Re: [PATCH] driver core: platform: expose numa_node to users in sysfs

[Greg KH]

On Tue, Jun 02, 2020 at 05:09:57AM +0000, Song Bao Hua (Barry Song) wrote:
> > >
> > > Platform devices are NUMA?  That's crazy, and feels like a total abuse
> > > of platform devices and drivers that really should belong on a "real"
> > > bus.
> > 
> > I am not sure if it is an abuse of platform device. But smmu is a platform
> > device,
> > drivers/iommu/arm-smmu-v3.c is a platform driver.
> > In a typical ARM server, there are maybe multiple SMMU devices which can
> > support
> > IO virtual address and page tables for other devices on PCI-like busses.
> > Each different SMMU device might be close to different NUMA node. There is
> > really a hardware topology.
> > 
> > If you have multiple CPU packages in a NUMA server, some platform devices
> > might
> > Belong to CPU0, some other might belong to CPU1.
> 
> Those devices are populated by acpi_iort for an ARM server:
> 
> drivers/acpi/arm64/iort.c:
> 
> static const struct iort_dev_config iort_arm_smmu_v3_cfg __initconst = {
>         .name = "arm-smmu-v3",
>         .dev_dma_configure = arm_smmu_v3_dma_configure,
>         .dev_count_resources = arm_smmu_v3_count_resources,
>         .dev_init_resources = arm_smmu_v3_init_resources,
>         .dev_set_proximity = arm_smmu_v3_set_proximity,
> };
> 
> void __init acpi_iort_init(void)
> {
>         acpi_status status;
> 
>         status = acpi_get_table(ACPI_SIG_IORT, 0, &iort_table);
>         ...
>         iort_check_id_count_workaround(iort_table);
>         iort_init_platform_devices();
> }
> 
> static void __init iort_init_platform_devices(void)
> {
>         ...
> 
>         for (i = 0; i < iort->node_count; i++) {
>                 if (iort_node >= iort_end) {
>                         pr_err("iort node pointer overflows, bad table\n");
>                         return;
>                 }
> 
>                 iort_enable_acs(iort_node);
> 
>                 ops = iort_get_dev_cfg(iort_node);
>                 if (ops) {
>                         fwnode = acpi_alloc_fwnode_static();
>                         if (!fwnode)
>                                 return;
> 
>                         iort_set_fwnode(iort_node, fwnode);
> 
>                         ret = iort_add_platform_device(iort_node, ops);
>                         if (ret) {
>                                 iort_delete_fwnode(iort_node);
>                                 acpi_free_fwnode_static(fwnode);
>                                 return;
>                         }
>                 }
> 
>                 ...
>         }
> ...
> }
> 
> NUMA node is got from ACPI:
> 
> static int  __init arm_smmu_v3_set_proximity(struct device *dev,
>                                               struct acpi_iort_node *node)
> {
>         struct acpi_iort_smmu_v3 *smmu;
> 
>         smmu = (struct acpi_iort_smmu_v3 *)node->node_data;
>         if (smmu->flags & ACPI_IORT_SMMU_V3_PXM_VALID) {
>                 int dev_node = acpi_map_pxm_to_node(smmu->pxm);
> 
>                 ...
> 
>                 set_dev_node(dev, dev_node);
>                 ...
>         }
>         return 0;
> }
> 
> Barry

That's fine, but those are "real" devices, not platform devices, right?

What platform device has this issue?  What one will show up this way
with the new patch?

thanks,

greg k-h