Re: [PATCH] pci: Add support for unbinding the generic PCI host controller

From: Jan Kiszka
Date: Thu Jun 23 2016 - 13:32:11 EST


On 2016-06-22 08:06, Will Deacon wrote:
> Hi Jan,
>
> On Tue, Jun 21, 2016 at 08:07:50PM +0200, Jan Kiszka wrote:
>> Particularly useful when working in virtual environments where the
>> controller may come and go, but possibly not only there.
>>
>> Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
>> ---
>> drivers/pci/ecam.h | 1 +
>> drivers/pci/host/pci-host-common.c | 13 +++++++++++++
>> drivers/pci/host/pci-host-generic.c | 1 +
>> 3 files changed, 15 insertions(+)
>>
>> diff --git a/drivers/pci/ecam.h b/drivers/pci/ecam.h
>> index 9878beb..5a5f607 100644
>> --- a/drivers/pci/ecam.h
>> +++ b/drivers/pci/ecam.h
>> @@ -63,5 +63,6 @@ extern struct pci_ecam_ops pci_generic_ecam_ops;
>> /* for DT-based PCI controllers that support ECAM */
>> int pci_host_common_probe(struct platform_device *pdev,
>> struct pci_ecam_ops *ops);
>> +int pci_host_common_remove(struct platform_device *pdev);
>> #endif
>> #endif
>> diff --git a/drivers/pci/host/pci-host-common.c b/drivers/pci/host/pci-host-common.c
>> index 8cba7ab..c0ff4b1 100644
>> --- a/drivers/pci/host/pci-host-common.c
>> +++ b/drivers/pci/host/pci-host-common.c
>> @@ -164,6 +164,19 @@ int pci_host_common_probe(struct platform_device *pdev,
>> }
>>
>> pci_bus_add_devices(bus);
>> + platform_set_drvdata(pdev, bus);
>> + return 0;
>> +}
>> +
>> +int pci_host_common_remove(struct platform_device *pdev)
>> +{
>> + struct pci_bus *bus = platform_get_drvdata(pdev);
>> +
>> + pci_lock_rescan_remove();
>> + pci_stop_root_bus(bus);
>> + pci_remove_root_bus(bus);
>> + pci_unlock_rescan_remove();
>
> A couple of comments/questions about this:
>
> - The probe path seems to have some stateful operations outside of PCI
> resources. For example, kzalloc'ing the bus_range resource in
> of_pci_get_host_bridge_resources. Do we need to clean these up
> explicitly?
>
> - Similarly, we don't seem to tear-down the config space mappings and
> data structures for that, so we leak VA space afaict.
>

Good points. But to my understanding, everything is released
automatically on pci_remove_root_bus because all the resources are
registered with the bus which takes care of them during destruction. And
if I trace the release, I find this e.g.

...
devres_release_all() {
_raw_spin_lock_irqsave();
release_nodes() {
_raw_spin_unlock_irqrestore();
devm_action_release() {
gen_pci_unmap_cfg() {

Jan

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