On Fri, Nov 22, 2024 at 05:38:54PM +0000, Shameerali Kolothum Thodi via wrote: > > > > -----Original Message----- > > From: Nathan Chen <nath...@nvidia.com> > > Sent: Friday, November 22, 2024 1:42 AM > > To: Shameerali Kolothum Thodi <shameerali.kolothum.th...@huawei.com> > > Cc: qemu-...@nongnu.org; qemu-devel@nongnu.org; > > eric.au...@redhat.com; peter.mayd...@linaro.org; j...@nvidia.com; > > ddut...@redhat.com; Linuxarm <linux...@huawei.com>; Wangzhou (B) > > <wangzh...@hisilicon.com>; jiangkunkun <jiangkun...@huawei.com>; > > Jonathan Cameron <jonathan.came...@huawei.com>; > > zhangfei....@linaro.org; Nicolin Chen <nicol...@nvidia.com> > > Subject: Re: [RFC PATCH 0/5] hw/arm/virt: Add support for user-creatable > > nested SMMUv3 > > > > >> Also as a heads up, I've added support for auto-inserting PCIe switch > > >> between the PXB and GPUs in libvirt to attach multiple devices to a > > SMMU > > >> node per libvirt's documentation - "If you intend to plug multiple > > >> devices into a pcie-expander-bus, you must connect a > > >> pcie-switch-upstream-port to the pcie-root-port that is plugged into the > > >> pcie-expander-bus, and multiple pcie-switch-downstream-ports to the > > >> pcie-switch-upstream-port". Future unit-tests should follow this > > >> topology configuration. > > > > > > Ok. Could you please give me an example Qemu equivalent command > > option, > > > if possible, for the above case. I am not that familiar with libvirt > > and I would > > > also like to test the above scenario. > > > > You can use "-device x3130-upstream" for the upstream switch port, and > > "-device xio3130-downstream" for the downstream port: > > > > -device pxb-pcie,bus_nr=250,id=pci.1,bus=pcie.0,addr=0x1 \ > > -device pcie-root-port,id=pci.2,bus=pci.1,addr=0x0 \ > > -device x3130-upstream,id=pci.3,bus=pci.2,addr=0x0 \ > > -device xio3130- > > downstream,id=pci.4,bus=pci.3,addr=0x0,chassis=17,port=1 \ > > -device vfio-pci,host=0009:01:00.0,id=hostdev0,bus=pci.4,addr=0x0 \ > > -device arm-smmuv3-nested,pci-bus=pci.1 > > Thanks. Just wondering why libvirt mandates usage of pcie-switch for multiple > device plugging rather than just using pcie-root-ports?
Libvirt does not rquire use of pcie-switch. It supports them, but in the absence of app requested configs, libvirt will always just populate pcie-root-port devices. switches are something that has to be explicitly asked for, and I don't see much need todo that. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
