Re: [PATCH RFCv2 09/13] iommufd: Add IOMMU_OPTION_SW_MSI_START/SIZE ioctls

[Jason Gunthorpe]

On Wed, Jan 29, 2025 at 06:49:22PM +0100, Eric Auger wrote:
> > If it was overriden inside iommufd then the user told the kernel what
> > range to use to override it. I don't need to go back and report back
> > to userspace information that it already gave to the kernel..
> 
> Looks strange to me because info exposed in sysfs is wrong then. What if
> someone else relies on this info, either at kernel level through the
> get_resv_regions callback or from user space.

Nothing else should call get_resv_regions() because VFIO is bound to
the device and iommufd owns the domain. We expect some exclusivity
here :)

sysfs for sw_msi should be understood as reporting the driver
recommendation, not anything to do with the current MSI operation of
the device.

Jason