Hi,
On 1/31/25 4:23 PM, Shameerali Kolothum Thodi wrote: > >> -----Original Message----- >> From: Jason Gunthorpe <j...@nvidia.com> >> Sent: Friday, January 31, 2025 2:54 PM >> To: Shameerali Kolothum Thodi <shameerali.kolothum.th...@huawei.com> >> Cc: Daniel P. Berrangé <berra...@redhat.com>; qemu-...@nongnu.org; >> qemu-devel@nongnu.org; eric.au...@redhat.com; >> peter.mayd...@linaro.org; nicol...@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; Nathan Chen <nath...@nvidia.com> >> Subject: Re: [RFC PATCH 0/5] hw/arm/virt: Add support for user-creatable >> nested SMMUv3 >> >> On Fri, Jan 31, 2025 at 02:39:53PM +0000, Shameerali Kolothum Thodi >> wrote: >> >>>>> And Qemu does some checking to make sure that the device is indeed >>>> associated >>>>> with the specified phys-smmuv3. This can be done going through the >>>> sysfs path checking >>>>> which is what I guess libvirt is currently doing to populate the >> topology. >>>> So basically >>>>> Qemu is just replicating that to validate again. >>>> I would prefer that iommufd users not have to go out to sysfs.. >>>> >>>>> Or another option is extending the IOMMU_GET_HW_INFO IOCTL to >>>> return the phys >>>>> smmuv3 base address which can avoid going through the sysfs. >>>> It also doesn't seem great to expose a physical address. But we could >>>> have an 'iommu instance id' that was a unique small integer? >>> Ok. But how the user space can map that to the device? >> Why does it need to? >> >> libvirt picks some label for the vsmmu instance, it doesn't matter >> what the string is. >> >> qemu validates that all of the vsmmu instances are only linked to PCI >> device that have the same iommu ID. This is already happening in the >> kernel, it will fail attaches to mismatched instances. >> >> Nothing further is needed? > -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-accel,bus=pcie.1,id=smmuv1 \ I don't get what is the point of adding such an id if it is not referenced anywhere? Eric > -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-accel,pci-bus=pcie.2,id=smmuv2 \ > -device vfio-pci,host=0000:75:00.1,bus=pcie.port2,iommufd=iommufd0 \ > > I think it works from a functionality point of view. A particular > instance of arm-smmuv3-accel(say id=smmuv1) can only have devices attached > to the same phys smmuv3 "iommu instance id" > > But not sure from a libvirt/Qemu interface point of view[0] the concerns > are addressed. Daniel/Nathan? > > Thanks, > Shameer > https://lists.libvirt.org/archives/list/de...@lists.libvirt.org/message/X6R52JRBYDFZ5PSJFR534A655UZ3RHKN/ >
