PCIe spec 5.0 r1.0 section 2.2.6.2 says that if an Endpoint supports
sending Requests to other Endpoints (as opposed to host memory), the
Endpoint must not send 10-Bit Tag Requests to another given Endpoint
unless an implementation-specific mechanism determines that the Endpoint
supports 10-Bit Tag Completer capability. Add "pci=disable_10bit_tag="
parameter to disable 10-Bit Tag Requester if the peer device does not
support the 10-Bit Tag Completer. This will make P2P traffic safe.

Signed-off-by: Dongdong Liu <redacted>
---
 Documentation/admin-guide/kernel-parameters.txt |  7 ++++
 drivers/pci/pci.c                               | 56 +++++++++++++++++++++++++
 drivers/pci/pci.h                               |  1 +
 drivers/pci/pcie/portdrv_pci.c                  | 13 +++---
 drivers/pci/probe.c                             |  9 ++--
 5 files changed, 78 insertions(+), 8 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index bdb2200..c2c4585 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt

@@ -4019,6 +4019,13 @@
 				bridges without forcing it upstream. Note:
 				this removes isolation between devices and
 				may put more devices in an IOMMU group.
+		disable_10bit_tag=<pci_dev>[; ...]
+				  Specify one or more PCI devices (in the format
+				  specified above) separated by semicolons.
+				  Disable 10-Bit Tag Requester if the peer
+				  device does not support the 10-Bit Tag
+				  Completer.This will make P2P traffic safe.