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Subject[PATCH] PCI: Do not enable PASID when End-to-End TLP is not supported
Date
A PCIe endpoint carries the process address space identifier (PASID) in
the TLP prefix as part of the memory read/write transaction. The address
information in the TLP is relevant only for a given PASID context.

A translation agent takes PASID value and the address information from the
TLP to look up the physical address in the system.

If a bridge drops the TLP prefix, the translation agent can resolve the
address to an incorrect location and cause data corruption. Prevent
this condition by requiring End-to-End TLP prefix to be supported on the
entire data path between the endpoint and the root port.

Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
---
drivers/pci/ats.c | 16 ++++++++++++++++
include/uapi/linux/pci_regs.h | 1 +
2 files changed, 17 insertions(+)

diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
index 89305b5..0bcded5 100644
--- a/drivers/pci/ats.c
+++ b/drivers/pci/ats.c
@@ -265,7 +265,9 @@ EXPORT_SYMBOL_GPL(pci_reset_pri);
int pci_enable_pasid(struct pci_dev *pdev, int features)
{
u16 control, supported;
+ struct pci_dev *bridge;
int pos;
+ u32 cap;

if (WARN_ON(pdev->pasid_enabled))
return -EBUSY;
@@ -274,6 +276,20 @@ int pci_enable_pasid(struct pci_dev *pdev, int features)
if (!pos)
return -EINVAL;

+ bridge = pci_upstream_bridge(pdev);
+ while (bridge) {
+ if (!pci_find_capability(bridge, PCI_CAP_ID_EXP))
+ return -EINVAL;
+
+ if (pcie_capability_read_dword(bridge, PCI_EXP_DEVCAP2, &cap))
+ return -EINVAL;
+
+ if (!(cap & PCI_EXP_DEVCAP2_E2ETLP))
+ return -EINVAL;
+
+ bridge = pci_upstream_bridge(bridge);
+ }
+
pci_read_config_word(pdev, pos + PCI_PASID_CAP, &supported);
supported &= PCI_PASID_CAP_EXEC | PCI_PASID_CAP_PRIV;

diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
index 103ba79..d91dea5 100644
--- a/include/uapi/linux/pci_regs.h
+++ b/include/uapi/linux/pci_regs.h
@@ -634,6 +634,7 @@
#define PCI_EXP_DEVCAP2_OBFF_MASK 0x000c0000 /* OBFF support mechanism */
#define PCI_EXP_DEVCAP2_OBFF_MSG 0x00040000 /* New message signaling */
#define PCI_EXP_DEVCAP2_OBFF_WAKE 0x00080000 /* Re-use WAKE# for OBFF */
+#define PCI_EXP_DEVCAP2_E2ETLP 0x00200000 /* End-to-End TLP Prefix */
#define PCI_EXP_DEVCTL2 40 /* Device Control 2 */
#define PCI_EXP_DEVCTL2_COMP_TIMEOUT 0x000f /* Completion Timeout Value */
#define PCI_EXP_DEVCTL2_COMP_TMOUT_DIS 0x0010 /* Completion Timeout Disable */
--
2.7.4
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