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Subject[PATCH] vfio/pci: Add extra test for extended capabilities
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If the PCI core set cfg_size isn't large enough for extended
capabilities, then they're not there. Extended config space may be
inaccessible due to a PCI bridge, in which case cfg_size may be cut
short.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
drivers/vfio/pci/vfio_pci_config.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c
index 83cd157..4a62a37 100644
--- a/drivers/vfio/pci/vfio_pci_config.c
+++ b/drivers/vfio/pci/vfio_pci_config.c
@@ -1027,8 +1027,11 @@ static int vfio_cap_len(struct vfio_pci_device *vdev, u8 cap, u8 pos)

if (PCI_X_CMD_VERSION(word)) {
/* Test for extended capabilities */
- pci_read_config_dword(pdev, PCI_CFG_SPACE_SIZE, &dword);
- vdev->extended_caps = (dword != 0);
+ if (pdev->cfg_size > PCI_CFG_SPACE_SIZE) {
+ pci_read_config_dword(pdev, PCI_CFG_SPACE_SIZE,
+ &dword);
+ vdev->extended_caps = (dword != 0);
+ }
return PCI_CAP_PCIX_SIZEOF_V2;
} else
return PCI_CAP_PCIX_SIZEOF_V0;
@@ -1041,8 +1044,10 @@ static int vfio_cap_len(struct vfio_pci_device *vdev, u8 cap, u8 pos)
return byte;
case PCI_CAP_ID_EXP:
/* Test for extended capabilities */
- pci_read_config_dword(pdev, PCI_CFG_SPACE_SIZE, &dword);
- vdev->extended_caps = (dword != 0);
+ if (pdev->cfg_size > PCI_CFG_SPACE_SIZE) {
+ pci_read_config_dword(pdev, PCI_CFG_SPACE_SIZE, &dword);
+ vdev->extended_caps = (dword != 0);
+ }

/* length based on version */
if ((pcie_caps_reg(pdev) & PCI_EXP_FLAGS_VERS) == 1)


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