[PATCH v4 4/7] iommu/arm: Introduce iommu_add_dt_pci_sideband_ids API

[Stewart Hildebrand <stewart.hildebrand@xxxxxxx>]

From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>

The main purpose of this patch is to add a way to register PCI device
(which is behind the IOMMU) using the generic PCI-IOMMU DT bindings [1]
before assigning that device to a domain.

This behaves similarly to the existing iommu_add_dt_device API, except it
handles PCI devices, and it is to be invoked from the add_device hook in the
SMMU driver.

The function of_map_id to translate an ID through a downstream mapping
(which is also suitable for mapping Requester ID) was borrowed from Linux
(v5.10-rc6) and updated according to the Xen code base.

[1] 
https://www.kernel.org/doc/Documentation/devicetree/bindings/pci/pci-iommu.txt

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
---
v3->v4:
* wrap #include <asm/acpi.h> and if ( acpi_disabled ) in #ifdef CONFIG_ACPI
* fix Michal's remarks about style, parenthesis, and print formats
* remove !ops->dt_xlate check since it is already in iommu_dt_xlate helper
* rename s/iommu_dt_pci_map_id/dt_map_id/ because it is generic, not specific
  to iommu
* update commit description

v2->v3:
* new patch title (was: iommu/arm: Introduce iommu_add_dt_pci_device API)
* renamed function
  from: iommu_add_dt_pci_device
  to: iommu_add_dt_pci_sideband_ids
* removed stale ops->add_device check
* iommu.h: add empty stub iommu_add_dt_pci_sideband_ids for !HAS_DEVICE_TREE
* iommu.h: add iommu_add_pci_sideband_ids helper
* iommu.h: don't wrap prototype in #ifdef CONFIG_HAS_PCI
* s/iommu_fwspec_free(pci_to_dev(pdev))/iommu_fwspec_free(dev)/

v1->v2:
* remove extra devfn parameter since pdev fully describes the device
* remove ops->add_device() call from iommu_add_dt_pci_device(). Instead, rely on
  the existing iommu call in iommu_add_device().
* move the ops->add_device and ops->dt_xlate checks earlier

downstream->v1:
* rebase
* add const qualifier to struct dt_device_node *np arg in dt_map_id()
* add const qualifier to struct dt_device_node *np declaration in 
iommu_add_pci_device()
* use stdint.h types instead of u8/u32/etc...
* rename functions:
  s/dt_iommu_xlate/iommu_dt_xlate/
  s/dt_map_id/iommu_dt_pci_map_id/
  s/iommu_add_pci_device/iommu_add_dt_pci_device/
* add device_is_protected check in iommu_add_dt_pci_device
* wrap prototypes in CONFIG_HAS_PCI

(cherry picked from commit 734e3bf6ee77e7947667ab8fa96c25b349c2e1da from
 the downstream branch poc/pci-passthrough from
 https://gitlab.com/xen-project/people/bmarquis/xen-arm-poc.git)
---
 xen/drivers/passthrough/device_tree.c | 134 ++++++++++++++++++++++++++
 xen/include/xen/device_tree.h         |  25 +++++
 xen/include/xen/iommu.h               |  22 ++++-
 3 files changed, 180 insertions(+), 1 deletion(-)

diff --git a/xen/drivers/passthrough/device_tree.c 
b/xen/drivers/passthrough/device_tree.c
index ff9e66ebf92a..bd0aed5df651 100644
--- a/xen/drivers/passthrough/device_tree.c
+++ b/xen/drivers/passthrough/device_tree.c
@@ -154,6 +154,140 @@ static int iommu_dt_xlate(struct device *dev,
     return ops->dt_xlate(dev, iommu_spec);
 }
 
+#ifdef CONFIG_HAS_PCI
+int dt_map_id(const struct dt_device_node *np, uint32_t id,
+              const char *map_name, const char *map_mask_name,
+              struct dt_device_node **target, uint32_t *id_out)
+{
+    uint32_t map_mask, masked_id, map_len;
+    const __be32 *map = NULL;
+
+    if ( !np || !map_name || (!target && !id_out) )
+        return -EINVAL;
+
+    map = dt_get_property(np, map_name, &map_len);
+    if ( !map )
+    {
+        if ( target )
+            return -ENODEV;
+
+        /* Otherwise, no map implies no translation */
+        *id_out = id;
+        return 0;
+    }
+
+    if ( !map_len || (map_len % (4 * sizeof(*map))) )
+    {
+        printk(XENLOG_ERR "%s: Error: Bad %s length: %u\n", np->full_name,
+               map_name, map_len);
+        return -EINVAL;
+    }
+
+    /* The default is to select all bits. */
+    map_mask = 0xffffffff;
+
+    /*
+     * Can be overridden by "{iommu,msi}-map-mask" property.
+     * If df_property_read_u32() fails, the default is used.
+     */
+    if ( map_mask_name )
+        dt_property_read_u32(np, map_mask_name, &map_mask);
+
+    masked_id = map_mask & id;
+    for ( ; (int)map_len > 0; map_len -= 4 * sizeof(*map), map += 4 )
+    {
+        struct dt_device_node *phandle_node;
+        uint32_t id_base = be32_to_cpup(map + 0);
+        uint32_t phandle = be32_to_cpup(map + 1);
+        uint32_t out_base = be32_to_cpup(map + 2);
+        uint32_t id_len = be32_to_cpup(map + 3);
+
+        if ( id_base & ~map_mask )
+        {
+            printk(XENLOG_ERR "%s: Invalid %s translation - %s-mask 
(0x%"PRIx32") ignores id-base (0x%"PRIx32")\n",
+                   np->full_name, map_name, map_name, map_mask, id_base);
+            return -EFAULT;
+        }
+
+        if ( (masked_id < id_base) || (masked_id >= (id_base + id_len)) )
+            continue;
+
+        phandle_node = dt_find_node_by_phandle(phandle);
+        if ( !phandle_node )
+            return -ENODEV;
+
+        if ( target )
+        {
+            if ( !*target )
+                *target = phandle_node;
+
+            if ( *target != phandle_node )
+                continue;
+        }
+
+        if ( id_out )
+            *id_out = masked_id - id_base + out_base;
+
+        printk(XENLOG_DEBUG "%s: %s, using mask %08"PRIx32", id-base: 
%08"PRIx32", out-base: %08"PRIx32", length: %08"PRIx32", id: %08"PRIx32" -> 
%08"PRIx32"\n",
+               np->full_name, map_name, map_mask, id_base, out_base, id_len, 
id,
+               masked_id - id_base + out_base);
+        return 0;
+    }
+
+    printk(XENLOG_ERR "%s: no %s translation for id 0x%"PRIx32" on %s\n",
+           np->full_name, map_name, id, (target && *target) ? 
(*target)->full_name : NULL);
+
+    /*
+     * NOTE: Linux bypasses translation without returning an error here,
+     * but should we behave in the same way on Xen? Restrict for now.
+     */
+    return -EFAULT;
+}
+
+int iommu_add_dt_pci_sideband_ids(struct pci_dev *pdev)
+{
+    const struct iommu_ops *ops = iommu_get_ops();
+    struct dt_phandle_args iommu_spec = { .args_count = 1 };
+    struct device *dev = pci_to_dev(pdev);
+    const struct dt_device_node *np;
+    int rc = NO_IOMMU;
+
+    if ( !iommu_enabled )
+        return NO_IOMMU;
+
+    if ( !ops )
+        return -EINVAL;
+
+    if ( device_is_protected(dev) )
+        return 0;
+
+    if ( dev_iommu_fwspec_get(dev) )
+        return -EEXIST;
+
+    np = pci_find_host_bridge_node(pdev);
+    if ( !np )
+        return -ENODEV;
+
+    /*
+     * According to the Documentation/devicetree/bindings/pci/pci-iommu.txt
+     * from Linux.
+     */
+    rc = dt_map_id(np, PCI_BDF(pdev->bus, pdev->devfn), "iommu-map",
+                   "iommu-map-mask", &iommu_spec.np, iommu_spec.args);
+    if ( rc )
+        return (rc == -ENODEV) ? NO_IOMMU : rc;
+
+    rc = iommu_dt_xlate(dev, &iommu_spec);
+    if ( rc < 0 )
+    {
+        iommu_fwspec_free(dev);
+        return -EINVAL;
+    }
+
+    return rc;
+}
+#endif /* CONFIG_HAS_PCI */
+
 int iommu_add_dt_device(struct dt_device_node *np)
 {
     const struct iommu_ops *ops = iommu_get_ops();
diff --git a/xen/include/xen/device_tree.h b/xen/include/xen/device_tree.h
index c2f315140560..8385cd538a58 100644
--- a/xen/include/xen/device_tree.h
+++ b/xen/include/xen/device_tree.h
@@ -892,6 +892,31 @@ int dt_count_phandle_with_args(const struct dt_device_node 
*np,
  */
 int dt_get_pci_domain_nr(struct dt_device_node *node);
 
+#ifdef CONFIG_HAS_PCI
+/**
+ * dt_map_id - Translate an ID through a downstream mapping.
+ * @np: root complex device node.
+ * @id: device ID to map.
+ * @map_name: property name of the map to use.
+ * @map_mask_name: optional property name of the mask to use.
+ * @target: optional pointer to a target device node.
+ * @id_out: optional pointer to receive the translated ID.
+ *
+ * Given a device ID, look up the appropriate implementation-defined
+ * platform ID and/or the target device which receives transactions on that
+ * ID, as per the "iommu-map" and "msi-map" bindings. Either of @target or
+ * @id_out may be NULL if only the other is required. If @target points to
+ * a non-NULL device node pointer, only entries targeting that node will be
+ * matched; if it points to a NULL value, it will receive the device node of
+ * the first matching target phandle, with a reference held.
+ *
+ * Return: 0 on success or a standard error code on failure.
+ */
+int dt_map_id(const struct dt_device_node *np, uint32_t id,
+              const char *map_name, const char *map_mask_name,
+              struct dt_device_node **target, uint32_t *id_out);
+#endif /* CONFIG_HAS_PCI */
+
 struct dt_device_node *dt_find_node_by_phandle(dt_phandle handle);
 
 #ifdef CONFIG_DEVICE_TREE_DEBUG
diff --git a/xen/include/xen/iommu.h b/xen/include/xen/iommu.h
index 405db59971c5..3cac177840f7 100644
--- a/xen/include/xen/iommu.h
+++ b/xen/include/xen/iommu.h
@@ -26,6 +26,9 @@
 #include <xen/spinlock.h>
 #include <public/domctl.h>
 #include <public/hvm/ioreq.h>
+#ifdef CONFIG_ACPI
+#include <asm/acpi.h>
+#endif
 #include <asm/device.h>
 
 TYPE_SAFE(uint64_t, dfn);
@@ -219,7 +222,8 @@ int iommu_dt_domain_init(struct domain *d);
 int iommu_release_dt_devices(struct domain *d);
 
 /*
- * Helper to add master device to the IOMMU using generic IOMMU DT bindings.
+ * Helpers to add master device to the IOMMU using generic (PCI-)IOMMU
+ * DT bindings.
  *
  * Return values:
  *  0 : device is protected by an IOMMU
@@ -228,12 +232,28 @@ int iommu_release_dt_devices(struct domain *d);
  *      (IOMMU is not enabled/present or device is not connected to it).
  */
 int iommu_add_dt_device(struct dt_device_node *np);
+int iommu_add_dt_pci_sideband_ids(struct pci_dev *pdev);
 
 int iommu_do_dt_domctl(struct xen_domctl *, struct domain *,
                        XEN_GUEST_HANDLE_PARAM(xen_domctl_t));
 
+#else /* !HAS_DEVICE_TREE */
+static inline int iommu_add_dt_pci_sideband_ids(struct pci_dev *pdev)
+{
+    return 0;
+}
 #endif /* HAS_DEVICE_TREE */
 
+static inline int iommu_add_pci_sideband_ids(struct pci_dev *pdev)
+{
+    int ret = 0;
+#ifdef CONFIG_ACPI
+    if ( acpi_disabled )
+#endif
+        ret = iommu_add_dt_pci_sideband_ids(pdev);
+    return ret;
+}
+
 struct page_info;
 
 /*
-- 
2.40.1