[RFC 3/3] acpi: cpuhp: add CPHP_GET_CPU_ID_CMD command

[Igor Mammedov]

Extend CPU hotplug interface to return architecture specific
identifier for current CPU (in case of x86, it's APIC ID).

Signed-off-by: Igor Mammedov <address@hidden>
---
TODO:
  * cripple it to behave old way on old machine types so that
    new firmware started on new QEMU won't see a difference
    when migrated to an old QEMU (i.e. QEMU that doesn't support
    this command)
---
 docs/specs/acpi_cpu_hotplug.txt | 10 +++++++++-
 hw/acpi/cpu.c                   | 15 +++++++++++++++
 hw/acpi/trace-events            |  1 +
 3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/docs/specs/acpi_cpu_hotplug.txt b/docs/specs/acpi_cpu_hotplug.txt
index 43c5a193f0..0438678249 100644
--- a/docs/specs/acpi_cpu_hotplug.txt
+++ b/docs/specs/acpi_cpu_hotplug.txt
@@ -32,7 +32,9 @@ Register block size:
 
 read access:
     offset:
-    [0x0-0x3] reserved
+    [0x0-0x3] Command data 2: (DWORD access)
+              upper 32 bit of 'Command data' if returned data value is 64 bit.
+              in case of error or unsupported command reads is 0x0
     [0x4] CPU device status fields: (1 byte access)
         bits:
            0: Device is enabled and may be used by guest
@@ -87,6 +89,8 @@ write access:
               2: stores value into OST status register, triggers
                  ACPI_DEVICE_OST QMP event from QEMU to external applications
                  with current values of OST event and status registers.
+              3: OSPM reads architecture specific value identifying CPU
+                 (x86: APIC ID)
             other values: reserved
 
 Selecting CPU device beyond possible range has no effect on platform:
@@ -115,3 +119,7 @@ Typical usecases:
      5.2 if 'Command data' register has not changed, there is not CPU
          corresponding to iterator value and the last valid iterator value
          equals to 'max_cpus' + 1
+   - Get architecture specific id for a CPU
+     1. pick a CPU to read from using 'CPU selector' register
+     2. write 0x3 int0 'Command field' register
+     3. read architecture specific id from 'Command data' register
diff --git a/hw/acpi/cpu.c b/hw/acpi/cpu.c
index 87f30a31d7..701542d860 100644
--- a/hw/acpi/cpu.c
+++ b/hw/acpi/cpu.c
@@ -12,11 +12,13 @@
 #define ACPI_CPU_FLAGS_OFFSET_RW 4
 #define ACPI_CPU_CMD_OFFSET_WR 5
 #define ACPI_CPU_CMD_DATA_OFFSET_RW 8
+#define ACPI_CPU_CMD_DATA2_OFFSET_RW 0
 
 enum {
     CPHP_GET_NEXT_CPU_WITH_EVENT_CMD = 0,
     CPHP_OST_EVENT_CMD = 1,
     CPHP_OST_STATUS_CMD = 2,
+    CPHP_GET_CPU_ID_CMD = 3,
     CPHP_CMD_MAX
 };
 
@@ -74,11 +76,24 @@ static uint64_t cpu_hotplug_rd(void *opaque, hwaddr addr, 
unsigned size)
         case CPHP_GET_NEXT_CPU_WITH_EVENT_CMD:
            val = cpu_st->selector;
            break;
+        case CPHP_GET_CPU_ID_CMD:
+           val = cpu_to_le64(cdev->arch_id) & 0xFFFFFFFF;
+           break;
         default:
            break;
         }
         trace_cpuhp_acpi_read_cmd_data(cpu_st->selector, val);
         break;
+    case ACPI_CPU_CMD_DATA2_OFFSET_RW:
+        switch (cpu_st->command) {
+        case CPHP_GET_CPU_ID_CMD:
+           val = cpu_to_le64(cdev->arch_id) >> 32;
+           break;
+        default:
+           break;
+        }
+        trace_cpuhp_acpi_read_cmd_data2(cpu_st->selector, val);
+        break;
     default:
         break;
     }
diff --git a/hw/acpi/trace-events b/hw/acpi/trace-events
index 96b8273297..afbc77de1c 100644
--- a/hw/acpi/trace-events
+++ b/hw/acpi/trace-events
@@ -23,6 +23,7 @@ cpuhp_acpi_read_flags(uint32_t idx, uint8_t flags) 
"idx[0x%"PRIx32"] flags: 0x%"
 cpuhp_acpi_write_idx(uint32_t idx) "set active cpu idx: 0x%"PRIx32
 cpuhp_acpi_write_cmd(uint32_t idx, uint8_t cmd) "idx[0x%"PRIx32"] cmd: 
0x%"PRIx8
 cpuhp_acpi_read_cmd_data(uint32_t idx, uint32_t data) "idx[0x%"PRIx32"] data: 
0x%"PRIx32
+cpuhp_acpi_read_cmd_data2(uint32_t idx, uint32_t data) "idx[0x%"PRIx32"] data: 
0x%"PRIx32
 cpuhp_acpi_cpu_has_events(uint32_t idx, bool ins, bool rm) "idx[0x%"PRIx32"] 
inserting: %d, removing: %d"
 cpuhp_acpi_clear_inserting_evt(uint32_t idx) "idx[0x%"PRIx32"]"
 cpuhp_acpi_clear_remove_evt(uint32_t idx) "idx[0x%"PRIx32"]"
-- 
2.18.1