RE: [RFC PATCH 0/5] hw/arm/virt: Add support for user-creatable nested SMMUv3

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

> -----Original Message-----
> From: Nicolin Chen <nicolinc@nvidia.com>
> Sent: Tuesday, November 12, 2024 11:00 PM
> To: Shameerali Kolothum Thodi
> <shameerali.kolothum.thodi@huawei.com>; nathanc@nvidia.com
> Cc: qemu-arm@nongnu.org; qemu-devel@nongnu.org;
> eric.auger@redhat.com; peter.maydell@linaro.org; jgg@nvidia.com;
> ddutile@redhat.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 0/5] hw/arm/virt: Add support for user-creatable
> nested SMMUv3
> 
> On Fri, Nov 08, 2024 at 12:52:37PM +0000, Shameer Kolothum wrote:
> > Few ToDos to note,
> > 1. At present default-bus-bypass-iommu=on should be set when
> >    arm-smmuv3-nested dev is specified. Otherwise you may get an IORT
> >    related boot error.  Requires fixing.
> > 2. Hot adding a device is not working at the moment. Looks like pcihp irq
> issue.
> >    Could be a bug in IORT id mappings.
> 
> Do we have enough bus number space for each pbx bus in IORT?
> 
> The bus range is defined by min_/max_bus in hort_host_bridges(),
> where the pci_bus_range() function call might not leave enough
> space in the range for hotplugs IIRC.

Ok. Thanks for the pointer. I will debug that.

> > ./qemu-system-aarch64 -machine virt,gic-version=3,default-bus-bypass-
> iommu=on \
> > -enable-kvm -cpu host -m 4G -smp cpus=8,maxcpus=8 \
> > -object iommufd,id=iommufd0 \
> > -bios QEMU_EFI.fd \
> > -kernel Image \
> > -device virtio-blk-device,drive=fs \
> > -drive if=none,file=rootfs.qcow2,id=fs \
> > -device pxb-pcie,id=pcie.1,bus_nr=8,bus=pcie.0 \
> > -device pcie-root-port,id=pcie.port1,bus=pcie.1,chassis=1 \
> > -device arm-smmuv3-nested,id=smmuv1,pci-bus=pcie.1 \
> > -device vfio-pci,host=0000:7d:02.1,bus=pcie.port1,iommufd=iommufd0 \
> > -device pxb-pcie,id=pcie.2,bus_nr=16,bus=pcie.0 \
> > -device pcie-root-port,id=pcie.port2,bus=pcie.2,chassis=2 \
> > -device arm-smmuv3-nested,id=smmuv2,pci-bus=pcie.2 \
> > -device vfio-pci,host=0000:75:00.1,bus=pcie.port2,iommufd=iommufd0 \
> > -append "rdinit=init console=ttyAMA0 root=/dev/vda2 rw
> earlycon=pl011,0x9000000" \
> > -device virtio-9p-pci,fsdev=p9fs2,mount_tag=p9,bus=pcie.0 \
> > -fsdev local,id=p9fs2,path=p9root,security_model=mapped \
> > -net none \
> > -nographic
> ..
> > With a pci topology like below,
> > [root@localhost ~]# lspci -tv
> > -+-[0000:00]-+-00.0  Red Hat, Inc. QEMU PCIe Host bridge
> >  |           +-01.0  Red Hat, Inc. QEMU PCIe Expander bridge
> >  |           +-02.0  Red Hat, Inc. QEMU PCIe Expander bridge
> >  |           \-03.0  Virtio: Virtio filesystem
> >  +-[0000:08]---00.0-[09]----00.0  Huawei Technologies Co., Ltd. HNS
> Network Controller (Virtual Function)
> >  \-[0000:10]---00.0-[11]----00.0  Huawei Technologies Co., Ltd. HiSilicon ZIP
> Engine(Virtual Function)
> > [root@localhost ~]#
> >
> > And if you want to add another HNS VF, it should be added to the same
> SMMUv3
> > as of the first HNS dev,
> >
> > -device pcie-root-port,id=pcie.port3,bus=pcie.1,chassis=3 \
> > -device vfio-pci,host=0000:7d:02.2,bus=pcie.port3,iommufd=iommufd0 \
> ..
> > At present Qemu is not doing any extra validation other than the above
> > failure to make sure the user configuration is correct or not. The
> > assumption is libvirt will take care of this.
> 
> Nathan from NVIDIA side is working on the libvirt. And he already
> did some prototype coding in libvirt that could generate required
> PCI topology. I think he can take this patches for a combined test.

Cool. That's good to know.

Thanks,
SHameer