From 894cf84bf9f723f93e056deae4c5a54c96b15303 Mon Sep 17 00:00:00 2001 From: Igor Mammedov Date: Mon, 8 Jun 2015 00:51:59 +0200 Subject: [PATCH 01/44] docs: update documentation for memory hot unplug Message-id: <1433724727-46928-2-git-send-email-imammedo@redhat.com> Patchwork-id: 65388 O-Subject: [RHEL-7.2 qemu-kvm-rhev PATCH 1/9] docs: update documentation for memory hot unplug Bugzilla: 1120706 RH-Acked-by: Michael S. Tsirkin RH-Acked-by: Andrew Jones RH-Acked-by: Laszlo Ersek From: Zhu Guihua Add specification about how to use memory hot unplug, and add a flow diagram to explain memory hot unplug process. Reviewed-by: Igor Mammedov Signed-off-by: Zhu Guihua Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin (cherry picked from commit 4fccb4834d0455519ff6d7a81551a8dfd360fefa) Signed-off-by: Miroslav Rezanina --- docs/memory-hotplug.txt | 23 +++++++++++++++++++--- 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 f70571d..56bdd0a 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 1290994..dcc4808 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          |                      + +------------------+              |                   |                      +                                   +-------------------+ -- 1.8.3.1