide that range information to
> > the kernel and totally ignore the SW_MSI reserved region once
> > userspace provides it.
> 
> Hmm.. that sounds like a uAPI for vITS range..but yes..

It controls the window that the kernel uses to dynamically map the ITS
pages.

> So, VMM can GET_OPTION(SW_MSI) for msi_base to extract the
> info from kernel. Likely need a second call for its length?
> Since IOMMU_OPTION only supports one val64 input or output.

No, just forget about the kernel's SW_MSI region. The VMM uses this
API and overrides it and iommufd completely ignores SW_MSI.

There is nothing special about the range hard coded into the smmu
driver.

Jason