[PATCH v6 2/7] xen/arm: add pci-domain for disabled devices

[Oleksandr Andrushchenko <andr2000@gmail.com>]

From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>

If a PCI host bridge device is present in the device tree, but is
disabled, then its PCI host bridge driver was not instantiated.
This results in the failure of the pci_get_host_bridge_segment()
and the following panic during Xen start:

(XEN) Device tree generation failed (-22).
(XEN)
(XEN) ****************************************
(XEN) Panic on CPU 0:
(XEN) Could not set up DOM0 guest OS
(XEN) ****************************************

Fix this by adding "linux,pci-domain" property for all device tree nodes
which have "pci" device type, so we know which segments will be used by
the guest for which bridges.

Fixes: 4cfab4425d39 ("xen/arm: Add linux,pci-domain property for hwdom if not available.")

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>

---
New in v6
---
 xen/arch/arm/domain_build.c        | 15 ++++++++++++++-
 xen/arch/arm/pci/pci-host-common.c |  2 +-
 xen/include/asm-arm/pci.h          |  8 ++++++++
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 491f5e2c316e..f7fcb1400c19 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -753,9 +753,22 @@ static int __init write_properties(struct domain *d, struct kernel_info *kinfo,
         {
             uint16_t segment;
 
+            /*
+             * The node doesn't have "linux,pci-domain" property and it is
+             * possible that:
+             *  - Xen only has drivers for a part of the host bridges
+             *  - some host bridges are disabled
+             * Make sure we insert the correct "linux,pci-domain" property
+             * in any case, so we know which segments will be used
+             * by Linux for which bridges.
+             */
             res = pci_get_host_bridge_segment(node, &segment);
             if ( res < 0 )
-                return res;
+            {
+                segment = pci_get_new_domain_nr();
+                printk(XENLOG_DEBUG "Assigned segment %d to %s\n",
+                       segment, node->full_name);
+            }
 
             res = fdt_property_cell(kinfo->fdt, "linux,pci-domain", segment);
             if ( res )
diff --git a/xen/arch/arm/pci/pci-host-common.c b/xen/arch/arm/pci/pci-host-common.c
index d8cbaaaba654..47104b22b221 100644
--- a/xen/arch/arm/pci/pci-host-common.c
+++ b/xen/arch/arm/pci/pci-host-common.c
@@ -137,7 +137,7 @@ void pci_add_host_bridge(struct pci_host_bridge *bridge)
     list_add_tail(&bridge->node, &pci_host_bridges);
 }
 
-static int pci_get_new_domain_nr(void)
+int pci_get_new_domain_nr(void)
 {
     return atomic_inc_return(&domain_nr);
 }
diff --git a/xen/include/asm-arm/pci.h b/xen/include/asm-arm/pci.h
index 81273e0d87ac..c20eba643d86 100644
--- a/xen/include/asm-arm/pci.h
+++ b/xen/include/asm-arm/pci.h
@@ -108,6 +108,8 @@ static always_inline bool is_pci_passthrough_enabled(void)
 
 void arch_pci_init_pdev(struct pci_dev *pdev);
 
+int pci_get_new_domain_nr(void);
+
 #else   /*!CONFIG_HAS_PCI*/
 
 struct arch_pci_dev { };
@@ -128,5 +130,11 @@ static inline int pci_get_host_bridge_segment(const struct dt_device_node *node,
     return -EINVAL;
 }
 
+static inline int pci_get_new_domain_nr(void)
+{
+    ASSERT_UNREACHABLE();
+    return -1;
+}
+
 #endif  /*!CONFIG_HAS_PCI*/
 #endif /* __ARM_PCI_H__ */
-- 
2.25.1