pc: acpi-build: create CPU hotplug IO region dynamically

it replaces a static complied in DSDT MMIO region
for CPU hotplug with one created at runtime
leaving only truly static CPU hotplug related ASL
bits in DSDT.
It also puts CPU_HOTPLUG_RESOURCE_DEVICE into
PCI0 scope and reserves resources from it,
preparing for dropping manual hole punching
in PCI0._CRS.

Later it also would make easier to reuse current
ACPI CPU hotplug on other targets.

Also later it would be possible to move remaining
CPU hotplug ASL methods into build_ssdt() and
add all CPU hotplug related AML into SSDT only
when CPU hotplug is enabled, further reducing
ACPI tables blob if CPU hotplug isn't used.

impl. detail:
Windows XP can't handle /BSODs/ OperationRegion
declaration in DSDT when variable from SSDT is used
for specifying its address/length and also when
Field declared in DSDT with OperationRegion from
SSDT if DSDT is being parsed before SSDT.
But it works just fine when referencing named
fields from another table. Hence OperationRegion
and Field declaration are moved to SSDT to make
XP based editions work.

PS:
Later Windows editions seem to be fine with above
conditions.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/i386/acpi-build.c

@@ -101,6 +101,8 @@ typedef struct AcpiPmInfo {
     uint32_t gpe0_blk;
     uint32_t gpe0_blk_len;
     uint32_t io_base;
+    uint16_t cpu_hp_io_base;
+    uint16_t cpu_hp_io_len;
 } AcpiPmInfo;
 
 typedef struct AcpiMiscInfo {
@@ -176,12 +178,15 @@ static void acpi_get_pm_info(AcpiPmInfo *pm)
 
     if (piix) {
         obj = piix;
+        pm->cpu_hp_io_base = PIIX4_CPU_HOTPLUG_IO_BASE;
     }
     if (lpc) {
         obj = lpc;
+        pm->cpu_hp_io_base = ICH9_CPU_HOTPLUG_IO_BASE;
     }
     assert(obj);
 
+    pm->cpu_hp_io_len = ACPI_GPE_PROC_LEN;
     /* Fill in optional s3/s4 related properties */
     o = object_property_get_qobject(obj, ACPI_PM_PROP_S3_DISABLED, NULL);
     if (o) {
@@ -995,6 +1000,28 @@ build_ssdt(GArray *table_data, GArray *linker,
 
     sb_scope = aml_scope("_SB");
     {
+        /* create PCI0.PRES device and its _CRS to reserve CPU hotplug MMIO */
+        dev = aml_device("PCI0." stringify(CPU_HOTPLUG_RESOURCE_DEVICE));
+        aml_append(dev, aml_name_decl("_HID", aml_eisaid("PNP0A06")));
+        aml_append(dev,
+            aml_name_decl("_UID", aml_string("CPU Hotplug resources"))
+        );
+        /* device present, functioning, decoding, not shown in UI */
+        aml_append(dev, aml_name_decl("_STA", aml_int(0xB)));
+        crs = aml_resource_template();
+        aml_append(crs,
+            aml_io(aml_decode16, pm->cpu_hp_io_base, pm->cpu_hp_io_base, 1,
+                   pm->cpu_hp_io_len)
+        );
+        aml_append(dev, aml_name_decl("_CRS", crs));
+        aml_append(sb_scope, dev);
+        /* declare CPU hotplug MMIO region and PRS field to access it */
+        aml_append(sb_scope, aml_operation_region(
+            "PRST", aml_system_io, pm->cpu_hp_io_base, pm->cpu_hp_io_len));
+        field = aml_field("PRST", aml_byte_acc);
+        aml_append(field, aml_named_field("PRS", 256));
+        aml_append(sb_scope, field);
+
         /* build Processor object for each processor */
         for (i = 0; i < acpi_cpus; i++) {
             dev = aml_processor(i, 0, 0, "CP%.02X", i);

hw/i386/acpi-dsdt-cpu-hotplug.dsl

@@ -16,12 +16,12 @@
 /****************************************************************
  * CPU hotplug
  ****************************************************************/
-#define CPU_HOTPLUG_RESOURCE_DEVICE PRES
 
 Scope(\_SB) {
     /* Objects filled in by run-time generated SSDT */
     External(NTFY, MethodObj)
     External(CPON, PkgObj)
+    External(PRS, FieldUnitObj)
 
     /* Methods called by run-time generated SSDT Processor objects */
     Method(CPMA, 1, NotSerialized) {
@@ -54,10 +54,6 @@ Scope(\_SB) {
     }
 
 #define CPU_STATUS_LEN ACPI_GPE_PROC_LEN
-    OperationRegion(PRST, SystemIO, CPU_STATUS_BASE, CPU_STATUS_LEN)
-    Field(PRST, ByteAcc, NoLock, Preserve) {
-        PRS, 256
-    }
     Method(PRSC, 0) {
         // Local5 = active cpu bitmap
         Store(PRS, Local5)
@@ -91,15 +87,4 @@ Scope(\_SB) {
             Increment(Local0)
         }
     }
-
-    Device(CPU_HOTPLUG_RESOURCE_DEVICE) {
-        Name(_HID, EisaId("PNP0A06"))
-        Name(_UID, "CPU hotplug resources")
-
-        Name(_CRS, ResourceTemplate() {
-            IO(Decode16, CPU_STATUS_BASE, CPU_STATUS_BASE, 0, CPU_STATUS_LEN)
-        })
-
-        Name(_STA, 0xB) /* present, functioning, decoding, not shown in UI */
-    }
 }

include/hw/acpi/pc-hotplug.h

@@ -28,6 +28,7 @@
 
 #define ICH9_CPU_HOTPLUG_IO_BASE 0x0CD8
 #define PIIX4_CPU_HOTPLUG_IO_BASE 0xaf00
+#define CPU_HOTPLUG_RESOURCE_DEVICE PRES
 
 #define ACPI_MEMORY_HOTPLUG_IO_LEN 24
 #define ACPI_MEMORY_HOTPLUG_BASE 0x0a00