This series adds PCI bus and slot reset interfaces to the already
existing function reset interface. I need this for two reasons, the
first is that not all devices support function level reset. Even
some of those that we detect as supporting a PM reset on D3hot->D0
transition actually don't do any reset. Others have no reset
capability at all. We currently implement a secondary bus reset
escalation from the function reset path, but only when there is a
single devfn on the bus. Drivers like vfio can have ownership of
all of the devices on a bus and should therefore have a path to
initiate a secondary bus reset with multiple devices. This is
particularly required for use of GPUs by userspace, where none of
the predominant GPUs implement a useful function level reset.
The second reason is that even the current function reset escalating
to a secondary bus reset can cause problems with hotplug controllers.
If a root port supports PCIe HP with suprise removal, a bus reset
can trigger a presence detection change, which results in an attempt
to remove the struct device. By having a slot reset interface, we
can involve the hotplug controllers to allow for a controlled bus
reset and avoid this spurious removal attempt.
Takao-san also needs a PCI bus reset interface to quiesce devices
during kexec. I believe this interface also provides that.
Why is this an RFC? I posted this a while back and self-nacked it
because there were issues when hotplug was built as a module. Now
that we're removing module support for PCI hotplug and pciehp in
particular, I think that problem is resolved, but it needs further
testing. Coments welcome. Thanks,
Alex
---
Alex Williamson (7):
pci: Create pci_reset_bridge_secondary_bus()
pci: Add hotplug_slot_ops.reset_slot()
pci: Implement reset_slot for pciehp
pci: Add slot reset option to pci_dev_reset
pci: Split out pci_dev lock/unlock and save/restore
pci: Add slot and bus reset interfaces
pci: Wake-up devices before save for reset
drivers/pci/hotplug/pciehp.h | 1
drivers/pci/hotplug/pciehp_core.c | 12 +
drivers/pci/hotplug/pciehp_hpc.c | 31 ++++
drivers/pci/pci.c | 320 ++++++++++++++++++++++++++++++++++---
include/linux/pci.h | 3
include/linux/pci_hotplug.h | 4
6 files changed, 345 insertions(+), 26 deletions(-)
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