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Subject[PATCH V3] 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.

PASID is an End-End TLP Prefix (PCIe r4.0, sec 6.20). Sec 2.2.10.2 says

It is an error to receive a TLP with an End-End TLP Prefix by a
Receiver that does not support End-End TLP Prefixes. A TLP in
violation of this rule is handled as a Malformed TLP. This is a
reported error associated with the Receiving Port (see Section 6.2).

Prevent error condition by proactively requiring End-to-End TLP
prefix to be supported on the entire data path between the endpoint and
the root port before enabling PASID.

Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
---
drivers/pci/ats.c | 3 +++
drivers/pci/probe.c | 24 ++++++++++++++++++++++++
include/linux/pci.h | 1 +
include/uapi/linux/pci_regs.h | 1 +
4 files changed, 29 insertions(+)

diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
index 4923a2a..5b78f3b 100644
--- a/drivers/pci/ats.c
+++ b/drivers/pci/ats.c
@@ -273,6 +273,9 @@ int pci_enable_pasid(struct pci_dev *pdev, int features)
if (WARN_ON(pdev->pasid_enabled))
return -EBUSY;

+ if (!pdev->eetlp_prefix_path)
+ return -EINVAL;
+
pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PASID);
if (!pos)
return -EINVAL;
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index ac876e3..39fd3ac 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2042,6 +2042,29 @@ static void pci_configure_ltr(struct pci_dev *dev)
#endif
}

+static void pci_configure_eetlp_prefix(struct pci_dev *dev)
+{
+#ifdef CONFIG_PCI_PASID
+ struct pci_dev *bridge;
+ u32 cap;
+
+ if (!pci_is_pcie(dev))
+ return;
+
+ pcie_capability_read_dword(dev, PCI_EXP_DEVCAP2, &cap);
+ if (!(cap & PCI_EXP_DEVCAP2_E2ETLP))
+ return;
+
+ if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT)
+ dev->eetlp_prefix_path = 1;
+ else {
+ bridge = pci_upstream_bridge(dev);
+ if (bridge && bridge->eetlp_prefix_path)
+ dev->eetlp_prefix_path = 1;
+ }
+#endif
+}
+
static void pci_configure_device(struct pci_dev *dev)
{
struct hotplug_params hpp;
@@ -2051,6 +2074,7 @@ 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..6ba8184 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_path: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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