[PATCH v3 10/17] xen/arm: Add cmdline boot option "pci-passthrough = <boolean>"

[Rahul Singh <rahul.singh@xxxxxxx>]

Add cmdline boot option "pci-passthrough = = <boolean>" to enable or
disable the PCI passthrough support on ARM.

Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx>
---
Change in v3:
- Remove "define pci_passthrough_enabled (false)"
- Fixed coding style and minor comment
Change in v2:
- Add option in xen-command-line.pandoc
- Change pci option to pci-passthrough
- modify option from custom_param to boolean param
---
 docs/misc/xen-command-line.pandoc |  7 +++++++
 xen/arch/arm/pci/pci.c            | 14 ++++++++++++++
 xen/common/physdev.c              |  6 ++++++
 xen/include/asm-arm/pci.h         | 11 +++++++++++
 xen/include/asm-x86/pci.h         |  8 ++++++++
 5 files changed, 46 insertions(+)

diff --git a/docs/misc/xen-command-line.pandoc 
b/docs/misc/xen-command-line.pandoc
index 177e656f12..c8bf96ccf8 100644
--- a/docs/misc/xen-command-line.pandoc
+++ b/docs/misc/xen-command-line.pandoc
@@ -1808,6 +1808,13 @@ All numbers specified must be hexadecimal ones.
 
 This option can be specified more than once (up to 8 times at present).
 
+### pci-passthrough (arm)
+> `= <boolean>`
+
+> Default: `false`
+
+Flag to enable or disable support for PCI passthrough
+
 ### pcid (x86)
 > `= <boolean> | xpti=<bool>`
 
diff --git a/xen/arch/arm/pci/pci.c b/xen/arch/arm/pci/pci.c
index e359bab9ea..84d8f0d634 100644
--- a/xen/arch/arm/pci/pci.c
+++ b/xen/arch/arm/pci/pci.c
@@ -16,6 +16,7 @@
 #include <xen/device_tree.h>
 #include <xen/errno.h>
 #include <xen/init.h>
+#include <xen/param.h>
 #include <xen/pci.h>
 
 /*
@@ -62,8 +63,21 @@ static int __init acpi_pci_init(void)
 }
 #endif
 
+/*
+ * By default pci passthrough is disabled
+ */
+bool __read_mostly pci_passthrough_enabled = false;
+boolean_param("pci-passthrough", pci_passthrough_enabled);
+
 static int __init pci_init(void)
 {
+    /*
+     * Enable PCI passthrough when has been enabled explicitly
+     * (pci-passthrough=on)
+     */
+    if ( !pci_passthrough_enabled )
+        return 0;
+
     pci_segments_init();
 
     if ( acpi_disabled )
diff --git a/xen/common/physdev.c b/xen/common/physdev.c
index 20a5530269..2d5fc886fc 100644
--- a/xen/common/physdev.c
+++ b/xen/common/physdev.c
@@ -19,6 +19,9 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
         struct pci_dev_info pdev_info;
         nodeid_t node;
 
+        if ( !is_pci_passthrough_enabled() )
+            return -ENOSYS;
+
         ret = -EFAULT;
         if ( copy_from_guest(&add, arg, 1) != 0 )
             break;
@@ -54,6 +57,9 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
     case PHYSDEVOP_pci_device_remove: {
         struct physdev_pci_device dev;
 
+        if ( !is_pci_passthrough_enabled() )
+            return -ENOSYS;
+
         ret = -EFAULT;
         if ( copy_from_guest(&dev, arg, 1) != 0 )
             break;
diff --git a/xen/include/asm-arm/pci.h b/xen/include/asm-arm/pci.h
index 7dd9eb3dba..0cf849e26f 100644
--- a/xen/include/asm-arm/pci.h
+++ b/xen/include/asm-arm/pci.h
@@ -19,14 +19,25 @@
 
 #define pci_to_dev(pcidev) (&(pcidev)->arch.dev)
 
+extern bool_t pci_passthrough_enabled;
+
 /* Arch pci dev struct */
 struct arch_pci_dev {
     struct device dev;
 };
 
+static always_inline bool is_pci_passthrough_enabled(void)
+{
+    return pci_passthrough_enabled;
+}
 #else   /*!CONFIG_HAS_PCI*/
 
 struct arch_pci_dev { };
 
+static always_inline bool is_pci_passthrough_enabled(void)
+{
+    return false;
+}
+
 #endif  /*!CONFIG_HAS_PCI*/
 #endif /* __ARM_PCI_H__ */
diff --git a/xen/include/asm-x86/pci.h b/xen/include/asm-x86/pci.h
index cc05045e9c..3f806ce7a8 100644
--- a/xen/include/asm-x86/pci.h
+++ b/xen/include/asm-x86/pci.h
@@ -32,4 +32,12 @@ bool_t pci_ro_mmcfg_decode(unsigned long mfn, unsigned int 
*seg,
 extern int pci_mmcfg_config_num;
 extern struct acpi_mcfg_allocation *pci_mmcfg_config;
 
+/*
+ * Unlike ARM, PCI passthrough is always enabled for x86.
+ */
+static always_inline bool is_pci_passthrough_enabled(void)
+{
+    return true;
+}
+
 #endif /* __X86_PCI_H__ */
-- 
2.17.1