x86/NUMA: cleanup

- constification
- prefer container_of() over casts
- check original pointer against NULL instead of the container_of()
  result

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/srat.c
+++ b/xen/arch/x86/srat.c
@@ -205,7 +205,7 @@ void __init acpi_numa_slit_init(struct a
 
 /* Callback for Proximity Domain -> x2APIC mapping */
 void __init
-acpi_numa_x2apic_affinity_init(struct acpi_srat_x2apic_cpu_affinity *pa)
+acpi_numa_x2apic_affinity_init(const struct acpi_srat_x2apic_cpu_affinity *pa)
 {
 	unsigned pxm;
 	nodeid_t node;
@@ -241,7 +241,7 @@ acpi_numa_x2apic_affinity_init(struct ac
 
 /* Callback for Proximity Domain -> LAPIC mapping */
 void __init
-acpi_numa_processor_affinity_init(struct acpi_srat_cpu_affinity *pa)
+acpi_numa_processor_affinity_init(const struct acpi_srat_cpu_affinity *pa)
 {
 	unsigned pxm;
 	nodeid_t node;
@@ -276,7 +276,7 @@ acpi_numa_processor_affinity_init(struct
 
 /* Callback for parsing of the Proximity Domain <-> Memory Area mappings */
 void __init
-acpi_numa_memory_affinity_init(struct acpi_srat_mem_affinity *ma)
+acpi_numa_memory_affinity_init(const struct acpi_srat_mem_affinity *ma)
 {
 	u64 start, end;
 	unsigned pxm;
--- a/xen/drivers/acpi/numa.c
+++ b/xen/drivers/acpi/numa.c
@@ -124,10 +124,11 @@ static int __init
 acpi_parse_x2apic_affinity(struct acpi_subtable_header *header,
 			   const unsigned long end)
 {
-	struct acpi_srat_x2apic_cpu_affinity *processor_affinity;
+	const struct acpi_srat_x2apic_cpu_affinity *processor_affinity
+		= container_of(header, struct acpi_srat_x2apic_cpu_affinity,
+			       header);
 
-	processor_affinity = (struct acpi_srat_x2apic_cpu_affinity *)header;
-	if (!processor_affinity)
+	if (!header)
 		return -EINVAL;
 
 	acpi_table_print_srat_entry(header);
@@ -139,13 +140,13 @@ acpi_parse_x2apic_affinity(struct acpi_s
 }
 
 static int __init
-acpi_parse_processor_affinity(struct acpi_subtable_header * header,
+acpi_parse_processor_affinity(struct acpi_subtable_header *header,
 			      const unsigned long end)
 {
-	struct acpi_srat_cpu_affinity *processor_affinity
+	const struct acpi_srat_cpu_affinity *processor_affinity
 		= container_of(header, struct acpi_srat_cpu_affinity, header);
 
-	if (!processor_affinity)
+	if (!header)
 		return -EINVAL;
 
 	acpi_table_print_srat_entry(header);
@@ -157,13 +158,13 @@ acpi_parse_processor_affinity(struct acp
 }
 
 static int __init
-acpi_parse_memory_affinity(struct acpi_subtable_header * header,
+acpi_parse_memory_affinity(struct acpi_subtable_header *header,
 			   const unsigned long end)
 {
-	struct acpi_srat_mem_affinity *memory_affinity
+	const struct acpi_srat_mem_affinity *memory_affinity
 		= container_of(header, struct acpi_srat_mem_affinity, header);
 
-	if (!memory_affinity)
+	if (!header)
 		return -EINVAL;
 
 	acpi_table_print_srat_entry(header);
--- a/xen/include/xen/acpi.h
+++ b/xen/include/xen/acpi.h
@@ -76,9 +76,9 @@ void acpi_table_print_srat_entry (struct
 
 /* the following four functions are architecture-dependent */
 void acpi_numa_slit_init (struct acpi_table_slit *slit);
-void acpi_numa_processor_affinity_init (struct acpi_srat_cpu_affinity *pa);
-void acpi_numa_x2apic_affinity_init(struct acpi_srat_x2apic_cpu_affinity *pa);
-void acpi_numa_memory_affinity_init (struct acpi_srat_mem_affinity *ma);
+void acpi_numa_processor_affinity_init(const struct acpi_srat_cpu_affinity *);
+void acpi_numa_x2apic_affinity_init(const struct acpi_srat_x2apic_cpu_affinity *);
+void acpi_numa_memory_affinity_init(const struct acpi_srat_mem_affinity *);
 void acpi_numa_arch_fixup(void);
 
 #ifdef CONFIG_ACPI_HOTPLUG_CPU