[PATCH] xen/arm: vpci: Remove PCI I/O ranges property value

[Rahul Singh <rahul.singh@xxxxxxx>]

IO ports on ARM don't exist so all IO ports related hypercalls are going
to fail on ARM when we passthrough a PCI device.
Failure of xc_domain_ioport_permission(..) would turn into a critical
failure at domain creation. We need to avoid this outcome, instead we
want to continue with domain creation as normal even if
xc_domain_ioport_permission(..) fails. XEN_DOMCTL_ioport_permission
is not implemented on ARM so it would return -ENOSYS.

To solve above issue remove PCI I/O ranges property value from dom0
device tree node so that dom0 linux will not allocate I/O space for PCI
devices if pci-passthrough is enabled.

Another valid reason to remove I/O ranges is that PCI I/O space are not
mapped to dom0 when PCI passthrough is enabled, also there is no vpci
trap handler register for IO bar.

Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx>
---
 xen/arch/arm/domain_build.c   | 14 +++++++
 xen/common/device_tree.c      | 72 +++++++++++++++++++++++++++++++++++
 xen/include/xen/device_tree.h | 10 +++++
 3 files changed, 96 insertions(+)

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index d02bacbcd1..60f6b2c73b 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -749,6 +749,11 @@ static int __init write_properties(struct domain *d, 
struct kernel_info *kinfo,
                 continue;
         }
 
+        if ( is_pci_passthrough_enabled() &&
+                dt_device_type_is_equal(node, "pci") )
+            if ( dt_property_name_is_equal(prop, "ranges") )
+                continue;
+
         res = fdt_property(kinfo->fdt, prop->name, prop_data, prop_len);
 
         if ( res )
@@ -769,6 +774,15 @@ static int __init write_properties(struct domain *d, 
struct kernel_info *kinfo,
             if ( res )
                 return res;
         }
+
+        /*
+         * PCI IO bar are not mapped to dom0 when PCI passthrough is enabled,
+         * also there is no trap handler registered for IO bar therefor remove
+         * the IO range property from the device tree node for dom0.
+         */
+        res = dt_pci_remove_io_ranges(kinfo->fdt, node);
+        if ( res )
+            return res;
     }
 
     /*
diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
index 4aae281e89..9fa25f6723 100644
--- a/xen/common/device_tree.c
+++ b/xen/common/device_tree.c
@@ -2195,6 +2195,78 @@ int dt_get_pci_domain_nr(struct dt_device_node *node)
     return (u16)domain;
 }
 
+int dt_pci_remove_io_ranges(void *fdt, const struct dt_device_node *dev)
+{
+    const struct dt_device_node *parent = NULL;
+    const struct dt_bus *bus, *pbus;
+    unsigned int rlen;
+    int na, ns, pna, pns, rone, ret;
+    const __be32 *ranges;
+    __be32 regs[((GUEST_ROOT_ADDRESS_CELLS * 2) + GUEST_ROOT_SIZE_CELLS + 1)
+               * 2];
+    __be32 *addr = &regs[0];
+
+    bus = dt_match_bus(dev);
+    if ( !bus )
+        return 0; /* device is not a bus */
+
+    parent = dt_get_parent(dev);
+    if ( parent == NULL )
+        return -EINVAL;
+
+    ranges = dt_get_property(dev, "ranges", &rlen);
+    if ( ranges == NULL )
+    {
+        printk(XENLOG_ERR "DT: no ranges; cannot enumerate %s\n",
+               dev->full_name);
+        return -EINVAL;
+    }
+    if ( rlen == 0 ) /* Nothing to do */
+        return 0;
+
+    bus->count_cells(dev, &na, &ns);
+    if ( !DT_CHECK_COUNTS(na, ns) )
+    {
+        printk(XENLOG_ERR "dt_parse: Bad cell count for device %s\n",
+                  dev->full_name);
+        return -EINVAL;
+    }
+    pbus = dt_match_bus(parent);
+    if ( pbus == NULL )
+    {
+        printk("DT: %s is not a valid bus\n", parent->full_name);
+        return -EINVAL;
+    }
+
+    pbus->count_cells(dev, &pna, &pns);
+    if ( !DT_CHECK_COUNTS(pna, pns) )
+    {
+        printk(XENLOG_ERR "dt_parse: Bad cell count for parent %s\n",
+               dev->full_name);
+        return -EINVAL;
+    }
+    /* Now walk through the ranges */
+    rlen /= 4;
+    rone = na + pna + ns;
+
+    for ( ; rlen >= rone; rlen -= rone, ranges += rone )
+    {
+        unsigned int flags = bus->get_flags(ranges);
+        if ( flags & IORESOURCE_IO )
+            continue;
+
+        memcpy(addr, ranges, 4 * rone);
+
+        addr += rone;
+    }
+
+    ret = fdt_property(fdt, "ranges", regs, sizeof(regs));
+    if ( ret )
+        return ret;
+
+    return 0;
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/xen/include/xen/device_tree.h b/xen/include/xen/device_tree.h
index fd6cd00b43..ad2e905595 100644
--- a/xen/include/xen/device_tree.h
+++ b/xen/include/xen/device_tree.h
@@ -849,6 +849,16 @@ int dt_count_phandle_with_args(const struct dt_device_node 
*np,
  */
 int dt_get_pci_domain_nr(struct dt_device_node *node);
 
+/**
+ * dt_get_remove_io_range - Remove the PCI I/O range property value.
+ * @fdt: Pointer to the file descriptor tree.
+ * @node: Device tree node.
+ *
+ * This function will remove the PCI IO range property from the PCI device tree
+ * node.
+ */
+int dt_pci_remove_io_ranges(void *fdt, const struct dt_device_node *node);
+
 struct dt_device_node *dt_find_node_by_phandle(dt_phandle handle);
 
 #ifdef CONFIG_DEVICE_TREE_DEBUG
-- 
2.25.1