On 14/7/18 9:31 am, Logan Gunthorpe wrote:

Changes since v5:
* Add a quirk to handle the Intel SPT PCH case (as pointed out by Alex)
* Warn in the case that we try to disable ACS redirect on a device
  that doesn't have the ACS capability (also suggested by Alex)
* Collect reviewed-by tag from Alex
* Rebased onto v4.18-rc4 (no conflicts)

Changes since v4:
* Fixed a couple documentation mistakes spotted by Randy

Changes since v3:
* Removed some of the cruft that was copied from the resource_alignment
  paramater (per Alex)
* A number of docuemntation fixes as noticed by Alex and Willy

Changes since v2:
* Rebased onto v4.18-rc1 (no conflicts)
* Minor tweaks to the documentation per Andy
* Removed the "path:" prefix and use the path parsing code
  for simple devices (as it works the same). Per a suggestion from Alex

Changes since v1:
* Reworked pci_dev_str_match_path using strrchr as suggested by Alex
* Collected Christian's Acks

--

Hi,

As discussed in our PCI P2PDMA series, we'd like to add a kernel
parameter for selectively disabling ACS redirection for select
bridges. Seeing this turned out to be a small series in itself, we've
decided to send this separately from the P2P work.

This series generalizes the code already done for the resource_alignment
option that already exists. The first patch creates a helper function
to match PCI devices against strings based on the code that already
existed in pci_specified_resource_alignment().

The second patch expands the new helper to optionally take a path of
PCI devfns. This is to address Alex's renumbering concern when using
simple bus-devfns. The implementation is essentially how he described it and
similar to the Intel VT-d spec (Section 8.3.1).

The final patch adds the disable_acs_redir kernel parameter which takes
a list of PCI devices and will disable the ACS P2P Request Redirect,
ACS P2P Completion Redirect and ACS P2P Egress Control bits for the
selected devices. This allows P2P traffic between selected bridges and
seeing it's done at boot, before the IOMMU groups will be created, the
groups will match the security provided by ACS.

I am pretty sure it's been discussed but just to make sure I understand the
whole picture - why exactly does ACS have to be disabled at the boot time?
We could enable it, for example, for 2 devices in the same VFIO container
if there are in isolatable part of the PCI tree, or we just do not want to
make VFIO containers or QEMU aware of PCI hierarchy (I can see why, just
double checking)? Thanks.

Thanks,

Logan

--

Logan Gunthorpe (4):
  PCI: Make specifying PCI devices in kernel parameters reusable
  PCI: Allow specifying devices using a base bus and path of devfns
  PCI: Introduce disable_acs_redir quirk
  PCI: Introduce the disable_acs_redir parameter

 Documentation/admin-guide/kernel-parameters.txt |  41 +++-
 drivers/pci/pci.c                               | 310 +++++++++++++++++++-----
 drivers/pci/quirks.c                            |  78 +++++-
 include/linux/pci.h                             |   5 +
 4 files changed, 361 insertions(+), 73 deletions(-)

--
2.11.0

-- 
Alexey
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