Re: [PATCH v7 3/9] PCI: Avoid saving config space state if inaccessible

From: Farhan Ali

Date: Tue Jan 20 2026 - 14:50:56 EST


On 1/19/2026 1:23 PM, Niklas Schnelle wrote:
On Wed, 2026-01-07 at 10:32 -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@xxxxxxxxxxxxx>
---
drivers/pci/pci.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index c105e285cff8..74d21c97654d 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;
const struct pci_error_handlers *err_handler =
dev->driver ? dev->driver->err_handler : NULL;
@@ -4980,6 +4981,12 @@ static void pci_dev_save_and_disable(struct pci_dev *dev)
*/
pci_set_power_state(dev, PCI_D0);
+ pci_read_config_dword(dev, PCI_COMMAND, &val);
Since the PCI_COMMAND field is only 16 bits I think it warrants a
comment that you're reading both PCI_COMMAND and PCI_STATUS and that
both together should never be 0xffffffff and why. I think at least
PCI_STATUS_PARITY should never be set in a config space we want to
restore.

Makes sense will add a comment. Note this is the mechanism used to check device config accessibility in pci_dev_wait() (for some context discussed here https://lore.kernel.org/all/cd1fa387-df80-4756-a2dc-5acdd0f09697@xxxxxxxxxxxxx/).

Thanks

Farhan