acpi: cpuhp: introduce 'firmware performs eject' status/control bits

Adds bit #4 to status/control field of CPU hotplug MMIO interface.
New bit will be used OSPM to mark CPUs as pending for removal by firmware,
when it calls _EJ0 method on CPU device node. Later on, when firmware
sees this bit set, it will perform CPU eject which will clear bit #4
as well.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20201207140739.3829993-3-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

docs/specs/acpi_cpu_hotplug.txt

@@ -56,8 +56,11 @@ read access:
               no device check event to OSPM was issued.
               It's valid only when bit 0 is set.
            2: Device remove event, used to distinguish device for which
-              no device eject request to OSPM was issued.
+              no device eject request to OSPM was issued. Firmware must
-           3-7: reserved and should be ignored by OSPM
+              ignore this bit.
+           3: reserved and should be ignored by OSPM
+           4: if set to 1, OSPM requests firmware to perform device eject.
+           5-7: reserved and should be ignored by OSPM
     [0x5-0x7] reserved
     [0x8] Command data: (DWORD access)
           contains 0 unless value last stored in 'Command field' is one of:
@@ -79,10 +82,16 @@ write access:
                selected CPU device
             2: if set to 1 clears device remove event, set by OSPM
                after it has emitted device eject request for the
-               selected CPU device
+               selected CPU device.
             3: if set to 1 initiates device eject, set by OSPM when it
-               triggers CPU device removal and calls _EJ0 method
+               triggers CPU device removal and calls _EJ0 method or by firmware
-            4-7: reserved, OSPM must clear them before writing to register
+               when bit #4 is set. In case bit #4 were set, it's cleared as
+               part of device eject.
+            4: if set to 1, OSPM hands over device eject to firmware.
+               Firmware shall issue device eject request as described above
+               (bit #3) and OSPM should not touch device eject bit (#3) in case
+               it's asked firmware to perform CPU device eject.
+            5-7: reserved, OSPM must clear them before writing to register
     [0x5] Command field: (1 byte access)
           value:
             0: selects a CPU device with inserting/removing events and

hw/acpi/cpu.c

@@ -71,6 +71,7 @@ static uint64_t cpu_hotplug_rd(void *opaque, hwaddr addr, unsigned size)
         val |= cdev->cpu ? 1 : 0;
         val |= cdev->is_inserting ? 2 : 0;
         val |= cdev->is_removing  ? 4 : 0;
+        val |= cdev->fw_remove  ? 16 : 0;
         trace_cpuhp_acpi_read_flags(cpu_st->selector, val);
         break;
     case ACPI_CPU_CMD_DATA_OFFSET_RW:
@@ -148,6 +149,14 @@ static void cpu_hotplug_wr(void *opaque, hwaddr addr, uint64_t data,
             hotplug_ctrl = qdev_get_hotplug_handler(dev);
             hotplug_handler_unplug(hotplug_ctrl, dev, NULL);
             object_unparent(OBJECT(dev));
+            cdev->fw_remove = false;
+        } else if (data & 16) {
+            if (!cdev->cpu || cdev->cpu == first_cpu) {
+                trace_cpuhp_acpi_fw_remove_invalid_cpu(cpu_st->selector);
+                break;
+            }
+            trace_cpuhp_acpi_fw_remove_cpu(cpu_st->selector);
+            cdev->fw_remove = true;
         }
         break;
     case ACPI_CPU_CMD_OFFSET_WR:
@@ -159,7 +168,8 @@ static void cpu_hotplug_wr(void *opaque, hwaddr addr, uint64_t data,
 
                 do {
                     cdev = &cpu_st->devs[iter];
-                    if (cdev->is_inserting || cdev->is_removing) {
+                    if (cdev->is_inserting || cdev->is_removing ||
+                        cdev->fw_remove) {
                         cpu_st->selector = iter;
                         trace_cpuhp_acpi_cpu_has_events(cpu_st->selector,
                             cdev->is_inserting, cdev->is_removing);

hw/acpi/trace-events

@@ -29,6 +29,8 @@ cpuhp_acpi_clear_inserting_evt(uint32_t idx) "idx[0x%"PRIx32"]"
 cpuhp_acpi_clear_remove_evt(uint32_t idx) "idx[0x%"PRIx32"]"
 cpuhp_acpi_ejecting_invalid_cpu(uint32_t idx) "0x%"PRIx32
 cpuhp_acpi_ejecting_cpu(uint32_t idx) "0x%"PRIx32
+cpuhp_acpi_fw_remove_invalid_cpu(uint32_t idx) "0x%"PRIx32
+cpuhp_acpi_fw_remove_cpu(uint32_t idx) "0x%"PRIx32
 cpuhp_acpi_write_ost_ev(uint32_t slot, uint32_t ev) "idx[0x%"PRIx32"] OST EVENT: 0x%"PRIx32
 cpuhp_acpi_write_ost_status(uint32_t slot, uint32_t st) "idx[0x%"PRIx32"] OST STATUS: 0x%"PRIx32
 

include/hw/acpi/cpu.h

@@ -22,6 +22,7 @@ typedef struct AcpiCpuStatus {
     uint64_t arch_id;
     bool is_inserting;
     bool is_removing;
+    bool fw_remove;
     uint32_t ost_event;
     uint32_t ost_status;
 } AcpiCpuStatus;