From mboxrd@z Thu Jan  1 00:00:00 1970
From: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Subject: Re: [PATCH v4 28/33] nvdimm acpi: support DSM_FUN_IMPLEMENTED
 function
Date: Wed, 21 Oct 2015 00:26:35 +0800
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On 10/20/2015 11:51 PM, Stefan Hajnoczi wrote:
> On Mon, Oct 19, 2015 at 08:54:14AM +0800, Xiao Guangrong wrote:
>> +exit:
>> +    /* Write our output result to dsm memory. */
>> +    ((dsm_out *)dsm_ram_addr)->len =3D out->len;
>
> Missing byteswap?
>
> I thought you were going to remove this field because it wasn't neede=
d
> by the guest.
>

The @len is the size of _DSM result buffer, for example, for the functi=
on of
DSM_FUN_IMPLEMENTED the result buffer is 8 bytes, and for
DSM_DEV_FUN_NAMESPACE_LABEL_SIZE the buffer size is 4 bytes. It tells A=
SL code
how much size of memory we need to return to the _DSM caller.

In _DSM code, it's handled like this:

"RLEN" is @len, =E2=80=9COBUF=E2=80=9D is the left memory in DSM page.

         /* get @len*/
         aml_append(method, aml_store(aml_name("RLEN"), aml_local(6)));
         /* @len << 3 to get bits. */
         aml_append(method, aml_store(aml_shiftleft(aml_local(6),
                                        aml_int(3)), aml_local(6)));

         /* get @len << 3 bits from OBUF, and return it to the caller. =
*/
         aml_append(method, aml_create_field(aml_name("ODAT"), aml_int(=
0),
                                             aml_local(6) , "OBUF"));

Since @len is our internally used, it's not return to guest, so i did n=
ot do
byteswap here.