[PATCH v5 3/9] PCI: Avoid saving error values for config space

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

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 restore 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      | 25 ++++++++++++++++++++++---
 drivers/pci/pcie/aer.c |  3 +++
 drivers/pci/pcie/dpc.c |  3 +++
 drivers/pci/pcie/ptm.c |  3 +++
 drivers/pci/tph.c      |  3 +++
 drivers/pci/vc.c       |  3 +++
 6 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 36ee38e0d817..3a9a283b5be9 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1669,6 +1669,9 @@ static void pci_restore_pcie_state(struct pci_dev *dev)
 	struct pci_cap_saved_state *save_state;
 	u16 *cap;
 
+	if (!dev->state_saved)
+		return;
+
 	/*
 	 * Restore max latencies (in the LTR capability) before enabling
 	 * LTR itself in PCI_EXP_DEVCTL2.
@@ -1724,6 +1727,9 @@ static void pci_restore_pcix_state(struct pci_dev *dev)
 	struct pci_cap_saved_state *save_state;
 	u16 *cap;
 
+	if (!dev->state_saved)
+		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)
@@ -1741,6 +1747,14 @@ static void pci_restore_pcix_state(struct pci_dev *dev)
 int pci_save_state(struct pci_dev *dev)
 {
 	int i;
+	u32 val;
+
+	pci_read_config_dword(dev, PCI_COMMAND, &val);
+	if (PCI_POSSIBLE_ERROR(val)) {
+		pci_warn(dev, "Device config space inaccessible, will only be partially restored\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]);
@@ -1803,6 +1817,14 @@ 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. */
@@ -1855,9 +1877,6 @@ 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 0b5ed4722ac3..9a898089f984 100644
--- a/drivers/pci/pcie/aer.c
+++ b/drivers/pci/pcie/aer.c
@@ -371,6 +371,9 @@ void pci_restore_aer_state(struct pci_dev *dev)
 	if (!aer)
 		return;
 
+	if (!dev->state_saved)
+		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..e0d7034c2cd8 100644
--- a/drivers/pci/pcie/dpc.c
+++ b/drivers/pci/pcie/dpc.c
@@ -67,6 +67,9 @@ void pci_restore_dpc_state(struct pci_dev *dev)
 	if (!pci_is_pcie(dev))
 		return;
 
+	if (!dev->state_saved)
+		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..78613000acfb 100644
--- a/drivers/pci/pcie/ptm.c
+++ b/drivers/pci/pcie/ptm.c
@@ -112,6 +112,9 @@ void pci_restore_ptm_state(struct pci_dev *dev)
 	if (!ptm)
 		return;
 
+	if (!dev->state_saved)
+		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..c0fa1b9a7a78 100644
--- a/drivers/pci/tph.c
+++ b/drivers/pci/tph.c
@@ -435,6 +435,9 @@ void pci_restore_tph_state(struct pci_dev *pdev)
 	if (!pdev->tph_enabled)
 		return;
 
+	if (!pdev->state_saved)
+		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..00609c7e032a 100644
--- a/drivers/pci/vc.c
+++ b/drivers/pci/vc.c
@@ -391,6 +391,9 @@ void pci_restore_vc_state(struct pci_dev *dev)
 {
 	int i;
 
+	if (!dev->state_saved)
+		return;
+
 	for (i = 0; i < ARRAY_SIZE(vc_caps); i++) {
 		int pos;
 		struct pci_cap_saved_state *save_state;
-- 
2.43.0