IOMMU/x86: remove indirection from certain IOMMU hook accesses

There's no need to go through an extra level of indirection. In order to
limit code churn, call sites using struct domain_iommu's platform_ops
don't get touched here, however.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Acked-by: Brian Woods <brian.woods@amd.com>

xen/drivers/passthrough/amd/pci_amd_iommu.c

@@ -29,6 +29,8 @@
 
 static bool_t __read_mostly init_done;
 
+static const struct iommu_ops amd_iommu_ops;
+
 struct amd_iommu *find_iommu_for_device(int seg, int bdf)
 {
     struct ivrs_mappings *ivrs_mappings = get_ivrs_mappings(seg);
@@ -182,6 +184,8 @@ int __init amd_iov_detect(void)
         return -ENODEV;
     }
 
+    iommu_ops = amd_iommu_ops;
+
     if ( amd_iommu_init() != 0 )
     {
         printk("AMD-Vi: Error initialization\n");
@@ -566,7 +570,7 @@ static void amd_dump_p2m_table(struct domain *d)
     amd_dump_p2m_table_level(hd->arch.root_table, hd->arch.paging_mode, 0, 0);
 }
 
-const struct iommu_ops amd_iommu_ops = {
+static const struct iommu_ops __initconstrel amd_iommu_ops = {
     .init = amd_iommu_domain_init,
     .hwdom_init = amd_iommu_hwdom_init,
     .add_device = amd_iommu_add_device,

xen/drivers/passthrough/vtd/extern.h

@@ -27,6 +27,7 @@
 
 struct pci_ats_dev;
 extern bool_t rwbf_quirk;
+extern const struct iommu_ops intel_iommu_ops;
 
 void print_iommu_regs(struct acpi_drhd_unit *drhd);
 void print_vtd_entries(struct iommu *iommu, int bus, int devfn, u64 gmfn);

xen/drivers/passthrough/vtd/intremap.c

@@ -897,6 +897,8 @@ int iommu_enable_x2apic_IR(void)
     else if ( !x2apic_enabled )
         return -EOPNOTSUPP;
 
+    iommu_ops = intel_iommu_ops;
+
     for_each_drhd_unit ( drhd )
     {
         iommu = drhd->iommu;

xen/drivers/passthrough/vtd/iommu.c

@@ -2299,6 +2299,8 @@ int __init intel_vtd_setup(void)
         goto error;
     }
 
+    iommu_ops = intel_iommu_ops;
+
     /* We enable the following features only if they are supported by all VT-d
      * engines: Snoop Control, DMA passthrough, Queued Invalidation, Interrupt
      * Remapping, and Posted Interrupt
@@ -2698,7 +2700,7 @@ static void vtd_dump_p2m_table(struct domain *d)
     vtd_dump_p2m_table_level(hd->arch.pgd_maddr, agaw_to_level(hd->arch.agaw), 0, 0);
 }
 
-const struct iommu_ops intel_iommu_ops = {
+const struct iommu_ops __initconstrel intel_iommu_ops = {
     .init = intel_iommu_domain_init,
     .hwdom_init = intel_iommu_hwdom_init,
     .add_device = intel_iommu_add_device,

xen/drivers/passthrough/x86/iommu.c

@@ -23,6 +23,8 @@
 #include <asm/hvm/io.h>
 #include <asm/setup.h>
 
+struct iommu_ops iommu_ops;
+
 void iommu_update_ire_from_apic(
     unsigned int apic, unsigned int reg, unsigned int value)
 {

xen/include/asm-x86/iommu.h

@@ -56,24 +56,15 @@ struct arch_iommu
     struct guest_iommu *g_iommu;
 };
 
-extern const struct iommu_ops intel_iommu_ops;
-extern const struct iommu_ops amd_iommu_ops;
 int intel_vtd_setup(void);
 int amd_iov_detect(void);
 
+extern struct iommu_ops iommu_ops;
+
 static inline const struct iommu_ops *iommu_get_ops(void)
 {
-    switch ( boot_cpu_data.x86_vendor )
-    {
-    case X86_VENDOR_INTEL:
-        return &intel_iommu_ops;
-    case X86_VENDOR_AMD:
-        return &amd_iommu_ops;
-    }
-
-    BUG();
-
-    return NULL;
+    BUG_ON(!iommu_ops.init);
+    return &iommu_ops;
 }
 
 static inline int iommu_hardware_setup(void)