Re: [PATCH v3 0/6] intel_iommu: Enable PRQ support for passthrough device

Hi Zhenzhong,

I will read this series early next week.
thanks for the respin!

btw, related to this work: have ever seen
vfio_device_get_aw_bits returning 47 whereas
the iommu supports 48? This leads the following
aw test to fail:

```
ret = hiodc->get_cap(hiod, HOST_IOMMU_DEVICE_CAP_AW_BITS, errp);
if (ret < 0) {
    return false;
}
if (s->aw_bits > ret) {
    error_setg(errp, "aw-bits %d > host aw-bits %d", s->aw_bits, ret);
    return false;
}
```

I got this when trying to nest VMs.

On Thu, 2026-08-06 at 03:38 -0400, Zhenzhong Duan wrote:
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> 
> 
> Hi,
> 
> When svm=on,pasid-bits=N,fsts=on is configured for virtual vtd, we enable  
> guest's support for vSVM. In this case, the host VTD may generate  
> recoverable first stage page fault event, QEMU read the event and inject  
> it to guest.
> 
> After guest handles the event, it sends a page group response, QEMU gets  
> the response and pass it to host VTD.
> 
> This series adds QEMU support for receiving such host events through the  
> FAULTQ interface and propagating them to the guest, then catching guest's  
> responses and propagating them to host.
> 
> GIT branch: [https://github.com/yiliu1765/qemu/tree/zhenzhong/iommufd_prq.v3](https://github.com/yiliu1765/qemu/tree/zhenzhong/iommufd_prq.v3)
> 
> Tests:  
> Tested with DSA wq attached to an user app which triggers IO page fault on  
> process page table durging DMA.
> 
> Thanks  
> Zhenzhong
> 
> Changelog:  
> v3:  
> - convert to PCI pasid before passing to vtd_pri_request_page (Clement)  
> - expose vtd_pri_request_page and drop accel_ops pointer (Clement)  
> - add a cleanup patch "intel_iommu_accel: Guard VTDAccelPASIDCacheEntry definition" (Philippe)
> 
> v2:  
> - define fault_fd int type (Liuyi)  
> - update comments on FAULTQ_BUF_SIZE (Liuyi)  
> - drop param vtd_hiod in vtd_destroy_old_fs_faultq() (Liuyi)  
> - s/vtd_propagate_page_group_response_accel/vtd_accel_propagate_page_group_response (Liuyi)  
> - call vtd_prq_response_notify() directly instead of through pri_notifier (Liuyi)  
> - replace "fault_id != 0" check with "fault_fd < 0" check (Liuyi)
> 
> 
> Zhenzhong Duan (6):  
>   intel_iommu_accel: Guard VTDAccelPASIDCacheEntry definition  
>   backends/iommufd: Introduce iommufd_backend_alloc_faultq  
>   backends/iommufd: Extend iommufd_backend_alloc_hwpt() with fault_id  
>   intel_iommu_accel: Add PRQ injection for passthrough device  
>   intel_iommu_accel: Accept PRQ response for passthrough device  
>   intel_iommu_accel: teardown FAULTQ resources in bottom half
> 
>  hw/i386/intel_iommu_accel.h    |  16 ++-  
>  hw/i386/intel_iommu_internal.h |   3 +  
>  include/hw/i386/intel_iommu.h  |   6 +  
>  include/system/iommufd.h       |   7 +-  
>  backends/iommufd.c             |  28 +++-  
>  hw/arm/smmuv3-accel.c          |   6 +-  
>  hw/i386/intel_iommu.c          |  11 +-  
>  hw/i386/intel_iommu_accel.c    | 245 ++++++++++++++++++++++++++++++++-  
>  hw/vfio/iommufd.c              |   2 +-  
>  backends/trace-events          |   3 +-  
>  hw/i386/trace-events           |   2 +  
>  11 files changed, 308 insertions(+), 21 deletions(-)
> 
> --  
> 2.52.0
>