PCI: Add support for PASID capability

Devices supporting Process Address Space Identifiers
(PASIDs) can use an IOMMU to access multiple IO address
spaces at the same time. A PCIe device indicates support for
this feature by implementing the PASID capability. This
patch adds support for the capability to the Linux kernel.

Reviewed-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

2 files changed, 126 insertions, 0 deletions

diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
index fb1e9707f91e..cec66064ee4b 100644
--- a/drivers/pci/Kconfig
+++ b/drivers/pci/Kconfig
@@ -94,6 +94,19 @@ config PCI_PRI
 
           If unsure, say N.
 
+config PCI_PASID
+        bool "PCI PASID support"
+        depends on PCI
+        select PCI_ATS
+        help
+          Process Address Space Identifiers (PASIDs) can be used by PCI devices
+          to access more than one IO address space at the same time. To make
+          use of this feature an IOMMU is required which also supports PASIDs.
+          Select this option if you have such an IOMMU and want to compile the
+          driver for it into your kernel.
+
+          If unsure, say N.
+
 config PCI_IOAPIC
         bool
         depends on PCI
diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
index bf892a025d4f..f727a09eb72f 100644
--- a/drivers/pci/ats.c
+++ b/drivers/pci/ats.c
@@ -7,6 +7,7 @@
  * PCI Express I/O Virtualization (IOV) support.
  *   Address Translation Service 1.0
  *   Page Request Interface added by Joerg Roedel <joerg.roedel@amd.com>
+ *   PASID support added by Joerg Roedel <joerg.roedel@amd.com>
  */
 
 #include <linux/pci-ats.h>
@@ -323,3 +324,115 @@ int pci_pri_status(struct pci_dev *pdev)
 }
 EXPORT_SYMBOL_GPL(pci_pri_status);
 #endif /* CONFIG_PCI_PRI */
+
+#ifdef CONFIG_PCI_PASID
+/**
+ * pci_enable_pasid - Enable the PASID capability
+ * @pdev: PCI device structure
+ * @features: Features to enable
+ *
+ * Returns 0 on success, negative value on error. This function checks
+ * whether the features are actually supported by the device and returns
+ * an error if not.
+ */
+int pci_enable_pasid(struct pci_dev *pdev, int features)
+{
+        u16 control, supported;
+        int pos;
+
+        pos = pci_find_ext_capability(pdev, PCI_PASID_CAP);
+        if (!pos)
+                return -EINVAL;
+
+        pci_read_config_word(pdev, pos + PCI_PASID_CONTROL_OFF, &control);
+        pci_read_config_word(pdev, pos + PCI_PASID_CAP_OFF,     &supported);
+
+        if (!(supported & PCI_PASID_ENABLE))
+                return -EINVAL;
+
+        supported &= PCI_PASID_EXEC | PCI_PASID_PRIV;
+
+        /* User wants to enable anything unsupported? */
+        if ((supported & features) != features)
+                return -EINVAL;
+
+        control = PCI_PASID_ENABLE | features;
+
+        pci_write_config_word(pdev, pos + PCI_PASID_CONTROL_OFF, control);
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(pci_enable_pasid);
+
+/**
+ * pci_disable_pasid - Disable the PASID capability
+ * @pdev: PCI device structure
+ *
+ */
+void pci_disable_pasid(struct pci_dev *pdev)
+{
+        u16 control = 0;
+        int pos;
+
+        pos = pci_find_ext_capability(pdev, PCI_PASID_CAP);
+        if (!pos)
+                return;
+
+        pci_write_config_word(pdev, pos + PCI_PASID_CONTROL_OFF, control);
+}
+EXPORT_SYMBOL_GPL(pci_disable_pasid);
+
+/**
+ * pci_pasid_features - Check which PASID features are supported
+ * @pdev: PCI device structure
+ *
+ * Returns a negative value when no PASI capability is present.
+ * Otherwise is returns a bitmask with supported features. Current
+ * features reported are:
+ * PCI_PASID_ENABLE - PASID capability can be enabled
+ * PCI_PASID_EXEC - Execute permission supported
+ * PCI_PASID_PRIV - Priviledged mode supported
+ */
+int pci_pasid_features(struct pci_dev *pdev)
+{
+        u16 supported;
+        int pos;
+
+        pos = pci_find_ext_capability(pdev, PCI_PASID_CAP);
+        if (!pos)
+                return -EINVAL;
+
+        pci_read_config_word(pdev, pos + PCI_PASID_CAP_OFF, &supported);
+
+        supported &= PCI_PASID_ENABLE | PCI_PASID_EXEC | PCI_PASID_PRIV;
+
+        return supported;
+}
+EXPORT_SYMBOL_GPL(pci_pasid_features);
+
+#define PASID_NUMBER_SHIFT      8
+#define PASID_NUMBER_MASK       (0x1f << PASID_NUMBER_SHIFT)
+/**
+ * pci_max_pasid - Get maximum number of PASIDs supported by device
+ * @pdev: PCI device structure
+ *
+ * Returns negative value when PASID capability is not present.
+ * Otherwise it returns the numer of supported PASIDs.
+ */
+int pci_max_pasids(struct pci_dev *pdev)
+{
+        u16 supported;
+        int pos;
+
+        pos = pci_find_ext_capability(pdev, PCI_PASID_CAP);
+        if (!pos)
+                return -EINVAL;
+
+        pci_read_config_word(pdev, pos + PCI_PASID_CAP_OFF, &supported);
+
+        supported = (supported & PASID_NUMBER_MASK) >> PASID_NUMBER_SHIFT;
+
+        return (1 << supported);
+}
+EXPORT_SYMBOL_GPL(pci_max_pasids);
+#endif /* CONFIG_PCI_PASID */