2014-06-12 16:44:19

by Alex Williamson

Subject: [PATCH] vfio/pci: Add extra test for extended capabilities

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 <[email protected]>
---
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)

2014-06-12 20:12:11

by Bandan Das

Subject: Re: [PATCH] vfio/pci: Add extra test for extended capabilities

Alex Williamson <[email protected]> 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 <[email protected]>
> ---
> 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)
>
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html

2014-06-12 20:29:06

by Alex Williamson

Subject: Re: [PATCH] vfio/pci: Add extra test for extended capabilities

On Thu, 2014-06-12 at 16:12 -0400, Bandan Das wrote:
> Alex Williamson <[email protected]> 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 ?

The PCIe bridge spec indicates that PCIe-to-PCI bridges should handle
extended config accesses as an unsupported request. But as in 78916b00,
we've seen that's not always the case. This just makes us trust
PCI-core before the capabilities we find on the device. The current
quirk in the referenced commit is for a relatively uncommon topology,
but never rule out that we couldn't have a device quirked to avoid
touching extended config space too. Thanks,

Alex

> > Signed-off-by: Alex Williamson <[email protected]>
> > ---
> > 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)
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe kvm" in
> > the body of a message to [email protected]
> > More majordomo info at http://vger.kernel.org/majordomo-info.html

2014-06-12 20:40:33

by Bandan Das

Subject: Re: [PATCH] vfio/pci: Add extra test for extended capabilities

Alex Williamson <[email protected]> writes:

> On Thu, 2014-06-12 at 16:12 -0400, Bandan Das wrote:
>> Alex Williamson <[email protected]> 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 ?
>
> The PCIe bridge spec indicates that PCIe-to-PCI bridges should handle
> extended config accesses as an unsupported request. But as in 78916b00,
> we've seen that's not always the case. This just makes us trust
> PCI-core before the capabilities we find on the device. The current
> quirk in the referenced commit is for a relatively uncommon topology,
> but never rule out that we couldn't have a device quirked to avoid
> touching extended config space too. Thanks,

Ok, Understood, Thanks!

> Alex
>
>> > Signed-off-by: Alex Williamson <[email protected]>
>> > ---
>> > 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)
>> >
>> > --
>> > To unsubscribe from this list: send the line "unsubscribe kvm" in
>> > the body of a message to [email protected]
>> > More majordomo info at http://vger.kernel.org/majordomo-info.html