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

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On 2022/5/17 下午4:55, Yi Liu wrote:
Hi Zhangfei,

On 2022/5/12 17:01, zhangfei.gao@xxxxxxxxxxx wrote:

Hi, Yi

On 2022/5/11 下午10:17, zhangfei.gao@xxxxxxxxxxx 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@xxxxxxxxx/

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
Then how to get hwpt_id in map/unmap_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)


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.

The iommufd_hw_pagetable_from_id can be used for
1, allocate domain, which need para dev
case IOMMUFD_OBJ_IOAS
hwpt = iommufd_hw_pagetable_auto_get(ictx, ioas, dev);

2. Just return allocated domain via hwpt_id, which does not need dev.
case IOMMUFD_OBJ_HW_PAGETABLE:
return container_of(obj, struct iommufd_hw_pagetable, obj);

By the way, any plan of the nested mode?

Thanks



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