From: Stewart Hildebrand <stewart.hildebrand@amd.com>

Enable the use of IOMMU + PCI in dom0 without having to specify
"pci-passthrough=yes". We rely on dom0 to initialize the PCI controller
and perform a PHYSDEVOP_pci_device_add call to add each device to SMMU.

Enable pci_init() for initializing Xen's internal PCI subsystem, and
allow PHYSDEVOP_pci_device_add when pci-passthrough is disabled.

Signed-off-by: Stewart Hildebrand <stewart.hildebrand@amd.com>
Signed-off-by: Mykyta Poturai <mykyta_poturai@epam.com>
---
hmm. Since
  dec9e02f3190 ("xen: avoid generation of stub <asm/pci.h> header")
Should we also move is_pci_passthrough_enabled() back to xen/arch/arm/include/asm/pci.h ?
Not sure if PPC/RISC-V will plan on using this check.

v8-v9:
* move iommu_enabled check inside is_pci_passthrough_enabled()

v7->v8:
* bring back x86 definition of is_pci_passthrough_enabled()

v6->v7:
* remove x86 definition of is_pci_passthrough_enabled()
* update comments
* make pci_physdev_op checks stricter

v5->v6:
* new patch - this effectively replaces
  ("Revert "xen/arm: Add cmdline boot option "pci-passthrough = <boolean>""")
---
 xen/arch/arm/domain_build.c    |  2 +-
 xen/arch/arm/include/asm/pci.h |  5 +----
 xen/arch/arm/pci/pci.c         | 11 ++++++++++-
 xen/arch/x86/include/asm/pci.h |  2 +-
 xen/drivers/pci/physdev.c      |  4 ++--
 xen/include/xen/pci.h          |  2 +-
 6 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 7b47abade1..fbd6db9438 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -526,7 +526,7 @@ static int __init handle_linux_pci_domain(struct kernel_info *kinfo,
     uint16_t segment;
     int res;
 
-    if ( !is_pci_passthrough_enabled() )
+    if ( !is_pci_passthrough_enabled(false) )
         return 0;
 
     if ( !dt_device_type_is_equal(node, "pci") )
diff --git a/xen/arch/arm/include/asm/pci.h b/xen/arch/arm/include/asm/pci.h
index 7f77226c9b..3ae85b4666 100644
--- a/xen/arch/arm/include/asm/pci.h
+++ b/xen/arch/arm/include/asm/pci.h
@@ -111,10 +111,7 @@ pci_find_host_bridge_node(const struct pci_dev *pdev);
 int pci_get_host_bridge_segment(const struct dt_device_node *node,
                                 uint16_t *segment);
 
-static always_inline bool is_pci_passthrough_enabled(void)
-{
-    return pci_passthrough_enabled;
-}
+bool is_pci_passthrough_enabled(bool dom0);
 
 void arch_pci_init_pdev(struct pci_dev *pdev);
 
diff --git a/xen/arch/arm/pci/pci.c b/xen/arch/arm/pci/pci.c
index 78b97beaef..79bb8728a4 100644
--- a/xen/arch/arm/pci/pci.c
+++ b/xen/arch/arm/pci/pci.c
@@ -16,9 +16,18 @@
 #include <xen/device_tree.h>
 #include <xen/errno.h>
 #include <xen/init.h>
+#include <xen/iommu.h>
 #include <xen/param.h>
 #include <xen/pci.h>
 
+bool is_pci_passthrough_enabled(bool dom0)
+{
+    if ( dom0 )
+        return pci_passthrough_enabled || iommu_enabled;
+
+    return pci_passthrough_enabled;
+}
+
 /*
  * PIRQ event channels are not supported on Arm, so nothing to do.
  */
@@ -85,7 +94,7 @@ static int __init pci_init(void)
      * Enable PCI passthrough when has been enabled explicitly
      * (pci-passthrough=on).
      */
-    if ( !pci_passthrough_enabled )
+    if ( !is_pci_passthrough_enabled(true) )
         return 0;
 
     pci_segments_init();
diff --git a/xen/arch/x86/include/asm/pci.h b/xen/arch/x86/include/asm/pci.h
index fd5480d67d..bffeaa507d 100644
--- a/xen/arch/x86/include/asm/pci.h
+++ b/xen/arch/x86/include/asm/pci.h
@@ -50,7 +50,7 @@ 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)
+static always_inline bool is_pci_passthrough_enabled(__maybe_unused bool dom0)
 {
     return true;
 }
diff --git a/xen/drivers/pci/physdev.c b/xen/drivers/pci/physdev.c
index 0161a85e1e..18448b94b3 100644
--- a/xen/drivers/pci/physdev.c
+++ b/xen/drivers/pci/physdev.c
@@ -19,7 +19,7 @@ ret_t pci_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
         struct pci_dev_info pdev_info;
         nodeid_t node = NUMA_NO_NODE;
 
-        if ( !is_pci_passthrough_enabled() )
+        if ( !is_pci_passthrough_enabled(true) )
             return -EOPNOTSUPP;
 
         ret = -EFAULT;
@@ -57,7 +57,7 @@ ret_t pci_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() )
+        if ( !is_pci_passthrough_enabled(true) )
             return -EOPNOTSUPP;
 
         ret = -EFAULT;
diff --git a/xen/include/xen/pci.h b/xen/include/xen/pci.h
index f784e91160..c4a49cf584 100644
--- a/xen/include/xen/pci.h
+++ b/xen/include/xen/pci.h
@@ -74,7 +74,7 @@ typedef union {
 
 struct arch_pci_dev { };
 
-static inline bool is_pci_passthrough_enabled(void)
+static inline bool is_pci_passthrough_enabled(__maybe_unused bool dom0)
 {
     return false;
 }
-- 
2.34.1