[PATCH 6.6 100/105] PCI/sysfs: Ensure devices are powered for config reads (part 2)

Greg Kroah-Hartman
2025-10-21T19:57:50Z

From: Brian Norris <briannorris@google.com>

Commit 48991e493507 ("PCI/sysfs: Ensure devices are powered for config
reads") was applied to various linux-stable trees. However, prior to
6.12.y, we do not have commit d2bd39c0456b ("PCI: Store all PCIe
Supported Link Speeds"). Therefore, we also need to apply the change to
max_link_speed_show().

This was pointed out here:

Re: Patch "PCI/sysfs: Ensure devices are powered for config reads" has been added to the 6.6-stable tree
https://lore.kernel.org/all/aPEMIreBYZ7yk3cm@google.com/

Original change description follows:

The "max_link_width", "current_link_speed", "current_link_width",
"secondary_bus_number", and "subordinate_bus_number" sysfs files all access
config registers, but they don't check the runtime PM state. If the device
is in D3cold or a parent bridge is suspended, we may see -EINVAL, bogus
values, or worse, depending on implementation details.

Wrap these access in pci_config_pm_runtime_{get,put}() like most of the
rest of the similar sysfs attributes.

Notably, "max_link_speed" does not access config registers; it returns a
cached value since d2bd39c0456b ("PCI: Store all PCIe Supported Link
Speeds").

Fixes: 56c1af4606f0 ("PCI: Add sysfs max_link_speed/width, current_link_speed/width, etc")
Link: https://lore.kernel.org/all/aPEMIreBYZ7yk3cm@google.com/
Signed-off-by: Brian Norris <briannorris@google.com>
Signed-off-by: Brian Norris <briannorris@chromium.org>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/pci/pci-sysfs.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -186,9 +186,15 @@ static ssize_t max_link_speed_show(struc
struct device_attribute *attr, char *buf)
{
struct pci_dev *pdev = to_pci_dev(dev);
+ ssize_t ret;

- return sysfs_emit(buf, "%s\n",
- pci_speed_string(pcie_get_speed_cap(pdev)));
+ /* We read PCI_EXP_LNKCAP, so we need the device to be accessible. */
+ pci_config_pm_runtime_get(pdev);
+ ret = sysfs_emit(buf, "%s\n",
+ pci_speed_string(pcie_get_speed_cap(pdev)));
+ pci_config_pm_runtime_put(pdev);
+
+ return ret;
}
static DEVICE_ATTR_RO(max_link_speed);