Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging

[qemu.git] / docs / specs / acpi_mem_hotplug.txt

diff --git a/docs/specs/acpi_mem_hotplug.txt b/docs/specs/acpi_mem_hotplug.txt
index 12909940ccded731e96b283d8fb5a65c40eb7be4..3df3620ce42a45db7061acaa8c1b7f4998feaae3 100644 (file)
--- a/docs/specs/acpi_mem_hotplug.txt
+++ b/docs/specs/acpi_mem_hotplug.txt
@@ -2,7 +2,7 @@ QEMU<->ACPI BIOS memory hotplug interface
 --------------------------------------
 
 ACPI BIOS GPE.3 handler is dedicated for notifying OS about memory hot-add
-events.
+and hot-remove events.
 
 Memory hot-plug interface (IO port 0xa00-0xa17, 1-4 byte access):
 ---------------------------------------------------------------
@@ -19,7 +19,9 @@ Memory hot-plug interface (IO port 0xa00-0xa17, 1-4 byte access):
               1: Device insert event, used to distinguish device for which
                  no device check event to OSPM was issued.
                  It's valid only when bit 1 is set.
-              2-7: reserved and should be ignored by OSPM
+              2: Device remove event, used to distinguish device for which
+                 no device eject request to OSPM was issued.
+              3-7: reserved and should be ignored by OSPM
       [0x15-0x17] reserved
 
   write access:
@@ -31,14 +33,62 @@ Memory hot-plug interface (IO port 0xa00-0xa17, 1-4 byte access):
       [0xc-0x13] reserved, writes into it are ignored
       [0x14] Memory device control fields
           bits:
-              0: reserved, OSPM must clear it before writing to register
+              0: reserved, OSPM must clear it before writing to register.
+                 Due to BUG in versions prior 2.4 that field isn't cleared
+                 when other fields are written. Keep it reserved and don't
+                 try to reuse it.
               1: if set to 1 clears device insert event, set by OSPM
                  after it has emitted device check event for the
                  selected memory device
-              2-7: reserved, OSPM must clear them before writing to register
+              2: if set to 1 clears device remove event, set by OSPM
+                 after it has emitted device eject request for the
+                 selected memory device
+              3: if set to 1 initiates device eject, set by OSPM when it
+                 triggers memory device removal and calls _EJ0 method
+              4-7: reserved, OSPM must clear them before writing to register
 
 Selecting memory device slot beyond present range has no effect on platform:
    - write accesses to memory hot-plug registers not documented above are
      ignored
    - read accesses to memory hot-plug registers not documented above return
      all bits set to 1.
+
+Memory hot remove process diagram:
+----------------------------------
+ +-------------+     +-----------------------+      +------------------+     
+ |  1. QEMU    |     | 2. QEMU               |      |3. QEMU           |     
+ |  device_del +---->+ device unplug request +----->+Send SCI to guest,|     
+ |             |     |         cb            |      |return control to |     
+ +-------------+     +-----------------------+      |management        |     
+                                                    +------------------+     
+                                                                             
+ +---------------------------------------------------------------------+     
+                                                                             
+ +---------------------+              +-------------------------+            
+ | OSPM:               | remove event | OSPM:                   |            
+ | send Eject Request, |              | Scan memory devices     |            
+ | clear remove event  +<-------------+ for event flags         |            
+ |                     |              |                         |            
+ +---------------------+              +-------------------------+            
+           |                                                                 
+           |                                                                 
+ +---------v--------+            +-----------------------+                   
+ | Guest OS:        |  success   | OSPM:                 |                   
+ | process Ejection +----------->+ Execute _EJ0 method,  |                   
+ | request          |            | set eject bit in flags|                   
+ +------------------+            +-----------------------+                   
+           |failure                         |                                
+           v                                v                                
+ +------------------------+      +-----------------------+                   
+ | OSPM:                  |      | QEMU:                 |                   
+ | set OST event & status |      | call device unplug cb |                   
+ | fields                 |      |                       |                   
+ +------------------------+      +-----------------------+                   
+          |                                  |                               
+          v                                  v                               
+ +------------------+              +-------------------+                     
+ |QEMU:             |              |QEMU:              |                     
+ |Send OST QMP event|              |Send device deleted|                     
+ |                  |              |QMP event          |                     
+ +------------------+              |                   |                     
+                                   +-------------------+