| QEMU<->ACPI BIOS memory hotplug interface |
| -------------------------------------- |
| |
| ACPI BIOS GPE.3 handler is dedicated for notifying OS about memory hot-add |
| and hot-remove events. |
| |
| Memory hot-plug interface (IO port 0xa00-0xa17, 1-4 byte access): |
| --------------------------------------------------------------- |
| 0xa00: |
| read access: |
| [0x0-0x3] Lo part of memory device phys address |
| [0x4-0x7] Hi part of memory device phys address |
| [0x8-0xb] Lo part of memory device size in bytes |
| [0xc-0xf] Hi part of memory device size in bytes |
| [0x10-0x13] Memory device proximity domain |
| [0x14] Memory device status fields |
| bits: |
| 0: Device is enabled and may be used by guest |
| 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: 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: |
| [0x0-0x3] Memory device slot selector, selects active memory device. |
| All following accesses to other registers in 0xa00-0xa17 |
| region will read/store data from/to selected memory device. |
| [0x4-0x7] OST event code reported by OSPM |
| [0x8-0xb] OST status code reported by OSPM |
| [0xc-0x13] reserved, writes into it are ignored |
| [0x14] Memory device control fields |
| bits: |
| 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: 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 | |
| +------------------+ | | |
| +-------------------+ |
