RE: [PATCH v5 00/11] hw/arm/virt: Add support for user creatable SMMUv3 device

[Shameerali Kolothum Thodi via <qemu-devel@nongnu.org>]

> -----Original Message-----
> From: Nathan Chen <nathanc@nvidia.com>
> Sent: Wednesday, July 2, 2025 2:02 AM
> To: qemu-devel@nongnu.org
> Cc: berrange@redhat.com; ddutile@redhat.com; eric.auger@redhat.com;
> gustavo.romero@linaro.org; imammedo@redhat.com; jgg@nvidia.com;
> jiangkunkun <jiangkunkun@huawei.com>; Jonathan Cameron
> <jonathan.cameron@huawei.com>; Linuxarm <linuxarm@huawei.com>;
> mochs@nvidia.com; nathanc@nvidia.com; nicolinc@nvidia.com;
> peter.maydell@linaro.org; qemu-arm@nongnu.org; Shameerali Kolothum
> Thodi <shameerali.kolothum.thodi@huawei.com>; smostafa@google.com;
> Wangzhou (B) <wangzhou1@hisilicon.com>; zhangfei.gao@linaro.org
> Subject: Re: [PATCH v5 00/11] hw/arm/virt: Add support for user creatable
> SMMUv3 device
> 
> >    To address this, patch #6 in the series introduces a new helper
> >    function pci_setup_iommu_per_bus(), which explicitly sets the
> >    iommu_per_bus field in the PCIBus structure. This allows
> >    pci_device_get_iommu_bus_devfn() to retrieve IOMMU ops based
> >    on the specific bus.
> >
> >    This patch series introduces support for a user-creatable SMMUv3
> device
> >    (-device arm-smmuv3) in QEMU.
> 
> Tested-by: Nathan Chen <nathanc@nvidia.com>
> 
> I re-ran the test from v3 [0] and am able to create 16 SMMUv3 devices in
> a qemu VM with emulated devices properly associated with the guest
> SMMUs
> in guest sysfs - verified with some guest SMMUs having two or three
> emulated NICs assigned to them while other guest SMMUs have a minimum
> of
> one assigned.
> 
> Removing SMMUv3 devices from the VM config described above, I do not
> observe the problematic behavior where devices behind PXBs without
> SMMUs
> erroneously use the address space from pcie.0's SMMU. I removed SMMUv3
> devices from PXBs with one, two, and three emulated NICs assigned to
> them. Below are the guest topology and qemu command used where
> SMMUv3
> devices are excluded from the original test:

Cool. Appreciate testing that specifically.

Thanks,
Shameer