Re: [RFC 00/18] vfio: Adopt iommufd

[Yi Liu]

Hi Zhangfei,

On 2022/5/12 17:01, zhangfei.gao@foxmail.com wrote:
> Hi, Yi
>
> On 2022/5/11 下午10:17, zhangfei.gao@foxmail.com wrote:
> > On 2022/5/10 下午10:08, Yi Liu wrote:
> > > On 2022/5/10 20:45, Jason Gunthorpe wrote:
> > > > On Tue, May 10, 2022 at 08:35:00PM +0800, Zhangfei Gao wrote:
> > > > > Thanks Yi and Eric,
> > > > > Then will wait for the updated iommufd kernel for the PCI MMIO region.
> > > > >
> > > > > Another question,
> > > > > How to get the iommu_domain in the ioctl.
> > > >
> > > > The ID of the iommu_domain (called the hwpt) it should be returned by
> > > > the vfio attach ioctl.
> > >
> > > yes, hwpt_id is returned by the vfio attach ioctl and recorded in
> > > qemu. You can query page table related capabilities with this id.
> > >
> > > https://lore.kernel.org/kvm/20220414104710.28534-16-yi.l.liu@intel.com/
> > Thanks Yi,
> >
> > Do we use iommufd_hw_pagetable_from_id in kernel?
> >
> > The qemu send hwpt_id via ioctl.
> > Currently VFIOIOMMUFDContainer has hwpt_list,
> > Which member is good to save hwpt_id, IOMMUTLBEntry?
>
> Can VFIOIOMMUFDContainer  have multi hwpt?

yes, it is possible

> Since VFIOIOMMUFDContainer has hwpt_list now.
> If so, how to get specific hwpt from map/unmap_notify in hw/vfio/as.c, 
> where no vbasedev can be used for compare.
>
> I am testing with a workaround, adding VFIOIOASHwpt *hwpt in 
> VFIOIOMMUFDContainer.
> And save hwpt when vfio_device_attach_container.
>
> > In kernel ioctl: iommufd_vfio_ioctl
> > @dev: Device to get an iommu_domain for
> > iommufd_hw_pagetable_from_id(struct iommufd_ctx *ictx, u32 pt_id, struct 
> > device *dev)
> > But iommufd_vfio_ioctl seems no para dev?
>
> We can set dev=Null since IOMMUFD_OBJ_HW_PAGETABLE does not need dev.
> iommufd_hw_pagetable_from_id(ictx, hwpt_id, NULL)

this is not good. dev is passed in to this function to allocate domain
and also check sw_msi things. If you pass in a NULL, it may even unable
to get a domain for the hwpt. It won't work I guess.

> Thanks
> >

--
Regards,
Yi Liu