acpi: cpuhp: introduce 'Command data 2' field

No functional change in practice, patch only aims to properly
document (in spec and code) intended usage of the reserved space.

The new field is to be used for 2 purposes:
  - detection of modern CPU hotplug interface using
    CPHP_GET_NEXT_CPU_WITH_EVENT_CMD command.
    procedure will be described in follow up patch:
      "acpi: cpuhp: spec: add typical usecases"
  - for returning upper 32 bits of architecture specific CPU ID,
    for new CPHP_GET_CPU_ID_CMD command added by follow up patch:
      "acpi: cpuhp: add CPHP_GET_CPU_ID_CMD command"

Change is backward compatible with 4.2 and older machines, as field was
unconditionally reserved and always returned 0x0 if modern CPU hotplug
interface was enabled.

Signed-off-by: Igor Mammedov <[email protected]>
Message-Id: <1575896942[email protected]>
Reviewed-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>
Reviewed-by: Laszlo Ersek <[email protected]>

diff --git a/docs/specs/acpi_cpu_hotplug.txt b/docs/specs/acpi_cpu_hotplug.txt
index 8fb9ad22e6eb929ece161cbc71a30772af3cda76..9879f9ef7e2272646a99d4695b6dd417c64c37ee 100644 (file)
--- a/docs/specs/acpi_cpu_hotplug.txt
+++ b/docs/specs/acpi_cpu_hotplug.txt
@@ -44,7 +44,10 @@ keeps the current value.
 
 read access:
     offset:
-    [0x0-0x3] reserved
+    [0x0-0x3] Command data 2: (DWORD access)
+              if value last stored in 'Command field':
+                0: reads as 0x0
+                other values: reserved
     [0x4] CPU device status fields: (1 byte access)
         bits:
            0: Device is enabled and may be used by guest

diff --git a/hw/acpi/cpu.c b/hw/acpi/cpu.c
index 87f30a31d77b8dbc1c1201a33480eacc11336d66..d475c06953c0b225dfee924abd34be194b06535d 100644 (file)
--- a/hw/acpi/cpu.c
+++ b/hw/acpi/cpu.c
@@ -12,6 +12,7 @@
 #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,
@@ -79,6 +80,16 @@ static uint64_t cpu_hotplug_rd(void *opaque, hwaddr addr, unsigned size)
         }
         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_NEXT_CPU_WITH_EVENT_CMD:
+           val = 0;
+           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 96b8273297a4647d66ea4606849660c6a2d86dc7..afbc77de1c716dbb7addd933f356870e381c04fc 100644 (file)
--- 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"]"