diff mbox

[v5,4/5] nvdimm acpi: introduce _FIT method

Message ID 1478198186-45204-5-git-send-email-guangrong.xiao@linux.intel.com
State New, archived
Headers show

Commit Message

Xiao Guangrong Nov. 3, 2016, 6:36 p.m. UTC
_FIT is required for hotplug support, guest will inquire the
updated device info from it if a hotplug event is received

As FIT buffer is not completely mapped into guest address space,
Read_FIT method is introduced to read NFIT structures blob from
QEMU, The buffer is concatenated before _FIT return

Refer to docs/specs/acpi-nvdimm.txt for detailed design

Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
---
 docs/specs/acpi_nvdimm.txt |  61 ++++++++++++--
 hw/acpi/nvdimm.c           | 198 ++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 252 insertions(+), 7 deletions(-)

Comments

Igor Mammedov Nov. 4, 2016, 10:24 a.m. UTC | #1
On Fri,  4 Nov 2016 02:36:25 +0800
Xiao Guangrong <guangrong.xiao@linux.intel.com> wrote:

> _FIT is required for hotplug support, guest will inquire the
> updated device info from it if a hotplug event is received
> 
> As FIT buffer is not completely mapped into guest address space,
> Read_FIT method is introduced to read NFIT structures blob from
> QEMU, The buffer is concatenated before _FIT return
> 
> Refer to docs/specs/acpi-nvdimm.txt for detailed design
> 
> Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
> ---
>  docs/specs/acpi_nvdimm.txt |  61 ++++++++++++--
>  hw/acpi/nvdimm.c           | 198 ++++++++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 252 insertions(+), 7 deletions(-)
> 
> diff --git a/docs/specs/acpi_nvdimm.txt b/docs/specs/acpi_nvdimm.txt
> index 0fdd251..63cb63f 100644
> --- a/docs/specs/acpi_nvdimm.txt
> +++ b/docs/specs/acpi_nvdimm.txt
> @@ -65,8 +65,8 @@ _FIT(Firmware Interface Table)
>     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 NVDIMM Implementation
> +==========================
>  QEMU uses 4 bytes IO Port starting from 0x0a18 and a RAM-based memory page
>  for NVDIMM ACPI.
>  
> @@ -82,6 +82,16 @@ Memory:
>     ACPI writes _DSM Input Data (based on the offset in the page):
>     [0x0 - 0x3]: 4 bytes, NVDIMM Device Handle, 0 is reserved for NVDIMM
>                  Root device.
> +
> +                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.
> @@ -127,6 +137,47 @@ _DSM process diagram:
>   | result from the page     |      |              |
>   +--------------------------+      +--------------+
>  
> - _FIT implementation
> - -------------------
> - TODO (will fill it when nvdimm hotplug is introduced)
> +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 the header)                    |
s/the header/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 length is
> +   returned.
you mean here fit data length rather then what is in 'length' field,
you should talk here in terms of 'length' field.

> +
> +   If it returns status code 0x100, OSPM should restart to read FIT (read
> +   from offset 0 again).
> diff --git a/hw/acpi/nvdimm.c b/hw/acpi/nvdimm.c
> index d9d1ef7..f82ae4a 100644
> --- a/hw/acpi/nvdimm.c
> +++ b/hw/acpi/nvdimm.c
> @@ -478,6 +478,22 @@ typedef struct NvdimmFuncSetLabelDataIn NvdimmFuncSetLabelDataIn;
>  QEMU_BUILD_BUG_ON(sizeof(NvdimmFuncSetLabelDataIn) +
>                    offsetof(NvdimmDsmIn, arg3) > 4096);
>  
> +struct NvdimmFuncReadFITIn {
> +    uint32_t offset; /* the offset into FIT buffer. */
> +} QEMU_PACKED;
> +typedef struct NvdimmFuncReadFITIn NvdimmFuncReadFITIn;
> +QEMU_BUILD_BUG_ON(sizeof(NvdimmFuncReadFITIn) +
> +                  offsetof(NvdimmDsmIn, arg3) > 4096);
> +
> +struct NvdimmFuncReadFITOut {
> +    /* the size of buffer filled by QEMU. */
> +    uint32_t len;
> +    uint32_t func_ret_status; /* return status code. */
> +    uint8_t fit[0]; /* the FIT data. */
> +} QEMU_PACKED;
> +typedef struct NvdimmFuncReadFITOut NvdimmFuncReadFITOut;
> +QEMU_BUILD_BUG_ON(sizeof(NvdimmFuncReadFITOut) > 4096);
> +
>  static void
>  nvdimm_dsm_function0(uint32_t supported_func, hwaddr dsm_mem_addr)
>  {
> @@ -502,6 +518,73 @@ nvdimm_dsm_no_payload(uint32_t func_ret_status, hwaddr dsm_mem_addr)
>  #define NVDIMM_DSM_RET_STATUS_UNSUPPORT      1 /* Not Supported */
>  #define NVDIMM_DSM_RET_STATUS_NOMEMDEV       2 /* Non-Existing Memory Device */
>  #define NVDIMM_DSM_RET_STATUS_INVALID        3 /* Invalid Input Parameters */
> +#define NVDIMM_DSM_RET_STATUS_FIT_CHANGED    0x100 /* FIT Changed */
> +
> +#define NVDIMM_QEMU_RSVD_HANDLE_ROOT         0x10000
> +
> +/* Read FIT data, defined in docs/specs/acpi_nvdimm.txt. */
> +static void nvdimm_dsm_func_read_fit(AcpiNVDIMMState *state, NvdimmDsmIn *in,
> +                                     hwaddr dsm_mem_addr)
> +{
> +    NvdimmFitBuffer *fit_buf = &state->fit_buf;
> +    NvdimmFuncReadFITIn *read_fit;
> +    NvdimmFuncReadFITOut *read_fit_out;
> +    GArray *fit;
> +    uint32_t read_len = 0, func_ret_status, offset;
> +    int size;
> +
> +    read_fit = (NvdimmFuncReadFITIn *)in->arg3;
> +    offset = le32_to_cpu(read_fit->offset);
> +
> +    fit = fit_buf->fit;
> +
> +    nvdimm_debug("Read FIT: offset %#x FIT size %#x Dirty %s.\n",
> +                 offset, fit->len, fit_buf->dirty ? "Yes" : "No");
> +
> +    /* It is the first time to read FIT. */
> +    if (!offset) {
> +        fit_buf->dirty = false;
> +    } else if (fit_buf->dirty) { /* FIT has been changed during RFIT. */
> +        func_ret_status = NVDIMM_DSM_RET_STATUS_FIT_CHANGED;
> +        goto exit;
> +    }
> +
> +    if (offset > fit->len) {
> +        func_ret_status = NVDIMM_DSM_RET_STATUS_INVALID;
> +        goto exit;
> +    }
> +
> +    func_ret_status = NVDIMM_DSM_RET_STATUS_SUCCESS;
> +    read_len = MIN(fit->len - offset, 4096 - sizeof(NvdimmFuncReadFITOut));
                                         ^^^
should be macro that's used at place where page is allocated,
so that usage places won't go out of sync someday


> +
> +exit:
> +    size = sizeof(NvdimmFuncReadFITOut) + read_len;
> +    read_fit_out = g_malloc(size);
> +
> +    read_fit_out->len = cpu_to_le32(size);
> +    read_fit_out->func_ret_status = cpu_to_le32(func_ret_status);
> +    memcpy(read_fit_out->fit, fit->data + offset, read_len);
> +
> +    cpu_physical_memory_write(dsm_mem_addr, read_fit_out, size);
> +
> +    g_free(read_fit_out);
> +}
> +
> +static void
> +nvdimm_dsm_handle_reserved_root_method(AcpiNVDIMMState *state,
> +                                       NvdimmDsmIn *in, hwaddr dsm_mem_addr)
> +{
> +    switch (in->function) {
> +    case 0x0:
> +        nvdimm_dsm_function0(0x1 | 1 << 1 /* Read FIT */, dsm_mem_addr);
> +        return;
> +    case 0x1 /* Read FIT */:
> +        nvdimm_dsm_func_read_fit(state, in, dsm_mem_addr);
> +        return;
> +    }
> +
> +    nvdimm_dsm_no_payload(NVDIMM_DSM_RET_STATUS_UNSUPPORT, dsm_mem_addr);
> +}
>  
>  static void nvdimm_dsm_root(NvdimmDsmIn *in, hwaddr dsm_mem_addr)
>  {
> @@ -730,6 +813,7 @@ nvdimm_dsm_read(void *opaque, hwaddr addr, unsigned size)
>  static void
>  nvdimm_dsm_write(void *opaque, hwaddr addr, uint64_t val, unsigned size)
>  {
> +    AcpiNVDIMMState *state = opaque;
>      NvdimmDsmIn *in;
>      hwaddr dsm_mem_addr = val;
>  
> @@ -757,6 +841,11 @@ nvdimm_dsm_write(void *opaque, hwaddr addr, uint64_t val, unsigned size)
>          goto exit;
>      }
>  
> +    if (in->handle == NVDIMM_QEMU_RSVD_HANDLE_ROOT) {
> +        nvdimm_dsm_handle_reserved_root_method(state, in, dsm_mem_addr);
> +        goto exit;
> +     }
> +
>       /* Handle 0 is reserved for NVDIMM Root Device. */
>      if (!in->handle) {
>          nvdimm_dsm_root(in, dsm_mem_addr);
> @@ -809,9 +898,13 @@ void nvdimm_init_acpi_state(AcpiNVDIMMState *state, MemoryRegion *io,
>  #define NVDIMM_DSM_OUT_BUF_SIZE "RLEN"
>  #define NVDIMM_DSM_OUT_BUF      "ODAT"
>  
> +#define NVDIMM_DSM_RFIT_STATUS  "RSTA"
> +
> +#define NVDIMM_QEMU_RSVD_UUID   "648B9CF2-CDA1-4312-8AD9-49C4AF32BD62"
> +
>  static void nvdimm_build_common_dsm(Aml *dev)
>  {
> -    Aml *method, *ifctx, *function, *handle, *uuid, *dsm_mem;
> +    Aml *method, *ifctx, *function, *handle, *uuid, *dsm_mem, *elsectx2;
>      Aml *elsectx, *unsupport, *unpatched, *expected_uuid, *uuid_invalid;
>      Aml *pckg, *pckg_index, *pckg_buf, *field, *dsm_out_buf, *dsm_out_buf_size;
>      uint8_t byte_list[1];
> @@ -900,9 +993,15 @@ static void nvdimm_build_common_dsm(Aml *dev)
>                 /* UUID for NVDIMM Root Device */, expected_uuid));
>      aml_append(method, ifctx);
>      elsectx = aml_else();
> -    aml_append(elsectx, aml_store(
> +    ifctx = aml_if(aml_equal(handle, aml_int(NVDIMM_QEMU_RSVD_HANDLE_ROOT)));
> +    aml_append(ifctx, aml_store(aml_touuid(NVDIMM_QEMU_RSVD_UUID
> +               /* UUID for QEMU internal use */), expected_uuid));
> +    aml_append(elsectx, ifctx);
> +    elsectx2 = aml_else();
> +    aml_append(elsectx2, aml_store(
>                 aml_touuid("4309AC30-0D11-11E4-9191-0800200C9A66")
>                 /* UUID for NVDIMM Devices */, expected_uuid));
> +    aml_append(elsectx, elsectx2);
>      aml_append(method, elsectx);
>  
>      uuid_invalid = aml_lnot(aml_equal(uuid, expected_uuid));
> @@ -982,6 +1081,100 @@ static void nvdimm_build_device_dsm(Aml *dev, uint32_t handle)
>      aml_append(dev, method);
>  }
>  
> +static void nvdimm_build_fit_method(Aml *dev)
> +{
> +    Aml *method, *pkg, *buf, *buf_size, *offset, *call_result;
> +    Aml *whilectx, *ifcond, *ifctx, *elsectx, *fit;
> +
> +    buf = aml_local(0);
> +    buf_size = aml_local(1);
> +    fit = aml_local(2);
> +
> +    aml_append(dev, aml_name_decl(NVDIMM_DSM_RFIT_STATUS, aml_int(0)));
> +
> +    /* build helper function, RFIT. */
> +    method = aml_method("RFIT", 1, AML_SERIALIZED);
> +    aml_append(method, aml_name_decl("OFST", aml_int(0)));
> +
> +    /* prepare input package. */
> +    pkg = aml_package(1);
> +    aml_append(method, aml_store(aml_arg(0), aml_name("OFST")));
> +    aml_append(pkg, aml_name("OFST"));
> +
> +    /* call Read_FIT function. */
> +    call_result = aml_call5(NVDIMM_COMMON_DSM,
> +                            aml_touuid(NVDIMM_QEMU_RSVD_UUID),
> +                            aml_int(1) /* Revision 1 */,
> +                            aml_int(0x1) /* Read FIT */,
> +                            pkg, aml_int(NVDIMM_QEMU_RSVD_HANDLE_ROOT));
> +    aml_append(method, aml_store(call_result, buf));
> +
> +    /* handle _DSM result. */
> +    aml_append(method, aml_create_dword_field(buf,
> +               aml_int(0) /* offset at byte 0 */, "STAU"));
> +
> +    aml_append(method, aml_store(aml_name("STAU"),
> +                                 aml_name(NVDIMM_DSM_RFIT_STATUS)));
> +
> +     /* if something is wrong during _DSM. */
> +    ifcond = aml_equal(aml_int(0 /* Success */), aml_name("STAU"));
> +    ifctx = aml_if(aml_lnot(ifcond));
> +    aml_append(ifctx, aml_return(aml_buffer(0, NULL)));
> +    aml_append(method, ifctx);
> +
> +    aml_append(method, aml_store(aml_sizeof(buf), buf_size));
> +    aml_append(method, aml_subtract(buf_size,
> +               aml_int(4) /* the size of "STAU" */, buf_size));
> +
> +    /* if we read the end of fit. */
> +    ifctx = aml_if(aml_equal(buf_size, aml_int(0)));
> +    aml_append(ifctx, aml_return(aml_buffer(0, NULL)));
> +    aml_append(method, ifctx);
> +
> +    aml_append(method, aml_create_field(buf,
> +                            aml_int(4 * BITS_PER_BYTE), /* offset at byte 4.*/
> +                            aml_shiftleft(buf_size, aml_int(3)), "BUFF"));
> +    aml_append(method, aml_return(aml_name("BUFF")));
> +    aml_append(dev, method);
> +
> +    /* build _FIT. */
> +    method = aml_method("_FIT", 0, AML_SERIALIZED);
> +    offset = aml_local(3);
> +
> +    aml_append(method, aml_store(aml_buffer(0, NULL), fit));
> +    aml_append(method, aml_store(aml_int(0), offset));
> +
> +    whilectx = aml_while(aml_int(1));
> +    aml_append(whilectx, aml_store(aml_call1("RFIT", offset), buf));
> +    aml_append(whilectx, aml_store(aml_sizeof(buf), buf_size));
> +
> +    /*
> +     * if fit buffer was changed during RFIT, read from the beginning
> +     * again.
> +     */
> +    ifctx = aml_if(aml_equal(aml_name(NVDIMM_DSM_RFIT_STATUS),
> +                             aml_int(NVDIMM_DSM_RET_STATUS_FIT_CHANGED)));
> +    aml_append(ifctx, aml_store(aml_buffer(0, NULL), fit));
> +    aml_append(ifctx, aml_store(aml_int(0), offset));
> +    aml_append(whilectx, ifctx);
> +
> +    elsectx = aml_else();
> +
> +    /* finish fit read if no data is read out. */
> +    ifctx = aml_if(aml_equal(buf_size, aml_int(0)));
> +    aml_append(ifctx, aml_return(fit));
> +    aml_append(elsectx, ifctx);
> +
> +    /* update the offset. */
> +    aml_append(elsectx, aml_add(offset, buf_size, offset));
> +    /* append the data we read out to the fit buffer. */
> +    aml_append(elsectx, aml_concatenate(fit, buf, fit));
> +    aml_append(whilectx, elsectx);
> +    aml_append(method, whilectx);
> +
> +    aml_append(dev, method);
> +}
> +
>  static void nvdimm_build_nvdimm_devices(Aml *root_dev, uint32_t ram_slots)
>  {
>      uint32_t slot;
> @@ -1040,6 +1233,7 @@ static void nvdimm_build_ssdt(GArray *table_offsets, GArray *table_data,
>  
>      /* 0 is reserved for root device. */
>      nvdimm_build_device_dsm(dev, 0);
> +    nvdimm_build_fit_method(dev);
>  
>      nvdimm_build_nvdimm_devices(dev, ram_slots);
>  

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diff mbox

Patch

diff --git a/docs/specs/acpi_nvdimm.txt b/docs/specs/acpi_nvdimm.txt
index 0fdd251..63cb63f 100644
--- a/docs/specs/acpi_nvdimm.txt
+++ b/docs/specs/acpi_nvdimm.txt
@@ -65,8 +65,8 @@  _FIT(Firmware Interface Table)
    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 NVDIMM Implementation
+==========================
 QEMU uses 4 bytes IO Port starting from 0x0a18 and a RAM-based memory page
 for NVDIMM ACPI.
 
@@ -82,6 +82,16 @@  Memory:
    ACPI writes _DSM Input Data (based on the offset in the page):
    [0x0 - 0x3]: 4 bytes, NVDIMM Device Handle, 0 is reserved for NVDIMM
                 Root device.
+
+                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.
@@ -127,6 +137,47 @@  _DSM process diagram:
  | result from the page     |      |              |
  +--------------------------+      +--------------+
 
- _FIT implementation
- -------------------
- TODO (will fill it when nvdimm hotplug is introduced)
+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 the 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 length is
+   returned.
+
+   If it returns status code 0x100, OSPM should restart to read FIT (read
+   from offset 0 again).
diff --git a/hw/acpi/nvdimm.c b/hw/acpi/nvdimm.c
index d9d1ef7..f82ae4a 100644
--- a/hw/acpi/nvdimm.c
+++ b/hw/acpi/nvdimm.c
@@ -478,6 +478,22 @@  typedef struct NvdimmFuncSetLabelDataIn NvdimmFuncSetLabelDataIn;
 QEMU_BUILD_BUG_ON(sizeof(NvdimmFuncSetLabelDataIn) +
                   offsetof(NvdimmDsmIn, arg3) > 4096);
 
+struct NvdimmFuncReadFITIn {
+    uint32_t offset; /* the offset into FIT buffer. */
+} QEMU_PACKED;
+typedef struct NvdimmFuncReadFITIn NvdimmFuncReadFITIn;
+QEMU_BUILD_BUG_ON(sizeof(NvdimmFuncReadFITIn) +
+                  offsetof(NvdimmDsmIn, arg3) > 4096);
+
+struct NvdimmFuncReadFITOut {
+    /* the size of buffer filled by QEMU. */
+    uint32_t len;
+    uint32_t func_ret_status; /* return status code. */
+    uint8_t fit[0]; /* the FIT data. */
+} QEMU_PACKED;
+typedef struct NvdimmFuncReadFITOut NvdimmFuncReadFITOut;
+QEMU_BUILD_BUG_ON(sizeof(NvdimmFuncReadFITOut) > 4096);
+
 static void
 nvdimm_dsm_function0(uint32_t supported_func, hwaddr dsm_mem_addr)
 {
@@ -502,6 +518,73 @@  nvdimm_dsm_no_payload(uint32_t func_ret_status, hwaddr dsm_mem_addr)
 #define NVDIMM_DSM_RET_STATUS_UNSUPPORT      1 /* Not Supported */
 #define NVDIMM_DSM_RET_STATUS_NOMEMDEV       2 /* Non-Existing Memory Device */
 #define NVDIMM_DSM_RET_STATUS_INVALID        3 /* Invalid Input Parameters */
+#define NVDIMM_DSM_RET_STATUS_FIT_CHANGED    0x100 /* FIT Changed */
+
+#define NVDIMM_QEMU_RSVD_HANDLE_ROOT         0x10000
+
+/* Read FIT data, defined in docs/specs/acpi_nvdimm.txt. */
+static void nvdimm_dsm_func_read_fit(AcpiNVDIMMState *state, NvdimmDsmIn *in,
+                                     hwaddr dsm_mem_addr)
+{
+    NvdimmFitBuffer *fit_buf = &state->fit_buf;
+    NvdimmFuncReadFITIn *read_fit;
+    NvdimmFuncReadFITOut *read_fit_out;
+    GArray *fit;
+    uint32_t read_len = 0, func_ret_status, offset;
+    int size;
+
+    read_fit = (NvdimmFuncReadFITIn *)in->arg3;
+    offset = le32_to_cpu(read_fit->offset);
+
+    fit = fit_buf->fit;
+
+    nvdimm_debug("Read FIT: offset %#x FIT size %#x Dirty %s.\n",
+                 offset, fit->len, fit_buf->dirty ? "Yes" : "No");
+
+    /* It is the first time to read FIT. */
+    if (!offset) {
+        fit_buf->dirty = false;
+    } else if (fit_buf->dirty) { /* FIT has been changed during RFIT. */
+        func_ret_status = NVDIMM_DSM_RET_STATUS_FIT_CHANGED;
+        goto exit;
+    }
+
+    if (offset > fit->len) {
+        func_ret_status = NVDIMM_DSM_RET_STATUS_INVALID;
+        goto exit;
+    }
+
+    func_ret_status = NVDIMM_DSM_RET_STATUS_SUCCESS;
+    read_len = MIN(fit->len - offset, 4096 - sizeof(NvdimmFuncReadFITOut));
+
+exit:
+    size = sizeof(NvdimmFuncReadFITOut) + read_len;
+    read_fit_out = g_malloc(size);
+
+    read_fit_out->len = cpu_to_le32(size);
+    read_fit_out->func_ret_status = cpu_to_le32(func_ret_status);
+    memcpy(read_fit_out->fit, fit->data + offset, read_len);
+
+    cpu_physical_memory_write(dsm_mem_addr, read_fit_out, size);
+
+    g_free(read_fit_out);
+}
+
+static void
+nvdimm_dsm_handle_reserved_root_method(AcpiNVDIMMState *state,
+                                       NvdimmDsmIn *in, hwaddr dsm_mem_addr)
+{
+    switch (in->function) {
+    case 0x0:
+        nvdimm_dsm_function0(0x1 | 1 << 1 /* Read FIT */, dsm_mem_addr);
+        return;
+    case 0x1 /* Read FIT */:
+        nvdimm_dsm_func_read_fit(state, in, dsm_mem_addr);
+        return;
+    }
+
+    nvdimm_dsm_no_payload(NVDIMM_DSM_RET_STATUS_UNSUPPORT, dsm_mem_addr);
+}
 
 static void nvdimm_dsm_root(NvdimmDsmIn *in, hwaddr dsm_mem_addr)
 {
@@ -730,6 +813,7 @@  nvdimm_dsm_read(void *opaque, hwaddr addr, unsigned size)
 static void
 nvdimm_dsm_write(void *opaque, hwaddr addr, uint64_t val, unsigned size)
 {
+    AcpiNVDIMMState *state = opaque;
     NvdimmDsmIn *in;
     hwaddr dsm_mem_addr = val;
 
@@ -757,6 +841,11 @@  nvdimm_dsm_write(void *opaque, hwaddr addr, uint64_t val, unsigned size)
         goto exit;
     }
 
+    if (in->handle == NVDIMM_QEMU_RSVD_HANDLE_ROOT) {
+        nvdimm_dsm_handle_reserved_root_method(state, in, dsm_mem_addr);
+        goto exit;
+     }
+
      /* Handle 0 is reserved for NVDIMM Root Device. */
     if (!in->handle) {
         nvdimm_dsm_root(in, dsm_mem_addr);
@@ -809,9 +898,13 @@  void nvdimm_init_acpi_state(AcpiNVDIMMState *state, MemoryRegion *io,
 #define NVDIMM_DSM_OUT_BUF_SIZE "RLEN"
 #define NVDIMM_DSM_OUT_BUF      "ODAT"
 
+#define NVDIMM_DSM_RFIT_STATUS  "RSTA"
+
+#define NVDIMM_QEMU_RSVD_UUID   "648B9CF2-CDA1-4312-8AD9-49C4AF32BD62"
+
 static void nvdimm_build_common_dsm(Aml *dev)
 {
-    Aml *method, *ifctx, *function, *handle, *uuid, *dsm_mem;
+    Aml *method, *ifctx, *function, *handle, *uuid, *dsm_mem, *elsectx2;
     Aml *elsectx, *unsupport, *unpatched, *expected_uuid, *uuid_invalid;
     Aml *pckg, *pckg_index, *pckg_buf, *field, *dsm_out_buf, *dsm_out_buf_size;
     uint8_t byte_list[1];
@@ -900,9 +993,15 @@  static void nvdimm_build_common_dsm(Aml *dev)
                /* UUID for NVDIMM Root Device */, expected_uuid));
     aml_append(method, ifctx);
     elsectx = aml_else();
-    aml_append(elsectx, aml_store(
+    ifctx = aml_if(aml_equal(handle, aml_int(NVDIMM_QEMU_RSVD_HANDLE_ROOT)));
+    aml_append(ifctx, aml_store(aml_touuid(NVDIMM_QEMU_RSVD_UUID
+               /* UUID for QEMU internal use */), expected_uuid));
+    aml_append(elsectx, ifctx);
+    elsectx2 = aml_else();
+    aml_append(elsectx2, aml_store(
                aml_touuid("4309AC30-0D11-11E4-9191-0800200C9A66")
                /* UUID for NVDIMM Devices */, expected_uuid));
+    aml_append(elsectx, elsectx2);
     aml_append(method, elsectx);
 
     uuid_invalid = aml_lnot(aml_equal(uuid, expected_uuid));
@@ -982,6 +1081,100 @@  static void nvdimm_build_device_dsm(Aml *dev, uint32_t handle)
     aml_append(dev, method);
 }
 
+static void nvdimm_build_fit_method(Aml *dev)
+{
+    Aml *method, *pkg, *buf, *buf_size, *offset, *call_result;
+    Aml *whilectx, *ifcond, *ifctx, *elsectx, *fit;
+
+    buf = aml_local(0);
+    buf_size = aml_local(1);
+    fit = aml_local(2);
+
+    aml_append(dev, aml_name_decl(NVDIMM_DSM_RFIT_STATUS, aml_int(0)));
+
+    /* build helper function, RFIT. */
+    method = aml_method("RFIT", 1, AML_SERIALIZED);
+    aml_append(method, aml_name_decl("OFST", aml_int(0)));
+
+    /* prepare input package. */
+    pkg = aml_package(1);
+    aml_append(method, aml_store(aml_arg(0), aml_name("OFST")));
+    aml_append(pkg, aml_name("OFST"));
+
+    /* call Read_FIT function. */
+    call_result = aml_call5(NVDIMM_COMMON_DSM,
+                            aml_touuid(NVDIMM_QEMU_RSVD_UUID),
+                            aml_int(1) /* Revision 1 */,
+                            aml_int(0x1) /* Read FIT */,
+                            pkg, aml_int(NVDIMM_QEMU_RSVD_HANDLE_ROOT));
+    aml_append(method, aml_store(call_result, buf));
+
+    /* handle _DSM result. */
+    aml_append(method, aml_create_dword_field(buf,
+               aml_int(0) /* offset at byte 0 */, "STAU"));
+
+    aml_append(method, aml_store(aml_name("STAU"),
+                                 aml_name(NVDIMM_DSM_RFIT_STATUS)));
+
+     /* if something is wrong during _DSM. */
+    ifcond = aml_equal(aml_int(0 /* Success */), aml_name("STAU"));
+    ifctx = aml_if(aml_lnot(ifcond));
+    aml_append(ifctx, aml_return(aml_buffer(0, NULL)));
+    aml_append(method, ifctx);
+
+    aml_append(method, aml_store(aml_sizeof(buf), buf_size));
+    aml_append(method, aml_subtract(buf_size,
+               aml_int(4) /* the size of "STAU" */, buf_size));
+
+    /* if we read the end of fit. */
+    ifctx = aml_if(aml_equal(buf_size, aml_int(0)));
+    aml_append(ifctx, aml_return(aml_buffer(0, NULL)));
+    aml_append(method, ifctx);
+
+    aml_append(method, aml_create_field(buf,
+                            aml_int(4 * BITS_PER_BYTE), /* offset at byte 4.*/
+                            aml_shiftleft(buf_size, aml_int(3)), "BUFF"));
+    aml_append(method, aml_return(aml_name("BUFF")));
+    aml_append(dev, method);
+
+    /* build _FIT. */
+    method = aml_method("_FIT", 0, AML_SERIALIZED);
+    offset = aml_local(3);
+
+    aml_append(method, aml_store(aml_buffer(0, NULL), fit));
+    aml_append(method, aml_store(aml_int(0), offset));
+
+    whilectx = aml_while(aml_int(1));
+    aml_append(whilectx, aml_store(aml_call1("RFIT", offset), buf));
+    aml_append(whilectx, aml_store(aml_sizeof(buf), buf_size));
+
+    /*
+     * if fit buffer was changed during RFIT, read from the beginning
+     * again.
+     */
+    ifctx = aml_if(aml_equal(aml_name(NVDIMM_DSM_RFIT_STATUS),
+                             aml_int(NVDIMM_DSM_RET_STATUS_FIT_CHANGED)));
+    aml_append(ifctx, aml_store(aml_buffer(0, NULL), fit));
+    aml_append(ifctx, aml_store(aml_int(0), offset));
+    aml_append(whilectx, ifctx);
+
+    elsectx = aml_else();
+
+    /* finish fit read if no data is read out. */
+    ifctx = aml_if(aml_equal(buf_size, aml_int(0)));
+    aml_append(ifctx, aml_return(fit));
+    aml_append(elsectx, ifctx);
+
+    /* update the offset. */
+    aml_append(elsectx, aml_add(offset, buf_size, offset));
+    /* append the data we read out to the fit buffer. */
+    aml_append(elsectx, aml_concatenate(fit, buf, fit));
+    aml_append(whilectx, elsectx);
+    aml_append(method, whilectx);
+
+    aml_append(dev, method);
+}
+
 static void nvdimm_build_nvdimm_devices(Aml *root_dev, uint32_t ram_slots)
 {
     uint32_t slot;
@@ -1040,6 +1233,7 @@  static void nvdimm_build_ssdt(GArray *table_offsets, GArray *table_data,
 
     /* 0 is reserved for root device. */
     nvdimm_build_device_dsm(dev, 0);
+    nvdimm_build_fit_method(dev);
 
     nvdimm_build_nvdimm_devices(dev, ram_slots);