Re: [PATCH] PCI: Only restore state that was successfully saved around a reset

[Farhan Ali <alifm@linux.ibm.com>]

Hi Li,

On 11/9/2026 9:33 PM, lirongqing wrote:
> From: Li RongQing <lirongqing@baidu.com>
>
> pci_dev_save_and_disable() returns early when config space is inaccessible,
> without saving anything, but pci_dev_restore() calls pci_restore_state()
> unconditionally and pci_restore_state() does not look at state_saved. After
> the reset makes config space accessible again, the all-zero or stale
> saved_config_space[] array is written back to the device, clearing Command,
> BARs and, for bridges, the bus number registers.
>
> Clear state_saved when the save is skipped and only restore when a state
> was saved.

We should always have a valid state of the device saved at enumeration 
due to commit a2f1e22390ac ("PCI/ERR: Ensure error recoverability at all 
times"). In pci_dev_save_disable(), if the device is inaccessible then 
we want to avoid storing a state that can corrupt the device on restore. 
Since we always have a valid state, we would restore to the last good state.

May I ask what device or driver do you hit this issue?

Thanks

Farhan


>
> Fixes: e18d1abc3bff ("PCI: Avoid saving config space state if inaccessible")
> Signed-off-by: Li RongQing <lirongqing@baidu.com>
> ---
>   drivers/pci/pci.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 67fe565..ddb86dd 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -5156,8 +5156,10 @@ static void pci_dev_save_and_disable(struct pci_dev *dev)
>   	 */
>   	pci_set_power_state(dev, PCI_D0);
>   
> -	if (!pci_dev_config_accessible(dev, "save state"))
> +	if (!pci_dev_config_accessible(dev, "save state")) {
> +		dev->state_saved = false;
>   		return;
> +	}
>   
>   	pci_save_state(dev);
>   	/*
> @@ -5175,7 +5177,8 @@ static void pci_dev_restore(struct pci_dev *dev)
>   	const struct pci_error_handlers *err_handler =
>   			dev->driver ? dev->driver->err_handler : NULL;
>   
> -	pci_restore_state(dev);
> +	if (dev->state_saved)
> +		pci_restore_state(dev);
>   
>   	/*
>   	 * dev->driver->err_handler->reset_done() is protected against