Re: [PATCH v8 3/9] PCI: Avoid saving config space state if inaccessible

Niklas Schnelle
2026-01-26T21:01:21Z

On Thu, 2026-01-22 at 11:44 -0800, Farhan Ali wrote:
> The current reset process saves the device's config space state before
> reset and restores it afterward. However errors may occur unexpectedly and
> it may then be impossible to save config space because the device may be
> inaccessible (e.g. DPC) or config space may be corrupted. This results in
> saving corrupted values that get written back to the device during state
> restoration.
>
> With a reset we want to recover/restore the device into a functional state.
> So avoid saving the state of the config space when the device config space
> is inaccessible.
>
> Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
> ---
> drivers/pci/pci.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index c105e285cff8..e7beaf1f65a7 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -4960,6 +4960,7 @@ EXPORT_SYMBOL_GPL(pci_dev_unlock);
>
> static void pci_dev_save_and_disable(struct pci_dev *dev)
> {
> + u32 val;

Nit: I believe the PCI subsystem prefers reverse X-mas tree
declarations

> const struct pci_error_handlers *err_handler =
> dev->driver ? dev->driver->err_handler : NULL;
>
> @@ -4980,6 +4981,19 @@ static void pci_dev_save_and_disable(struct pci_dev *dev)
> */
> pci_set_power_state(dev, PCI_D0);
>
> + /*
> + * If device's config space is inaccessible it can return ~0 for
> + * any reads. Since VFs can also return ~0 for Device and Vendor ID
> + * check Command and Status registers. At the very least we should
> + * avoid restoring config space for device with error bits set in
> + * Status register.
> + */
> + pci_read_config_dword(dev, PCI_COMMAND, &val);
> + if (PCI_POSSIBLE_ERROR(val)) {
> + pci_warn(dev, "Device config space inaccessible\n");
> + return;
> + }
> +
> pci_save_state(dev);
> /*
> * Disable the device by clearing the Command register, except for

Looks good to me thanks! Feel free to add:

Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>