PCI: Enable PASID only if entire path supports End-End TLP prefixes

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-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>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
index 4923a2a..5b78f3b 100644 (file)
--- 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..4c35c29 100644 (file)
--- 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_EE_PREFIX))
+               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 (file)
--- 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..04d7480 100644 (file)
--- 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_EE_PREFIX      0x00200000 /* End-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 */