6.6-stable review patch. If anyone has any objections, please let me know.
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From: Alex Williamson alex.williamson@redhat.com
commit bc0b828ef6e561081ebc4c758d0c4d166bb9829c upstream.
This reverts commit 479380efe1625e251008d24b2810283db60d6fcd.
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: 479380efe162 ("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@absolutedig... 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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/pci/pci.c | 4 ---- 1 file changed, 4 deletions(-)
--- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -5714,8 +5714,6 @@ static bool pci_bus_resettable(struct pc 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; @@ -5792,8 +5790,6 @@ static bool pci_slot_resettable(struct p 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;