diff options
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/memory-hotplug.txt | 23 | ||||
| -rw-r--r-- | docs/specs/acpi_mem_hotplug.txt | 42 |
2 files changed, 61 insertions, 4 deletions
diff --git a/docs/memory-hotplug.txt b/docs/memory-hotplug.txt index f70571df0c..56bdd0a47b 100644 --- a/docs/memory-hotplug.txt +++ b/docs/memory-hotplug.txt @@ -4,9 +4,7 @@ QEMU memory hotplug This document explains how to use the memory hotplug feature in QEMU, which is present since v2.1.0. -Please, note that memory hotunplug is not supported yet. This means -that you're able to add memory, but you're not able to remove it. -Also, proper guest support is required for memory hotplug to work. +Guest support is required for memory hotplug to work. Basic RAM hotplug ----------------- @@ -74,3 +72,22 @@ comes from regular RAM, 1GB is a 1GB hugepage page and 256MB is from -device pc-dimm,id=dimm1,memdev=mem1 \ -object memory-backend-file,id=mem2,size=256M,mem-path=/mnt/hugepages-2MB \ -device pc-dimm,id=dimm2,memdev=mem2 + + +RAM hot-unplug +--------------- + +In order to be able to hot unplug pc-dimm device, QEMU has to be told the ids +of pc-dimm device and memory backend object. The ids were assigned when you hot +plugged memory. + +Two monitor commands are used to hot unplug memory: + + - "device_del": deletes a front-end pc-dimm device + - "object_del": deletes a memory backend object + +For example, assuming that the pc-dimm device with id "dimm1" exists, and its memory +backend is "mem1", the following commands tries to remove it. + + (qemu) device_del dimm1 + (qemu) object_del mem1 diff --git a/docs/specs/acpi_mem_hotplug.txt b/docs/specs/acpi_mem_hotplug.txt index 12909940cc..dcc4808918 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): --------------------------------------------------------------- @@ -42,3 +42,43 @@ Selecting memory device slot beyond present range has no effect on platform: 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 | + +------------------+ | | + +-------------------+ |