[PATCH v3 1/2] xen/passthrough: Provide stub functions when !HAS_PASSTHROUGH

[Luca Fancellu <luca.fancellu@xxxxxxx>]

When Xen is built without HAS_PASSTHROUGH, there are some parts
in arm where iommu_* functions are called in the codebase, but
their implementation is under xen/drivers/passthrough that is
not built.

So provide some stub for these functions in order to build Xen
when !HAS_PASSTHROUGH, which is the case for example on systems
with MPU support.

For gnttab_need_iommu_mapping() in the Arm part, modify the macro
to use IS_ENABLED for the HAS_PASSTHROUGH Kconfig.

Fixes: 0388a5979b21 ("xen/arm: mpu: Introduce choice between MMU and MPU")
Signed-off-by: Luca Fancellu <luca.fancellu@xxxxxxx>
---
v3 Changes:
 - removed stub for iommu_use_hap_pt, another solution will be
   done for the instance in common arm code.
 - Moved a comment close to the macro it was referred to
 - add comment to iommu_domain_init() stub
 - modified commit message
 - Add fixes tag

v2 Changes:
 - modify gnttab_need_iommu_mapping to use IS_ENABLED
 - removed macro that didn't allow some of the parameter to be
   evaluated
 - Changed commit message
---
---
 xen/arch/arm/include/asm/grant_table.h |  5 +--
 xen/include/xen/iommu.h                | 48 +++++++++++++++++++++++++-
 2 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/xen/arch/arm/include/asm/grant_table.h 
b/xen/arch/arm/include/asm/grant_table.h
index d3c518a926b9..c5d87b60c4df 100644
--- a/xen/arch/arm/include/asm/grant_table.h
+++ b/xen/arch/arm/include/asm/grant_table.h
@@ -73,8 +73,9 @@ int replace_grant_host_mapping(uint64_t gpaddr, mfn_t frame,
 #define gnttab_status_gfn(d, t, i)                                       \
     page_get_xenheap_gfn(gnttab_status_page(t, i))
 
-#define gnttab_need_iommu_mapping(d)                    \
-    (is_domain_direct_mapped(d) && is_iommu_enabled(d))
+#define gnttab_need_iommu_mapping(d)                                     \
+    (IS_ENABLED(CONFIG_HAS_PASSTHROUGH) && is_domain_direct_mapped(d) && \
+     is_iommu_enabled(d))
 
 #endif /* __ASM_GRANT_TABLE_H__ */
 /*
diff --git a/xen/include/xen/iommu.h b/xen/include/xen/iommu.h
index 77a514019cc6..b6ba3adcbc8a 100644
--- a/xen/include/xen/iommu.h
+++ b/xen/include/xen/iommu.h
@@ -110,6 +110,8 @@ extern int8_t iommu_hwdom_reserved;
 
 extern unsigned int iommu_dev_iotlb_timeout;
 
+#ifdef CONFIG_HAS_PASSTHROUGH
+
 int iommu_setup(void);
 int iommu_hardware_setup(void);
 
@@ -122,6 +124,28 @@ int arch_iommu_domain_init(struct domain *d);
 void arch_iommu_check_autotranslated_hwdom(struct domain *d);
 void arch_iommu_hwdom_init(struct domain *d);
 
+#else
+
+static inline int iommu_setup(void)
+{
+    return -ENODEV;
+}
+
+static inline int iommu_domain_init(struct domain *d, unsigned int opts)
+{
+    /*
+     * When !HAS_PASSTHROUGH, iommu_enabled is set to false and the expected
+     * behaviour of this function is to return success in that case.
+     */
+    return 0;
+}
+
+static inline void iommu_hwdom_init(struct domain *d) {}
+
+static inline void iommu_domain_destroy(struct domain *d) {}
+
+#endif /* HAS_PASSTHROUGH */
+
 /*
  * The following flags are passed to map (applicable ones also to unmap)
  * operations, while some are passed back by lookup operations.
@@ -209,6 +233,8 @@ struct msi_msg;
 #ifdef CONFIG_HAS_DEVICE_TREE
 #include <xen/device_tree.h>
 
+#ifdef CONFIG_HAS_PASSTHROUGH
+
 int iommu_assign_dt_device(struct domain *d, struct dt_device_node *dev);
 int iommu_deassign_dt_device(struct domain *d, struct dt_device_node *dev);
 int iommu_dt_domain_init(struct domain *d);
@@ -238,6 +264,26 @@ int iommu_do_dt_domctl(struct xen_domctl *domctl, struct 
domain *d,
  */
 int iommu_remove_dt_device(struct dt_device_node *np);
 
+#else
+
+static inline int iommu_assign_dt_device(struct domain *d,
+                                         struct dt_device_node *dev)
+{
+    return -EINVAL;
+}
+
+static inline int iommu_add_dt_device(struct dt_device_node *np)
+{
+    return 1;
+}
+
+static inline int iommu_release_dt_devices(struct domain *d)
+{
+    return 0;
+}
+
+#endif /* HAS_PASSTHROUGH */
+
 #endif /* HAS_DEVICE_TREE */
 
 struct page_info;
@@ -383,12 +429,12 @@ struct domain_iommu {
 #define iommu_set_feature(d, f)   set_bit(f, dom_iommu(d)->features)
 #define iommu_clear_feature(d, f) clear_bit(f, dom_iommu(d)->features)
 
+#ifdef CONFIG_HAS_PASSTHROUGH
 /* Are we using the domain P2M table as its IOMMU pagetable? */
 #define iommu_use_hap_pt(d)       (IS_ENABLED(CONFIG_HVM) && \
                                    dom_iommu(d)->hap_pt_share)
 
 /* Does the IOMMU pagetable need to be kept synchronized with the P2M */
-#ifdef CONFIG_HAS_PASSTHROUGH
 #define need_iommu_pt_sync(d)     (dom_iommu(d)->need_sync)
 
 int iommu_do_domctl(struct xen_domctl *domctl, struct domain *d,
-- 
2.34.1