docs/specs/acpi_nvdimm.txt - qemu - Git at Google

 QEMU<->ACPI BIOS NVDIMM interface
 ---------------------------------

 QEMU supports NVDIMM via ACPI. This document describes the basic concepts of
 NVDIMM ACPI and the interface between QEMU and the ACPI BIOS.

 NVDIMM ACPI Background
 ----------------------
 NVDIMM is introduced in ACPI 6.0 which defines an NVDIMM root device under
 _SB scope with a _HID of “ACPI0012”. For each NVDIMM present or intended
 to be supported by platform, platform firmware also exposes an ACPI
 Namespace Device under the root device.

 The NVDIMM child devices under the NVDIMM root device are defined with _ADR
 corresponding to the NFIT device handle. The NVDIMM root device and the
 NVDIMM devices can have device specific methods (_DSM) to provide additional
 functions specific to a particular NVDIMM implementation.

 This is an example from ACPI 6.0, a platform contains one NVDIMM:

 Scope (\_SB){
    Device (NVDR) // Root device
    {
       Name (_HID, “ACPI0012”)
       Method (_STA) {...}
       Method (_FIT) {...}
       Method (_DSM, ...) {...}
       Device (NVD)
       {
          Name(_ADR, h) //where h is NFIT Device Handle for this NVDIMM
          Method (_DSM, ...) {...}
       }
    }
 }

 Method supported on both NVDIMM root device and NVDIMM device
 _DSM (Device Specific Method)
    It is a control method that enables devices to provide device specific
    control functions that are consumed by the device driver.
    The NVDIMM DSM specification can be found at:
         http://pmem.io/documents/NVDIMM_DSM_Interface_Example.pdf

    Arguments:
    Arg0 – A Buffer containing a UUID (16 Bytes)
    Arg1 – An Integer containing the Revision ID (4 Bytes)
    Arg2 – An Integer containing the Function Index (4 Bytes)
    Arg3 – A package containing parameters for the function specified by the
           UUID, Revision ID, and Function Index

    Return Value:
    If Function Index = 0, a Buffer containing a function index bitfield.
    Otherwise, the return value and type depends on the UUID, revision ID
    and function index which are described in the DSM specification.

 Methods on NVDIMM ROOT Device
 _FIT(Firmware Interface Table)
    It evaluates to a buffer returning data in the format of a series of NFIT
    Type Structure.

    Arguments: None

    Return Value:
    A Buffer containing a list of NFIT Type structure entries.

    The detailed definition of the structure can be found at ACPI 6.0: 5.2.25
    NVDIMM Firmware Interface Table (NFIT).

 QEMU NVDIMM Implementation
 ==========================
 QEMU uses 4 bytes IO Port starting from 0x0a18 and a RAM-based memory page
 for NVDIMM ACPI.

 Memory:
    QEMU uses BIOS Linker/loader feature to ask BIOS to allocate a memory
    page and dynamically patch its into a int32 object named "MEMA" in ACPI.

    This page is RAM-based and it is used to transfer data between _DSM
    method and QEMU. If ACPI has control, this pages is owned by ACPI which
    writes _DSM input data to it, otherwise, it is owned by QEMU which
    emulates _DSM access and writes the output data to it.

    ACPI writes _DSM Input Data (based on the offset in the page):
    [0x0 - 0x3]: 4 bytes, NVDIMM Device Handle.

                 The handle is completely QEMU internal thing, the values in
                 range [1, 0xFFFF] indicate nvdimm device. Other values are
                 reserved for other purposes.

                 Reserved handles:
                 0 is reserved for nvdimm root device named NVDR.
                 0x10000 is reserved for QEMU internal DSM function called on
                 the root device.

    [0x4 - 0x7]: 4 bytes, Revision ID, that is the Arg1 of _DSM method.
    [0x8 - 0xB]: 4 bytes. Function Index, that is the Arg2 of _DSM method.
    [0xC - 0xFFF]: 4084 bytes, the Arg3 of _DSM method.

    QEMU Writes Output Data (based on the offset in the page):
    [0x0 - 0x3]: 4 bytes, the length of result
    [0x4 - 0xFFF]: 4092 bytes, the DSM result filled by QEMU

 IO Port 0x0a18 - 0xa1b:
    ACPI writes the address of the memory page allocated by BIOS to this
    port then QEMU gets the control and fills the result in the memory page.

    write Access:
    [0x0a18 - 0xa1b]: 4 bytes, the address of the memory page allocated
                      by BIOS.

 _DSM process diagram:
 ---------------------
 "MEMA" indicates the address of memory page allocated by BIOS.

  +----------------------+      +-----------------------+
  |    1. OSPM           |      |    2. OSPM            |
  | save _DSM input data |      |  write "MEMA" to      | Exit to QEMU
  | to the page          +----->|  IO port 0x0a18       +------------+
  | indicated by "MEMA"  |      |                       |            |
  +----------------------+      +-----------------------+            |
                                                                     |
                                                                     v
  +-------------   ----+       +-----------+      +------------------+--------+
  |      5 QEMU        |       | 4 QEMU    |      |        3. QEMU            |
  | write _DSM result  |       |  emulate  |      | get _DSM input data from  |
  | to the page        +<------+ _DSM      +<-----+ the page indicated by the |
  |                    |       |           |      | value from the IO port    |
  +--------+-----------+       +-----------+      +---------------------------+
           |
           | Enter Guest
           |
           v
  +--------------------------+      +--------------+
  |     6 OSPM               |      |   7 OSPM     |
  | result size is returned  |      |  _DSM return |
  | by reading  DSM          +----->+              |
  | result from the page     |      |              |
  +--------------------------+      +--------------+

 NVDIMM hotplug
 --------------
 ACPI BIOS GPE.4 handler is dedicated for notifying OS about nvdimm device
 hot-add event.

 QEMU internal use only _DSM function
 ------------------------------------
 1) Read FIT
    _FIT method uses _DSM method to fetch NFIT structures blob from QEMU
    in 1 page sized increments which are then concatenated and returned
    as _FIT method result.

    Input parameters:
    Arg0 – UUID {set to 648B9CF2-CDA1-4312-8AD9-49C4AF32BD62}
    Arg1 – Revision ID (set to 1)
    Arg2 - Function Index, 0x1
    Arg3 - A package containing a buffer whose layout is as follows:

    +----------+--------+--------+-------------------------------------------+
    |  Field   | Length | Offset |                 Description               |
    +----------+--------+--------+-------------------------------------------+
    | offset   |   4    |   0    | offset in QEMU's NFIT structures blob to  |
    |          |        |        | read from                                 |
    +----------+--------+--------+-------------------------------------------+

    Output layout in the dsm memory page:
    +----------+--------+--------+-------------------------------------------+
    |  Field   | Length | Offset |                 Description               |
    +----------+--------+--------+-------------------------------------------+
    | length   |   4    |   0    | length of entire returned data            |
    |          |        |        | (including this header)                   |
    +----------+-----------------+-------------------------------------------+
    |          |        |        | return status codes                       |
    |          |        |        | 0x0 - success                             |
    |          |        |        | 0x100 - error caused by NFIT update while |
    | status   |   4    |   4    | read by _FIT wasn't completed, other      |
    |          |        |        | codes follow Chapter 3 in DSM Spec Rev1   |
    +----------+-----------------+-------------------------------------------+
    | fit data | Varies |   8    | contains FIT data, this field is present  |
    |          |        |        | if status field is 0;                     |
    +----------+--------+--------+-------------------------------------------+

    The FIT offset is maintained by the OSPM itself, current offset plus
    the size of the fit data returned by the function is the next offset
    OSPM should read. When all FIT data has been read out, zero fit data
    size is returned.

    If it returns status code 0x100, OSPM should restart to read FIT (read
    from offset 0 again).
	QEMU<->ACPI BIOS NVDIMM interface
	---------------------------------

	QEMU supports NVDIMM via ACPI. This document describes the basic concepts of
	NVDIMM ACPI and the interface between QEMU and the ACPI BIOS.

	NVDIMM ACPI Background
	----------------------
	NVDIMM is introduced in ACPI 6.0 which defines an NVDIMM root device under
	_SB scope with a _HID of “ACPI0012”. For each NVDIMM present or intended
	to be supported by platform, platform firmware also exposes an ACPI
	Namespace Device under the root device.

	The NVDIMM child devices under the NVDIMM root device are defined with _ADR
	corresponding to the NFIT device handle. The NVDIMM root device and the
	NVDIMM devices can have device specific methods (_DSM) to provide additional
	functions specific to a particular NVDIMM implementation.

	This is an example from ACPI 6.0, a platform contains one NVDIMM:

	Scope (\_SB){
	Device (NVDR) // Root device
	{
	Name (_HID, “ACPI0012”)
	Method (_STA) {...}
	Method (_FIT) {...}
	Method (_DSM, ...) {...}
	Device (NVD)
	{
	Name(_ADR, h) //where h is NFIT Device Handle for this NVDIMM
	Method (_DSM, ...) {...}
	}
	}
	}

	Method supported on both NVDIMM root device and NVDIMM device
	_DSM (Device Specific Method)
	It is a control method that enables devices to provide device specific
	control functions that are consumed by the device driver.
	The NVDIMM DSM specification can be found at:
	http://pmem.io/documents/NVDIMM_DSM_Interface_Example.pdf

	Arguments:
	Arg0 – A Buffer containing a UUID (16 Bytes)
	Arg1 – An Integer containing the Revision ID (4 Bytes)
	Arg2 – An Integer containing the Function Index (4 Bytes)
	Arg3 – A package containing parameters for the function specified by the
	UUID, Revision ID, and Function Index

	Return Value:
	If Function Index = 0, a Buffer containing a function index bitfield.
	Otherwise, the return value and type depends on the UUID, revision ID
	and function index which are described in the DSM specification.

	Methods on NVDIMM ROOT Device
	_FIT(Firmware Interface Table)
	It evaluates to a buffer returning data in the format of a series of NFIT
	Type Structure.

	Arguments: None

	Return Value:
	A Buffer containing a list of NFIT Type structure entries.

	The detailed definition of the structure can be found at ACPI 6.0: 5.2.25
	NVDIMM Firmware Interface Table (NFIT).

	QEMU NVDIMM Implementation
	==========================
	QEMU uses 4 bytes IO Port starting from 0x0a18 and a RAM-based memory page
	for NVDIMM ACPI.

	Memory:
	QEMU uses BIOS Linker/loader feature to ask BIOS to allocate a memory
	page and dynamically patch its into a int32 object named "MEMA" in ACPI.

	This page is RAM-based and it is used to transfer data between _DSM
	method and QEMU. If ACPI has control, this pages is owned by ACPI which
	writes _DSM input data to it, otherwise, it is owned by QEMU which
	emulates _DSM access and writes the output data to it.

	ACPI writes _DSM Input Data (based on the offset in the page):
	[0x0 - 0x3]: 4 bytes, NVDIMM Device Handle.

	The handle is completely QEMU internal thing, the values in
	range [1, 0xFFFF] indicate nvdimm device. Other values are
	reserved for other purposes.

	Reserved handles:
	0 is reserved for nvdimm root device named NVDR.
	0x10000 is reserved for QEMU internal DSM function called on
	the root device.

	[0x4 - 0x7]: 4 bytes, Revision ID, that is the Arg1 of _DSM method.
	[0x8 - 0xB]: 4 bytes. Function Index, that is the Arg2 of _DSM method.
	[0xC - 0xFFF]: 4084 bytes, the Arg3 of _DSM method.

	QEMU Writes Output Data (based on the offset in the page):
	[0x0 - 0x3]: 4 bytes, the length of result
	[0x4 - 0xFFF]: 4092 bytes, the DSM result filled by QEMU

	IO Port 0x0a18 - 0xa1b:
	ACPI writes the address of the memory page allocated by BIOS to this
	port then QEMU gets the control and fills the result in the memory page.

	write Access:
	[0x0a18 - 0xa1b]: 4 bytes, the address of the memory page allocated
	by BIOS.

	_DSM process diagram:
	---------------------
	"MEMA" indicates the address of memory page allocated by BIOS.

	+----------------------+ +-----------------------+
	\| 1. OSPM \| \| 2. OSPM \|
	\| save _DSM input data \| \| write "MEMA" to \| Exit to QEMU
	\| to the page +----->\| IO port 0x0a18 +------------+
	\| indicated by "MEMA" \| \| \| \|
	+----------------------+ +-----------------------+ \|
	\|
	v
	+------------- ----+ +-----------+ +------------------+--------+
	\| 5 QEMU \| \| 4 QEMU \| \| 3. QEMU \|
	\| write _DSM result \| \| emulate \| \| get _DSM input data from \|
	\| to the page +<------+ _DSM +<-----+ the page indicated by the \|
	\| \| \| \| \| value from the IO port \|
	+--------+-----------+ +-----------+ +---------------------------+
	\|
	\| Enter Guest
	\|
	v
	+--------------------------+ +--------------+
	\| 6 OSPM \| \| 7 OSPM \|
	\| result size is returned \| \| _DSM return \|
	\| by reading DSM +----->+ \|
	\| result from the page \| \| \|
	+--------------------------+ +--------------+

	NVDIMM hotplug
	--------------
	ACPI BIOS GPE.4 handler is dedicated for notifying OS about nvdimm device
	hot-add event.

	QEMU internal use only _DSM function
	------------------------------------
	1) Read FIT
	_FIT method uses _DSM method to fetch NFIT structures blob from QEMU
	in 1 page sized increments which are then concatenated and returned
	as _FIT method result.

	Input parameters:
	Arg0 – UUID {set to 648B9CF2-CDA1-4312-8AD9-49C4AF32BD62}
	Arg1 – Revision ID (set to 1)
	Arg2 - Function Index, 0x1
	Arg3 - A package containing a buffer whose layout is as follows:

	+----------+--------+--------+-------------------------------------------+
	\| Field \| Length \| Offset \| Description \|
	+----------+--------+--------+-------------------------------------------+
	\| offset \| 4 \| 0 \| offset in QEMU's NFIT structures blob to \|
	\| \| \| \| read from \|
	+----------+--------+--------+-------------------------------------------+

	Output layout in the dsm memory page:
	+----------+--------+--------+-------------------------------------------+
	\| Field \| Length \| Offset \| Description \|
	+----------+--------+--------+-------------------------------------------+
	\| length \| 4 \| 0 \| length of entire returned data \|
	\| \| \| \| (including this header) \|
	+----------+-----------------+-------------------------------------------+
	\| \| \| \| return status codes \|
	\| \| \| \| 0x0 - success \|
	\| \| \| \| 0x100 - error caused by NFIT update while \|
	\| status \| 4 \| 4 \| read by _FIT wasn't completed, other \|
	\| \| \| \| codes follow Chapter 3 in DSM Spec Rev1 \|
	+----------+-----------------+-------------------------------------------+
	\| fit data \| Varies \| 8 \| contains FIT data, this field is present \|
	\| \| \| \| if status field is 0; \|
	+----------+--------+--------+-------------------------------------------+

	The FIT offset is maintained by the OSPM itself, current offset plus
	the size of the fit data returned by the function is the next offset
	OSPM should read. When all FIT data has been read out, zero fit data
	size is returned.

	If it returns status code 0x100, OSPM should restart to read FIT (read
	from offset 0 again).