On Sat, 8 Feb 2020 at 12:01, Eric Auger <eric.au...@redhat.com> wrote: > > Adds the "virtio,pci-iommu" node in the host bridge node and > the RID mapping, excluding the IOMMU RID. > > This is done in the virtio-iommu-pci hotplug handler which > gets called only if no firmware is loaded or if -no-acpi is > passed on the command line. As non DT integration is > not yet supported by the kernel we must make sure we > are in DT mode. This limitation will be removed as soon > as the topology description feature gets supported. > > Signed-off-by: Eric Auger <eric.au...@redhat.com> > > +static void create_virtio_iommu(VirtMachineState *vms, Error **errp) > +{ > + const char compat[] = "virtio,pci-iommu"; > + uint16_t bdf = vms->virtio_iommu_bdf; > + char *node; > + > + vms->iommu_phandle = qemu_fdt_alloc_phandle(vms->fdt); > + > + node = g_strdup_printf("%s/virtio_iommu@%d", vms->pciehb_nodename, bdf); > + qemu_fdt_add_subnode(vms->fdt, node); > + qemu_fdt_setprop(vms->fdt, node, "compatible", compat, sizeof(compat)); > + qemu_fdt_setprop_sized_cells(vms->fdt, node, "reg", > + 1, bdf << 8, 1, 0, 1, 0, > + 1, 0, 1, 0); > + > + qemu_fdt_setprop_cell(vms->fdt, node, "#iommu-cells", 1); > + qemu_fdt_setprop_cell(vms->fdt, node, "phandle", vms->iommu_phandle); > + g_free(node); > + > + qemu_fdt_setprop_cells(vms->fdt, vms->pciehb_nodename, "iommu-map", > + 0x0, vms->iommu_phandle, 0x0, bdf, > + bdf + 1, vms->iommu_phandle, bdf + 1, 0xffff - > bdf); > +}
This function name implies that we're creating the IOMMU device here (which would be a weird thing to do in a hotplug callback for some other device), but it looks like we're only adding device tree nodes ? Given that we write the FDT blob into the guest RAM on bootup, how does making changes to it here on hotplug (which I assume to be 'after boot, whenever the user hot-plugs something') work? thanks -- PMM