It describes the basic concepts of NVDIMM ACPI and the interface between QEMU and the ACPI BIOS
Signed-off-by: Xiao Guangrong <guangrong.x...@linux.intel.com> --- docs/specs/acpi_nvdimm.txt | 179 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 179 insertions(+) create mode 100644 docs/specs/acpi_nvdimm.txt diff --git a/docs/specs/acpi_nvdimm.txt b/docs/specs/acpi_nvdimm.txt new file mode 100644 index 0000000..cc5db2c --- /dev/null +++ b/docs/specs/acpi_nvdimm.txt @@ -0,0 +1,179 @@ +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, ...) {...} + } + } +} + +Methods supported on both NVDIMM root device and NVDIMM device are +1) _STA(Status) + It returns the current status of a device, which can be one of the + following: enabled, disabled, or removed. + + Arguments: None + + Return Value: + It returns an An Integer which is defined as followings: + Bit [0] – Set if the device is present. + Bit [1] – Set if the device is enabled and decoding its resources. + Bit [2] – Set if the device should be shown in the UI. + Bit [3] – Set if the device is functioning properly (cleared if device + failed its diagnostics). + Bit [4] – Set if the battery is present. + Bits [31:5] – Reserved (must be cleared). + +2) _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 Implemention +======================== +QEMU reserves a page starting from 0xFF00000 and 4 bytes IO Port starting +from 0x0a18 for NVDIMM ACPI. + +Memory 0xFF00000 - 0xFF00FFF: + 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: + [0xFF00000 - 0xFF00003]: 4 bytes, NVDIMM Devcie Handle, 0 is reserved + for NVDIMM Root device. + [0xFF00004 - 0xFF00007]: 4 bytes, Revision ID, that is the Arg1 of _DSM + method. + [0xFF00008 - 0xFF0000B]: 4 bytes. Function Index, that is the Arg2 of + _DSM method. + [0xFF0000C - 0xFF00FFF]: 4084 bytes, the Arg3 of _DSM method + + QEMU Writes Output Data: + [0xFF00000 - 0xFF00FFF]: the DSM return result filled by QEMU + +IO Port 0x0a18 - 0xa1b: + ACPI uses it to transfer control from guest to QEMU and read the size + of return result filled by QEMU + + Read Access: + [0x0a18 - 0xa1b]: 4 bytes, the buffer size of _DSM output data. + +_DSM process diagram: +--------------------- +The page, 0xFF00000 - 0xFF00FFF, is used by _DSM Virtualization. + + +----------------------+ +-----------------------+ + | 1. OSPM | | 2. OSPM | + | save _DSM input data | | read 0x0a18 | Exit to QEMU + | to the page +----->| +------------+ + | | | | | + +----------------------+ +-----------------------+ | + | + v + +------------- ----+ +-----------+ +------------------+--------+ + | 5 QEMU | | 4 QEMU | | 3. QEMU | + | write _DSM result | | emulate | | get _DSM input parameters | + | to the page +<------+ _DSM +<-----+ from the page | + | | | | | | + +--------+-----------+ +-----------+ +---------------------------+ + | + | Enter Guest + | + v + +--------------------------+ +--------------+ + | 6 OSPM | | 7 OSPM | + | result size is returned | | _DSM return | + | by read and get DSM +----->+ | + | result from the page | | | + +--------------------------+ +--------------+ + + QEMU internal use only _DSM function + ------------------------------------ + There is the function introduced by QEMU and only used by QEMU internal. + + 1) Read FIT + As we only reserved one page for NVDIMM ACPI it is impossible to map the + whole FIT data to guest's address space. This function is used by _FIT + method to read a piece of FIT data from QEMU. + + Input parameters: + Arg0 – UUID {set to 2f10e7a4-9e91-11e4-89d3-123b93f75cba} + Arg1 – Revision ID (set to 1) + Arg2 - 0xFFFFFFFF + Arg3 - A package containing a buffer whose layout is as follows: + + +----------+-------------+-------------+-----------------------------------+ + | Filed | Byte Length | Byte Offset | Description | + +----------+-------------+-------------+-----------------------------------+ + | offset | 4 | 0 | the offset of FIT buffer | + +----------+-------------+-------------+-----------------------------------+ + + Output: + +----------+-------------+-------------+-----------------------------------+ + | Filed | Byte Length | Byte Offset | Description | + +----------+-------------+-------------+-----------------------------------+ + | status | 4 | 0 | return status codes following | + | | | | Chapter 3 in DSM Spec Rev1 | + +----------+-------------+-------------+-----------------------------------+ + | length | 4 | 4 | the length of FIT buffer read out | + +----------+-------------+-------------+-----------------------------------+ + | fit data | Varies | 8 | FIT data, its size is indicated | + | | | | by length field above | + +----------+-------------+-------------+-----------------------------------+ + + The FIT offset is maintained by the caller itself, current offset plugs + the length returned by the function is the next offset we should read. + When all the FIT data has been read out, zero length is returned. -- 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html