Re: Support for CXL v3.0 spec with QEMU

[Gregory Price <gregory.price@memverge.com>]

On Fri, Sep 01, 2023 at 07:33:57PM +0530, Ravi Kanth wrote:
> Thanks Jonathan. We built the custom kernel and were able to run the
> test tool successfully and get the data.
> 
> However when we modify the code to send raw commands, we are not able
> to send raw commands to the driver. We always see ENOPERM from the
> driver. Below is the code snippet. Should we enable some settings or
> from a code perspective should changes be made?
> 
> From CXL driver code perspective, we see that ENOPERM can only be
> returned by cxl_mem_raw_command_allowed(). Not really sure why the raw
> command is not able to go through but the MEM
> command(CXL_MEM_COMMAND_ID_INFO_STAT_IDENTIFY) is able to run
> successfully.
> 
> Can you please help us here?
> 
> Code snippet:
>   cmd.id = CXL_MEM_COMMAND_ID_RAW;
>   cmd.raw.opcode= 0x0001; /*This is a Identify (Opcode 0001h) per CXL spec */
>   cmd.out.size = sizeof(is_identify);
>   cmd.out.payload = (__u64)&is_identify;
> 
>   printf("sending identify command...\n");
>   printf("cmd.id:%x cmd.raw.opcode:%x\n",cmd.id,cmd.raw.opcode);
>   printf("cmd.raw.rsvd:%d\n",cmd.raw.rsvd);
>   rc = ioctl(fd, CXL_MEM_SEND_COMMAND, &cmd);
> 
> Appreciate your help all along.
> 
> Ravi
> 

raw commands are not allowed by default, you must turn on
CONFIG_CXL_MEM_RAW_COMMANDS in the kernel build config.

~Gregory