[PATCH v6 04/18] PCI: Reject unreadable ACS controls in isolation checks

[Leon Romanovsky]

From: Leon Romanovsky <leonro@xxxxxxxxxx>

pci_acs_flags_enabled() and the Intel SPT PCH quirk use ACS registers
without checking config-space read errors. A failed read may leave control
state indeterminate yet allow the device to satisfy requested isolation
controls.

Return false when either ACS capability or control state cannot be read.
An unknown state cannot prove isolation.

Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxx>
---
 drivers/pci/pci.c    | 3 ++-
 drivers/pci/quirks.c | 6 ++++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b2879a6be5f8..f7d94ecf9157 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -3594,7 +3594,8 @@ static bool pci_acs_flags_enabled(struct pci_dev *pdev, u16 acs_flags)
 	 */
 	acs_flags &= (pdev->acs_capabilities | PCI_ACS_EC);
 
-	pci_read_config_word(pdev, pos + PCI_ACS_CTRL, &ctrl);
+	if (pci_read_config_word(pdev, pos + PCI_ACS_CTRL, &ctrl))
+		return false;
 	return (ctrl & acs_flags) == acs_flags;
 }
 
diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index de9bbccda21f..d5c3e6802840 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -4992,10 +4992,12 @@ static int pci_quirk_intel_spt_pch_acs(struct pci_dev *dev, u16 acs_flags)
 		return -ENOTTY;
 
 	/* see pci_acs_flags_enabled() */
-	pci_read_config_dword(dev, pos + PCI_ACS_CAP, &cap);
+	if (pci_read_config_dword(dev, pos + PCI_ACS_CAP, &cap))
+		return 0;
 	acs_flags &= (cap | PCI_ACS_EC);
 
-	pci_read_config_dword(dev, pos + INTEL_SPT_ACS_CTRL, &ctrl);
+	if (pci_read_config_dword(dev, pos + INTEL_SPT_ACS_CTRL, &ctrl))
+		return 0;
 
 	return pci_acs_ctrl_enabled(acs_flags, ctrl);
 }

-- 
2.55.0