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SubjectRe: [PATCH] vfio/pci: Add extra test for extended capabilities
Date
Alex Williamson <alex.williamson@redhat.com> writes:

> 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.

Just curious, is this part of the spec or just a convention ? I mean
could there be devices with quirks ?

> 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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