diff options
Diffstat (limited to 'docs/specs/acpi_mem_hotplug.txt')
| -rw-r--r-- | docs/specs/acpi_mem_hotplug.txt | 58 |
1 files changed, 54 insertions, 4 deletions
diff --git a/docs/specs/acpi_mem_hotplug.txt b/docs/specs/acpi_mem_hotplug.txt index 12909940c..3df3620ce 100644 --- 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 | + +------------------+ | | + +-------------------+ |