Re: [PATCH v2] vhost/vdpa: Add MSI translation tables to iommu for software-managed MSI

[Michael S. Tsirkin]

On Thu, Feb 16, 2023 at 08:14:50PM -0400, Jason Gunthorpe wrote:
> On Tue, Feb 07, 2023 at 08:08:43PM +0800, Nanyong Sun wrote:
> > From: Rong Wang <wangrong68@xxxxxxxxxx>
> > 
> > Once enable iommu domain for one device, the MSI
> > translation tables have to be there for software-managed MSI.
> > Otherwise, platform with software-managed MSI without an
> > irq bypass function, can not get a correct memory write event
> > from pcie, will not get irqs.
> > The solution is to obtain the MSI phy base address from
> > iommu reserved region, and set it to iommu MSI cookie,
> > then translation tables will be created while request irq.
> 
> Probably not what anyone wants to hear, but I would prefer we not add
> more uses of this stuff. It looks like we have to get rid of
> iommu_get_msi_cookie() :\
> 
> I'd like it if vdpa could move to iommufd not keep copying stuff from
> it..

Absolutely but when is that happening?

> Also the iommu_group_has_isolated_msi() check is missing on the vdpa
> path, and it is missing the iommu ownership mechanism.
> 
> Also which in-tree VDPA driver that uses the iommu runs on ARM? Please
> don't propose core changes for unmerged drivers. :(
> 
> Jason