linux-kernel - [PATCH] Revert "PCI: Avoid reset when disabled via sysfs"

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Message-ID: <20250414211828.3530741-1-alex.williamson@redhat.com>
Date: Mon, 14 Apr 2025 15:18:23 -0600
From: Alex Williamson <alex.williamson@...hat.com>
To: helgaas@...nel.org
Cc: Alex Williamson <alex.williamson@...hat.com>,
	naravamudan@...dia.com,
	bhelgaas@...gle.com,
	raphael.norwitz@...anix.com,
	ameynarkhede03@...il.com,
	linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	jgg@...dia.com,
	yishaih@...dia.com,
	shameerali.kolothum.thodi@...wei.com,
	kevin.tian@...el.com,
	kvm@...r.kernel.org,
	cp@...olutedigital.net,
	stable@...r.kernel.org
Subject: [PATCH] Revert "PCI: Avoid reset when disabled via sysfs"

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@...olutedigital.net>
Link: https://lore.kernel.org/all/808e1111-27b7-f35b-6d5c-5b275e73677b@absolutedigital.net
Cc: stable@...r.kernel.org
Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
---
 drivers/pci/pci.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 4d7c9f64ea24..e77d5b53c0ce 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -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;
-- 
2.48.1