[PATCH for-5.0 7/8] acpi: cpuhp: add CPHP_GET_CPU_ID_CMD command

[Igor Mammedov <imammedo@redhat.com>]

Extend CPU hotplug interface to return architecture specific
identifier for current CPU in 2 registers:
 - lower 32 bits existing ACPI_CPU_CMD_DATA_OFFSET_RW
 - upper 32 bits in new ACPI_CPU_CMD_DATA2_OFFSET_R at
   offset 0.

Target user is UEFI firmware, which needs a way to enumerate
all CPUs (including possible CPUs) to allocate and initialize
CPU structures on boot.
(for x86: it needs APIC ID and later command will be used to
retrieve ARM's MPIDR which serves the similar to APIC ID purpose)

The new ACPI_CPU_CMD_DATA2_OFFSET_R register will also be used
to detect presence of modern CPU hotplug, which will be described
in follow up patch.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
v1:
 - s/ACPI_CPU_CMD_DATA2_OFFSET_RW/ACPI_CPU_CMD_DATA2_OFFSET_R/.
---
 docs/specs/acpi_cpu_hotplug.txt | 10 ++++++++--
 hw/acpi/cpu.c                   | 15 +++++++++++++++
 hw/acpi/trace-events            |  1 +
 3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/docs/specs/acpi_cpu_hotplug.txt b/docs/specs/acpi_cpu_hotplug.txt
index 58c16c6..bb33144 100644
--- a/docs/specs/acpi_cpu_hotplug.txt
+++ b/docs/specs/acpi_cpu_hotplug.txt
@@ -44,7 +44,11 @@ keeps the current value.
 
 read access:
     offset:
-    [0x0-0x3] reserved
+    [0x0-0x3] Command data 2: (DWORD access)
+              if last stored 'Command field' value:
+                  3: upper 32 bits of architecture specific identifying CPU value
+                     (n x86 case: 0x0)
+                  other values: reserved
     [0x4] CPU device status fields: (1 byte access)
         bits:
            0: Device is enabled and may be used by guest
@@ -96,7 +100,9 @@ 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.
-            other values: reserved
+              3: lower 32 bit of architecture specific identifier
+                 (in x86 case: APIC ID)
+              other values: reserved
 
     Typical usecases:
         - Get a cpu with pending event
diff --git a/hw/acpi/cpu.c b/hw/acpi/cpu.c
index 87f30a3..87813ce 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_R 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 = cdev->arch_id & 0xFFFFFFFF;
+           break;
         default:
            break;
         }
         trace_cpuhp_acpi_read_cmd_data(cpu_st->selector, val);
         break;
+    case ACPI_CPU_CMD_DATA2_OFFSET_R:
+        switch (cpu_st->command) {
+        case CPHP_GET_CPU_ID_CMD:
+           val = 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 96b8273..afbc77d 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"]"
-- 
2.7.4