Re: [Qemu-devel] [RFC PATCH v2 00/21] ACPI memory hotplug

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On Thu, Jul 12, 2012 at 08:04:56PM +0000, Blue Swirl wrote:
> On Wed, Jul 11, 2012 at 10:31 AM, Vasilis Liaskovitis
> <vasilis.liaskovitis@xxxxxxxxxxxxxxxx> wrote:
> > This is v2 of the ACPI memory hotplug prototype for x86_64 target.
> 
> I think the concept of DIMMs (what about SIMMs? SODIMMs? I liked
> memslot) would be useful for most targets, but hotplugging may be
> limited to x86 only. It would be nice to keep these two separate or as
> loosely coupled as possible.

agreed.
what specific usecases besides hotplugging are you thinking about? 
Also are there non-acpi hotplug platforms?

I am trying to keep generic dimm manipulation functions (e.g. population /
depopulation and searching) in hw/dimm[.ch]. Currently the x86-acpi_piix4 "backend"
registers a callback for hot-add / hot-remove. In theory other hotplug backends
can hook in. 

btw I don't mind using "-memslot" (I think someone during v1 mentioned -dimm), we just
need some consensus on the naming.

> 
> >
> > Changes v1->v2
> >
> > - memory map is automatically calculated for hotplug dimms. Dimms are added from
> > top-of-memory skipping the pci hole at [PCI_HOLE_START, 4G).
> > - Renamed from "-memslot" to "-dimm". Commands changed to "dimm_add", "dimm_del".
> > - Seabios ejection array reduced to a byte. Use extraction macros for dimm ssdt.
> > - additional SRAT paravirt info does not break previous SRAT fw_cfg layout.
> > - Documentation of new acpi_piix4 registers and paravirt data.
> > - add ACPI _OST support for _OST enabled guests. This allows qemu to receive
> > notification for success / failure of memory hot-add and hot-remove operations.
> > Guest needs to support _OST (https://lkml.org/lkml/2012/6/25/321)
> > - add monitor info command to report total guest memory (initial + hot-added)
> > - add command line options and monitor commands for batch dimm creation/population
> >
> > Overview:
> >
> > Dimm devices are modeled with a new qemu command line
> >
> > "-dimm id=name,size=sz,node=pxm,populated=on|off"
> >
> > As already mentioned, the starting physical address for all dimms is calculated
> > automatically from top of memory, skipping the pci hole at [PCI_HOLE_START, 4G).
> > Node is defining numa proximity for this dimm. When not defined it defaults
> > to zero.
> > "-dimm id=dimm0,size=512M,node=0,populated=off"
> > will define a 512M memory slot belonging to numa node 0.
> >
> > Dimms are added or removed with a new hmp command "dimm_add/dimm_del":
> > Hot-add syntax: "dimm_add id"
> > Hot-remove syntax: "dimm_del id"
> >
> > Issues:
> >
> > - Live migration works as long as populated field is changed to "on" for
> > hotplugged dimms at the destination qemu command line (patch 12/21 lifts
> > this requirement). The DimmState structure does not yet define a
> > VMStateDescription, but i assume this is the preferred way to pass state
> > for migration.
> >
> > - Dimms are abstracted as qdevices attached to the main system bus. However,
> > memory hotplugging has its own side channel ignoring main_system_bus's hotplug
> > incapability. A cleaner integration is still needed, probably attaching memory
> > devices as children-links of an acpi-capable device (in the pc case acpi_piix4)
> > instead of the system bus (TBD). Then device_add/device_del instead of new
> > commands can hopefully be used.
> >
> > Comments/review welcome.
> >
> > series is based on uq/master for qemu-kvm, and master for seabios. Can be found
> > also at:
> > http://github.com/vliaskov/qemu-kvm/commits/memhp-v2
> > http://github.com/vliaskov/seabios/commits/memhp-v2
> >
> > Vasilis Liaskovitis (14):
> >   dimm: Implement memory device abstraction
> >   acpi_piix4: Implement memory device hotplug registers
> >   pc: calculate dimm physical addresses and adjust memory map
> >   pc: Add dimm paravirt SRAT info
> >   Implement "-dimm" command line option
> >   Implement dimm_add and dimm_del commands for hmp and qmp
> >   fix live-migration when "populated=on" is missing
> >   Implement memory hotplug notification lists
> >   acpi_piix4: _OST dimm support
> >   acpi_piix4: Update dimm state on VM reboot
> >   acpi_piix4: Update dimm bitmap state on hot-remove fail
> >   Implement "info memtotal" and "query-memtotal"
> >   Implement -dimms, -dimmspop command line options
> >   Implement mem_increase, mem_decrease hmp/qmp commands
> >
> >  arch_init.c                 |   23 ++-
> >  docs/specs/acpi_hotplug.txt |   46 +++++
> >  docs/specs/fwcfg.txt        |   28 +++
> >  hmp-commands.hx             |   67 +++++++
> >  hmp.c                       |   24 +++
> >  hmp.h                       |    2 +
> >  hw/Makefile.objs            |    2 +-
> >  hw/acpi_piix4.c             |  131 ++++++++++++-
> >  hw/dimm.c                   |  449 +++++++++++++++++++++++++++++++++++++++++++
> >  hw/dimm.h                   |   72 +++++++
> >  hw/pc.c                     |   94 +++++++++-
> >  hw/pc.h                     |    6 +
> >  hw/pc_piix.c                |   18 ++-
> >  monitor.c                   |   35 ++++
> >  monitor.h                   |    5 +
> >  qapi-schema.json            |   38 ++++
> >  qemu-config.c               |   70 +++++++
> >  qemu-options.hx             |   15 ++
> >  qmp-commands.hx             |  137 +++++++++++++
> >  sysemu.h                    |    1 +
> >  vl.c                        |  122 ++++++++++++-
> >  21 files changed, 1368 insertions(+), 17 deletions(-)
> >  create mode 100644 docs/specs/acpi_hotplug.txt
> >  create mode 100644 docs/specs/fwcfg.txt
> >  create mode 100644 hw/dimm.c
> >  create mode 100644 hw/dimm.h
> >
> > Vasilis Liaskovitis (7):
> >   Add ACPI_EXTRACT_DEVICE* macros
> >   Add SSDT memory device support
> >   acpi-dsdt: Implement functions for memory hotplug.
> >   acpi: generate hotplug memory devices.
> >   pciinit: Fix pcimem_start value
> >   acpi_dsdt: Support _OST dimm method
> >   acpi_dsdt: Revert internal dimm state on _OST failure
> >
> >  Makefile              |    2 +-
> >  src/acpi-dsdt.dsl     |  120 ++++++++++++++++++++++++++++++++++++-
> >  src/acpi.c            |  158 +++++++++++++++++++++++++++++++++++++++++++++++--
> >  src/pciinit.c         |    2 +-
> >  src/ssdt-mem.dsl      |   69 +++++++++++++++++++++
> >  tools/acpi_extract.py |   28 +++++++++
> >  6 files changed, 369 insertions(+), 10 deletions(-)
> >  create mode 100644 src/ssdt-mem.dsl
> >
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