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Subject[PATCH V2] PCI: Enable PASID when End-to-End TLP is supported by all bridges
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.

An IOMMU 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 | 9 +++++++++
drivers/pci/probe.c | 17 +++++++++++++++++
include/linux/pci.h | 1 +
include/uapi/linux/pci_regs.h | 1 +
4 files changed, 28 insertions(+)

diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
index 4923a2a..e1b2e6d 100644
--- a/drivers/pci/ats.c
+++ b/drivers/pci/ats.c
@@ -268,6 +268,7 @@ 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;

if (WARN_ON(pdev->pasid_enabled))
@@ -277,6 +278,14 @@ int pci_enable_pasid(struct pci_dev *pdev, int features)
if (!pos)
return -EINVAL;

+ bridge = pci_upstream_bridge(pdev);
+ while (bridge) {
+ if (!bridge->eetlp_prefix)
+ 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/drivers/pci/probe.c b/drivers/pci/probe.c
index ac876e3..a7f7ac1 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2042,6 +2042,22 @@ static void pci_configure_ltr(struct pci_dev *dev)
#endif
}

+static void pci_configure_eetlp_prefix(struct pci_dev *dev)
+{
+#ifdef CONFIG_PCI_PASID
+ u32 cap;
+
+ if (!pci_is_pcie(dev))
+ return;
+
+ pcie_capability_read_dword(dev, PCI_EXP_DEVCAP2, &cap);
+ if (!(cap & PCI_EXP_DEVCAP2_E2ETLP))
+ return;
+
+ dev->eetlp_prefix = 1;
+#endif
+}
+
static void pci_configure_device(struct pci_dev *dev)
{
struct hotplug_params hpp;
@@ -2051,6 +2067,7 @@ static void pci_configure_device(struct pci_dev *dev)
pci_configure_extended_tags(dev, NULL);
pci_configure_relaxed_ordering(dev);
pci_configure_ltr(dev);
+ pci_configure_eetlp_prefix(dev);

memset(&hpp, 0, sizeof(hpp));
ret = pci_get_hp_params(dev, &hpp);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 340029b..cf88d47 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -350,6 +350,7 @@ struct pci_dev {
unsigned int ltr_path:1; /* Latency Tolerance Reporting
supported from root to here */
#endif
+ unsigned int eetlp_prefix:1; /* End-to-End TLP Prefix */

pci_channel_state_t error_state; /* Current connectivity state */
struct device dev; /* Generic device interface */
diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
index 4da87e2..a617ab2 100644
--- a/include/uapi/linux/pci_regs.h
+++ b/include/uapi/linux/pci_regs.h
@@ -636,6 +636,7 @@
#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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