Commit bc0b828e authored Apr 14, 2025 by Alex Williamson Committed by Bjorn Helgaas Apr 15, 2025

Revert "PCI: Avoid reset when disabled via sysfs"

This reverts commit 479380ef.

The reset_method attribute on a PCI device is only intended to manage the
availability of function scoped resets for a device. It was never intended
to restrict resets targeting the bus or slot.

In introducing a restriction that each device must support function level
reset by testing pci_reset_supported(), we essentially create a catch-22,
that a device must have a function scope reset in order to support bus/slot
reset, when we use bus/slot reset to effect a reset of a device that does
not support a function scoped reset, especially multi-function devices.

This breaks the majority of uses cases where vfio-pci uses bus/slot resets
to manage multifunction devices that do not support function scoped resets.

Fixes: 479380ef ("PCI: Avoid reset when disabled via sysfs")
Reported-by: Cal Peake <cp@absolutedigital.net>
Closes: https://lore.kernel.org/all/808e1111-27b7-f35b-6d5c-5b275e73677b@absolutedigital.net

Reported-by: Athul Krishna <athul.krishna.kr@protonmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220010

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20250414211828.3530741-1-alex.williamson@redhat.com

parent 0af2f6be

drivers/pci/pci.c

+0 −4

Original line number	Diff line number	Diff line
		@@ -5429,8 +5429,6 @@ static bool pci_bus_resettable(struct pci_bus *bus)
		return false;

		list_for_each_entry(dev, &bus->devices, bus_list) {
		if (!pci_reset_supported(dev))
		return false;
		if (dev->dev_flags & PCI_DEV_FLAGS_NO_BUS_RESET \|\|
		(dev->subordinate && !pci_bus_resettable(dev->subordinate)))
		return false;
		@@ -5507,8 +5505,6 @@ static bool pci_slot_resettable(struct pci_slot *slot)
		list_for_each_entry(dev, &slot->bus->devices, bus_list) {
		if (!dev->slot \|\| dev->slot != slot)
		continue;
		if (!pci_reset_supported(dev))
		return false;
		if (dev->dev_flags & PCI_DEV_FLAGS_NO_BUS_RESET \|\|
		(dev->subordinate && !pci_bus_resettable(dev->subordinate)))
		return false;