On 11/04/2016 12:13 AM, Igor Mammedov wrote:
On Thu, 3 Nov 2016 22:53:43 +0800
Xiao Guangrong <guangrong.xiao@xxxxxxxxxxxxxxx> wrote:
On 11/03/2016 10:49 PM, Igor Mammedov wrote:
On Thu, 3 Nov 2016 21:02:22 +0800
Xiao Guangrong <guangrong.xiao@xxxxxxxxxxxxxxx> wrote:
On 11/03/2016 09:00 PM, Igor Mammedov wrote:
just drop this and describe properly 'len' in spec section
i.e. len: length of entire returned data (including the header)
Okay, i will change the spec like this:
QEMU Writes Output Data (based on the offset in the page):
[0x0 - 0x3]: 4 bytes, length of entire returned data
(including the header)
And drop the length field in Read_Fit return buffer, doc
the fit buffer like this:
+----------+--------+--------+-------------------------------------------+
| Field | Length | Offset |
Description |
+----------+--------+--------+-------------------------------------------+
you need to add length here, otherwise this table is not correct
Ah, so i am confused.
struct NvdimmFuncReadFITOut definition is based on the layout of
Read_FI output. You suggested to drop the length filed in
NvdimmFuncReadFITOut but keep it in the layout, it is not
consistent.
I missed something?
+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;
--------------------------------
| field | len | off | desc...
--------------------------------
| length | 4 | 0 | ....
--------------------------------
| status | 4 | 4 | ....
--------------------------------
| fit data | ................
i.e. you were forgetting to add length in spec so offsets were wrong
even for described fields.
We can not do this.
@len is used by QEMU emulation to count the size of the buffer that
_DSM should return. It's only used in NVDIMM_COMMON_DSM method which
is shared by the DSM method from VM and Read_Fit.
spec describes buffer layout independently from AML that uses it,
so it should describe whole data structure.
Then it's upto guest how to read this data, it could be QEMU generated
AML (as it's here) or some other driver or even BIOS.
However, what we are talking about is Read_FIT method, so this is
the layout of Read_FIT output rather than all memory in the dsm page.
Actually, in the spec we already have documented the common len field:
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
Also, i really do not hope to use this field to count the buffer size
returned by Read_FIT, we'd try the best to reuse existing DSM method
(NVDIMM_COMMON_DSM), i.e, treat Read_FIT as normal DSM method.
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