[PATCH v3 01/10] PCI: Avoid saving error values for config space

Farhan Ali
2025-09-11T18:33:15Z

The current reset process saves the device's config space state before
reset and restores it afterward. However, when a device is in an error
state before reset, config space reads may return error values instead of
valid data. This results in saving corrupted values that get written back
to the device during state restoration.

Avoid saving the state of the config space when the device is in error.
While restoring we only restorei the state that can be restored through
kernel data such as BARs or doesn't depend on the saved state.

Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
---
drivers/pci/pci.c | 29 ++++++++++++++++++++++++++---
drivers/pci/pcie/aer.c | 5 +++++
drivers/pci/pcie/dpc.c | 5 +++++
drivers/pci/pcie/ptm.c | 5 +++++
drivers/pci/tph.c | 5 +++++
drivers/pci/vc.c | 5 +++++
6 files changed, 51 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b0f4d98036cd..4b67d22faf0a 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1720,6 +1720,11 @@ static void pci_restore_pcie_state(struct pci_dev *dev)
struct pci_cap_saved_state *save_state;
u16 *cap;

+ if (!dev->state_saved) {
+ pci_warn(dev, "Not restoring pcie state, no saved state");
+ return;
+ }
+
/*
* Restore max latencies (in the LTR capability) before enabling
* LTR itself in PCI_EXP_DEVCTL2.
@@ -1775,6 +1780,11 @@ static void pci_restore_pcix_state(struct pci_dev *dev)
struct pci_cap_saved_state *save_state;
u16 *cap;

+ if (!dev->state_saved) {
+ pci_warn(dev, "Not restoring pcix state, no saved state");
+ return;
+ }
+
save_state = pci_find_saved_cap(dev, PCI_CAP_ID_PCIX);
pos = pci_find_capability(dev, PCI_CAP_ID_PCIX);
if (!save_state || !pos)
@@ -1792,6 +1802,14 @@ static void pci_restore_pcix_state(struct pci_dev *dev)
int pci_save_state(struct pci_dev *dev)
{
int i;
+ u16 val;
+
+ pci_read_config_word(dev, PCI_DEVICE_ID, &val);
+ if (PCI_POSSIBLE_ERROR(val)) {
+ pci_warn(dev, "Device in error, not saving config space state\n");
+ return -EIO;
+ }
+
/* XXX: 100% dword access ok here? */
for (i = 0; i < 16; i++) {
pci_read_config_dword(dev, i * 4, &dev->saved_config_space[i]);
@@ -1854,6 +1872,14 @@ static void pci_restore_config_space_range(struct pci_dev *pdev,

static void pci_restore_config_space(struct pci_dev *pdev)
{
+ if (!pdev->state_saved) {
+ pci_warn(pdev, "No saved config space, restoring BARs\n");
+ pci_restore_bars(pdev);
+ pci_write_config_word(pdev, PCI_COMMAND,
+ PCI_COMMAND_MEMORY | PCI_COMMAND_IO);
+ return;
+ }
+
if (pdev->hdr_type == PCI_HEADER_TYPE_NORMAL) {
pci_restore_config_space_range(pdev, 10, 15, 0, false);
/* Restore BARs before the command register. */
@@ -1906,9 +1932,6 @@ static void pci_restore_rebar_state(struct pci_dev *pdev)
*/
void pci_restore_state(struct pci_dev *dev)
{
- if (!dev->state_saved)
- return;
-
pci_restore_pcie_state(dev);
pci_restore_pasid_state(dev);
pci_restore_pri_state(dev);
diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
index e286c197d716..dca3502ef669 100644
--- a/drivers/pci/pcie/aer.c
+++ b/drivers/pci/pcie/aer.c
@@ -361,6 +361,11 @@ void pci_restore_aer_state(struct pci_dev *dev)
if (!aer)
return;

+ if (!dev->state_saved) {
+ pci_warn(dev, "Not restoring aer state, no saved state");
+ return;
+ }
+
save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_ERR);
if (!save_state)
return;
diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
index fc18349614d7..62c520af71a7 100644
--- a/drivers/pci/pcie/dpc.c
+++ b/drivers/pci/pcie/dpc.c
@@ -67,6 +67,11 @@ void pci_restore_dpc_state(struct pci_dev *dev)
if (!pci_is_pcie(dev))
return;

+ if (!dev->state_saved) {
+ pci_warn(dev, "Not restoring dpc state, no saved state");
+ return;
+ }
+
save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_DPC);
if (!save_state)
return;
diff --git a/drivers/pci/pcie/ptm.c b/drivers/pci/pcie/ptm.c
index 65e4b008be00..7b5bcc23000d 100644
--- a/drivers/pci/pcie/ptm.c
+++ b/drivers/pci/pcie/ptm.c
@@ -112,6 +112,11 @@ void pci_restore_ptm_state(struct pci_dev *dev)
if (!ptm)
return;

+ if (!dev->state_saved) {
+ pci_warn(dev, "Not restoring ptm state, no saved state");
+ return;
+ }
+
save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_PTM);
if (!save_state)
return;
diff --git a/drivers/pci/tph.c b/drivers/pci/tph.c
index cc64f93709a4..f0f1bae46736 100644
--- a/drivers/pci/tph.c
+++ b/drivers/pci/tph.c
@@ -435,6 +435,11 @@ void pci_restore_tph_state(struct pci_dev *pdev)
if (!pdev->tph_enabled)
return;

+ if (!pdev->state_saved) {
+ pci_warn(pdev, "Not restoring tph state, no saved state");
+ return;
+ }
+
save_state = pci_find_saved_ext_cap(pdev, PCI_EXT_CAP_ID_TPH);
if (!save_state)
return;
diff --git a/drivers/pci/vc.c b/drivers/pci/vc.c
index a4ff7f5f66dd..fda435cd49c1 100644
--- a/drivers/pci/vc.c
+++ b/drivers/pci/vc.c
@@ -391,6 +391,11 @@ void pci_restore_vc_state(struct pci_dev *dev)
{
int i;

+ if (!dev->state_saved) {
+ pci_warn(dev, "Not restoring vc state, no saved state");
+ return;
+ }
+
for (i = 0; i < ARRAY_SIZE(vc_caps); i++) {
int pos;
struct pci_cap_saved_state *save_state;
--
2.43.0