Re: [RFC PATCH v2 09/20] hw/arm/smmuv3-accel: Add set/unset_iommu_device callback

[Nicolin Chen <nicolinc@nvidia.com>]

On Mon, Mar 17, 2025 at 08:38:23AM +0000, Shameerali Kolothum Thodi wrote:
> Hi Nicolin,
> 
> > -----Original Message-----
> > From: Nicolin Chen <nicolinc@nvidia.com>
> > Sent: Tuesday, March 11, 2025 9:08 PM
> > To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>
> > Cc: qemu-arm@nongnu.org; qemu-devel@nongnu.org;
> > eric.auger@redhat.com; peter.maydell@linaro.org; jgg@nvidia.com;
> > ddutile@redhat.com; berrange@redhat.com; nathanc@nvidia.com;
> > mochs@nvidia.com; smostafa@google.com; Linuxarm
> > <linuxarm@huawei.com>; Wangzhou (B) <wangzhou1@hisilicon.com>;
> > jiangkunkun <jiangkunkun@huawei.com>; Jonathan Cameron
> > <jonathan.cameron@huawei.com>; zhangfei.gao@linaro.org
> > Subject: Re: [RFC PATCH v2 09/20] hw/arm/smmuv3-accel: Add
> > set/unset_iommu_device callback
> > 
> > On Tue, Mar 11, 2025 at 02:10:34PM +0000, Shameer Kolothum wrote:
> > > @@ -30,6 +32,185 @@ static SMMUv3AccelDevice
> > *smmuv3_accel_get_dev(SMMUState *s, SMMUPciBus *sbus,
> > >      return accel_dev;
> > >  }
> > >
> > > +static bool
> > > +smmuv3_accel_dev_attach_viommu(SMMUv3AccelDevice *accel_dev,
> > > +                               HostIOMMUDeviceIOMMUFD *idev, Error **errp)
> > 
> > With vEVENTQ v9, vDEVICE (vSID) is required to attach a device
> > to a proxy NESTED hwpt (applicable to bypass/abort HWPTs too).
> > So, host_iommu_device_iommufd_attach_hwpt() would fail in this
> > function because vSID isn't ready at this stage. So all those
> > calls should be moved out of the function, then this should be
> > likely "smmuv3_accel_dev_alloc_viommu"?
> > 
> > That being said, I don't know when QEMU actually prepare a BDF
> > number for a vfio-pci device. The only place that I see it is
> > ready is at guest-level SMMU installing the Stream Table, i.e.
> > in smmuv3_accel_install_nested_ste().

> > > +    /*
> > > +     * Attach the bypass STE which means S1 bypass and S2 translate.
> > > +     * This is to make sure that the vIOMMU object is now associated
> > > +     * with the device and has this STE installed in the host SMMUV3.
> > > +     */
> > > +    if (!host_iommu_device_iommufd_attach_hwpt(
> > > +                idev, viommu->bypass_hwpt_id, errp)) {
> > > +        error_report("failed to attach the bypass pagetable");
> > > +        goto free_bypass_hwpt;
> > > +    }
> > 
> > Ditto. We have to postpone this until vdevice is allocated.
> 
> Ok.  I will take a look based on the  vEVENTQ v9 series.
> I guess this Qemu branch of yours is a more representative of the changes described
> above?
> https://github.com/nicolinc/qemu/commits/wip/for_iommufd_veventq-v9/

Yes. 

Mainly this change:
https://github.com/nicolinc/qemu/commit/d8f496eaf528f1c397f2374a999b8b23fd55c75b

Thanks
Nicolin