Hi Kelly, On Fri, Feb 26, 2016 at 07:16:29PM +0000, Zytaruk, Kelly wrote: > I applied the fix and the WARN on ats_enabled flag goes away. The > detach_device() gets called against the correct dev when > pci_sriov_disable is called. This looks like it is fixed. Great, thanks for testing. I'll send the patch upstream so that it gets included into v4.5 > I have a couple questions; > > 1) find_dev_data() > I put some printk statements into the enable and disable path for > iommu. On the first enable in find_dev_data() I see the following. > Note that the archdata.iommu data area does not exist and must be > initialized; > > [ 2237.701423] pci_device_add - call device_add for base device 0000:02:00.0 dev->ats_enabled = 0 > [ 2237.701555] vgaarb: device added: PCI:0000:02:00.0,decodes=io+mem,owns=none,locks=none > [ 2237.701560] iommu_init_device - find archdata.iommu for dev 0000:02:00.0, device id = 512 > [ 2237.701565] find_dev_data - no archdata.iommu for devid 512, allocate a new one > [ 2237.701568] find_dev_data - devid 512 not attached to domain > > One the second enable (after a disable) find_dev_data() finds and reuses the previous archdata.iommu as shown below. > > [ 2316.549788] pci_device_add - call device_add for base device 0000:02:00.0 dev->ats_enabled = 0 > [ 2316.549931] vgaarb: device added: PCI:0000:02:00.0,decodes=io+mem,owns=none,locks=none > [ 2316.549936] iommu_init_device - find archdata.iommu for dev 0000:02:00.0, device id = 512 > [ 2316.549942] find_dev_data - found an existing archdata.iommu for devid 512 > [ 2316.549944] find_dev_data - devid 512 not attached to domain > > Since the second enable is reusing the archdata.iommu from the first > enable is there any further cleanup that would need to be done to the > archdata.iommu data area? Possibly yes, I need to have a closer look there. That caching of dev_data structures is done for historical reasons. I'll check first if this is still necessary. > What is this area used for? I understand that archdata is platform > specific but what does iommu use it for, is there a good document that > describes its use or do I have to read through the source code? > How can I test to ensure that it is properly reused and has proper > data integrity? There are no documents about the inner structure of the AMD IOMMU driver besides the source code. The dev_data area is used to attach iommu-driver specific data (like the domain it is attached to) to a struct device. > > 2) What is "dev_data->domain" and "group" in relation to iommu. I > tried google and came up with meaningless references. Is it > documented anywhere? The dev_data->domain member points to the domain this device is currently attached to, while group points to the iommu-group the device is in. Joerg -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
